0.pre7.58:
[sbcl.git] / src / runtime / gencgc.c
index 65ddf79..b8d18d7 100644 (file)
  */
 
 /*
- * $Header$
- */
-
-/*
  * For a review of garbage collection techniques (e.g. generational
  * GC) and terminology (e.g. "scavenging") see Paul R. Wilson,
  * "Uniprocessor Garbage Collection Techniques". As of 20000618, this
  *   <ftp://ftp.cs.utexas.edu/pub/garbage/bigsurv.ps>.
  */
 
-/*
- * FIXME: GC :FULL T seems to be unable to recover a lot of unused
- * space. After cold init is complete, GC :FULL T gets us down to
- * about 44 Mb total used, but PURIFY gets us down to about 17 Mb
- * total used.
- */
-
 #include <stdio.h>
 #include <signal.h>
 #include "runtime.h"
 #include "sbcl.h"
 #include "os.h"
+#include "interr.h"
 #include "globals.h"
 #include "interrupt.h"
 #include "validate.h"
 #include "lispregs.h"
+#include "arch.h"
 #include "gc.h"
 #include "gencgc.h"
 
@@ -56,8 +47,8 @@ void do_pending_interrupt(void);
  */
 
 /* the number of actual generations. (The number of 'struct
- * generation' objects is one more than this, because one serves as
- * scratch when GC'ing.) */
+ * generation' objects is one more than this, because one object
+ * serves as scratch when GC'ing.) */
 #define NUM_GENERATIONS 6
 
 /* Should we use page protection to help avoid the scavenging of pages
@@ -66,10 +57,13 @@ boolean enable_page_protection = 1;
 
 /* Should we unmap a page and re-mmap it to have it zero filled? */
 #if defined(__FreeBSD__) || defined(__OpenBSD__)
-/* Note: this can waste a lot of swap on FreeBSD so don't unmap there.
+/* comment from cmucl-2.4.8: This can waste a lot of swap on FreeBSD
+ * so don't unmap there.
  *
- * Presumably this behavior exists on OpenBSD too, so don't unmap
- * there either. -- WHN 20000727 */
+ * The CMU CL comment didn't specify a version, but was probably an
+ * old version of FreeBSD (pre-4.0), so this might no longer be true.
+ * OTOH, if it is true, this behavior might exist on OpenBSD too, so
+ * for now we don't unmap there either. -- WHN 2001-04-07 */
 boolean gencgc_unmap_zero = 0;
 #else
 boolean gencgc_unmap_zero = 1;
@@ -77,11 +71,6 @@ boolean gencgc_unmap_zero = 1;
 
 /* the minimum size (in bytes) for a large object*/
 unsigned large_object_size = 4 * 4096;
-
-/* Should we filter stack/register pointers? This could reduce the
- * number of invalid pointers accepted. KLUDGE: It will probably
- * degrades interrupt safety during object initialization. */
-boolean enable_pointer_filter = 1;
 \f
 /*
  * debugging
@@ -164,8 +153,8 @@ struct page page_table[NUM_PAGES];
 static void *heap_base = NULL;
 
 /* Calculate the start address for the given page number. */
-inline void
-*page_address(int page_num)
+inline void *
+page_address(int page_num)
 {
     return (heap_base + (page_num * 4096));
 }
@@ -189,10 +178,10 @@ find_page_index(void *addr)
 /* a structure to hold the state of a generation */
 struct generation {
 
-    /* the first page that gc_alloc checks on its next call */
+    /* the first page that gc_alloc() checks on its next call */
     int alloc_start_page;
 
-    /* the first page that gc_alloc_unboxed checks on its next call */
+    /* the first page that gc_alloc_unboxed() checks on its next call */
     int alloc_unboxed_start_page;
 
     /* the first page that gc_alloc_large (boxed) considers on its next
@@ -269,28 +258,28 @@ static int
 count_write_protect_generation_pages(int generation)
 {
     int i;
-    int cnt = 0;
+    int count = 0;
 
     for (i = 0; i < last_free_page; i++)
        if ((page_table[i].allocated != FREE_PAGE)
            && (page_table[i].gen == generation)
            && (page_table[i].write_protected == 1))
-           cnt++;
-    return(cnt);
+           count++;
+    return count;
 }
 
-/* Count the number of pages within the given generation */
+/* Count the number of pages within the given generation. */
 static int
 count_generation_pages(int generation)
 {
     int i;
-    int cnt = 0;
+    int count = 0;
 
     for (i = 0; i < last_free_page; i++)
        if ((page_table[i].allocated != 0)
            && (page_table[i].gen == generation))
-           cnt++;
-    return(cnt);
+           count++;
+    return count;
 }
 
 /* Count the number of dont_move pages. */
@@ -298,23 +287,22 @@ static int
 count_dont_move_pages(void)
 {
     int i;
-    int cnt = 0;
-
-    for (i = 0; i < last_free_page; i++)
-       if ((page_table[i].allocated != 0)
-           && (page_table[i].dont_move != 0))
-           cnt++;
-    return(cnt);
+    int count = 0;
+    for (i = 0; i < last_free_page; i++) {
+       if ((page_table[i].allocated != 0) && (page_table[i].dont_move != 0)) {
+           ++count;
+       }
+    }
+    return count;
 }
 
 /* Work through the pages and add up the number of bytes used for the
  * given generation. */
 static int
-generation_bytes_allocated (int gen)
+count_generation_bytes_allocated (int gen)
 {
     int i;
     int result = 0;
-
     for (i = 0; i < last_free_page; i++) {
        if ((page_table[i].allocated != 0) && (page_table[i].gen == gen))
            result += page_table[i].bytes_used;
@@ -365,27 +353,30 @@ print_generation_stats(int verbose) /* FIXME: should take FILE argument */
 
        for (j = 0; j < last_free_page; j++)
            if (page_table[j].gen == i) {
+
                /* Count the number of boxed pages within the given
-                * generation */
-               if (page_table[j].allocated == BOXED_PAGE)
+                * generation. */
+               if (page_table[j].allocated == BOXED_PAGE) {
                    if (page_table[j].large_object)
                        large_boxed_cnt++;
                    else
                        boxed_cnt++;
-       
+               }
+
                /* Count the number of unboxed pages within the given
-                * generation */
-               if (page_table[j].allocated == UNBOXED_PAGE)
+                * generation. */
+               if (page_table[j].allocated == UNBOXED_PAGE) {
                    if (page_table[j].large_object)
                        large_unboxed_cnt++;
                    else
                        unboxed_cnt++;
+               }
            }
 
        gc_assert(generations[i].bytes_allocated
-                 == generation_bytes_allocated(i));
+                 == count_generation_bytes_allocated(i));
        fprintf(stderr,
-               "   %8d: %5d %5d %5d %5d %8d %5d %8d %4d %3d %7.4lf\n",
+               "   %8d: %5d %5d %5d %5d %8d %5d %8d %4d %3d %7.4f\n",
                i,
                boxed_cnt, unboxed_cnt, large_boxed_cnt, large_unboxed_cnt,
                generations[i].bytes_allocated,
@@ -396,7 +387,7 @@ print_generation_stats(int verbose) /* FIXME: should take FILE argument */
                generations[i].num_gc,
                gen_av_mem_age(i));
     }
-    fprintf(stderr,"   Total bytes allocated=%d\n", bytes_allocated);
+    fprintf(stderr,"   Total bytes allocated=%ld\n", bytes_allocated);
 
     fpu_restore(fpu_state);
 }
@@ -470,7 +461,7 @@ static int gc_alloc_generation;
  * keeps the allocation contiguous when scavenging the newspace.
  *
  * The alloc_region should have been closed by a call to
- * gc_alloc_update_page_tables, and will thus be in an empty state.
+ * gc_alloc_update_page_tables(), and will thus be in an empty state.
  *
  * To assist the scavenging functions write-protected pages are not
  * used. Free pages should not be write-protected.
@@ -522,7 +513,10 @@ gc_alloc_new_region(int nbytes, int unboxed, struct alloc_region *alloc_region)
        first_page = restart_page;
 
        /* First search for a page with at least 32 bytes free, which is
-        * not write-protected, and which is not marked dont_move. */
+        * not write-protected, and which is not marked dont_move.
+        *
+        * FIXME: This looks extremely similar, perhaps identical, to
+        * code in gc_alloc_large(). It should be shared somehow. */
        while ((first_page < NUM_PAGES)
               && (page_table[first_page].allocated != FREE_PAGE) /* not free page */
               && ((unboxed &&
@@ -585,7 +579,7 @@ gc_alloc_new_region(int nbytes, int unboxed, struct alloc_region *alloc_region)
     /* Check for a failure. */
     if ((restart_page >= NUM_PAGES) && (bytes_found < nbytes)) {
        fprintf(stderr,
-               "Argh! gc_alloc_new_region failed on restart_page, nbytes=%d.\n",
+               "Argh! gc_alloc_new_region() failed on restart_page, nbytes=%d.\n",
                nbytes);
        print_generation_stats(1);
        lose(NULL);
@@ -593,7 +587,7 @@ gc_alloc_new_region(int nbytes, int unboxed, struct alloc_region *alloc_region)
 
     /*
     FSHOW((stderr,
-          "/gc_alloc_new_region gen %d: %d bytes: pages %d to %d: addr=%x\n",
+          "/gc_alloc_new_region() gen %d: %d bytes: pages %d to %d: addr=%x\n",
           gc_alloc_generation,
           bytes_found,
           first_page,
@@ -690,7 +684,7 @@ struct new_area {
     int  size;
 };
 static struct new_area (*new_areas)[];
-static new_areas_index;
+static int new_areas_index;
 int max_new_areas;
 
 /* Add a new area to new_areas. */
@@ -778,7 +772,7 @@ gc_alloc_update_page_tables(int unboxed, struct alloc_region *alloc_region)
 
     /*
     FSHOW((stderr,
-          "/gc_alloc_update_page_tables to gen %d:\n",
+          "/gc_alloc_update_page_tables() to gen %d:\n",
           gc_alloc_generation));
     */
 
@@ -790,7 +784,7 @@ gc_alloc_update_page_tables(int unboxed, struct alloc_region *alloc_region)
 
     next_page = first_page+1;
 
-    /* Skip if no bytes were allocated */
+    /* Skip if no bytes were allocated. */
     if (alloc_region->free_pointer != alloc_region->start_addr) {
        orig_first_page_bytes_used = page_table[first_page].bytes_used;
 
@@ -801,7 +795,7 @@ gc_alloc_update_page_tables(int unboxed, struct alloc_region *alloc_region)
        /* Update the first page. */
 
        /* If the page was free then set up the gen, and
-           first_object_offset. */
+        * first_object_offset. */
        if (page_table[first_page].bytes_used == 0)
            gc_assert(page_table[first_page].first_object_offset == 0);
 
@@ -814,8 +808,8 @@ gc_alloc_update_page_tables(int unboxed, struct alloc_region *alloc_region)
 
        byte_cnt = 0;
 
-       /* Calc. the number of bytes used in this page. This is not always
-          the number of new bytes, unless it was free. */
+       /* Calculate the number of bytes used in this page. This is not
+        * always the number of new bytes, unless it was free. */
        more = 0;
        if ((bytes_used = (alloc_region->free_pointer - page_address(first_page)))>4096) {
            bytes_used = 4096;
@@ -825,9 +819,9 @@ gc_alloc_update_page_tables(int unboxed, struct alloc_region *alloc_region)
        byte_cnt += bytes_used;
 
 
-       /* All the rest of the pages should be free. Need to set their
-          first_object_offset pointer to the start of the region, and set
-          the bytes_used. */
+       /* All the rest of the pages should be free. We need to set their
+        * first_object_offset pointer to the start of the region, and set
+        * the bytes_used. */
        while (more) {
            if (unboxed)
                gc_assert(page_table[next_page].allocated == UNBOXED_PAGE);
@@ -860,7 +854,7 @@ gc_alloc_update_page_tables(int unboxed, struct alloc_region *alloc_region)
        gc_assert((byte_cnt- orig_first_page_bytes_used) == region_size);
 
        /* Set the generations alloc restart page to the last page of
-          the region. */
+        * the region. */
        if (unboxed)
            generations[gc_alloc_generation].alloc_unboxed_start_page =
                next_page-1;
@@ -877,12 +871,12 @@ gc_alloc_update_page_tables(int unboxed, struct alloc_region *alloc_region)
               region_size,
               gc_alloc_generation));
        */
-    }
-    else
-       /* No bytes allocated. Unallocate the first_page if there are 0
-          bytes_used. */
+    } else {
+       /* There are no bytes allocated. Unallocate the first_page if
+        * there are 0 bytes_used. */
        if (page_table[first_page].bytes_used == 0)
            page_table[first_page].allocated = FREE_PAGE;
+    }
 
     /* Unallocate any unused pages. */
     while (next_page <= alloc_region->last_page) {
@@ -902,8 +896,8 @@ gc_alloc_update_page_tables(int unboxed, struct alloc_region *alloc_region)
 static inline void *gc_quick_alloc(int nbytes);
 
 /* Allocate a possibly large object. */
-static void
-*gc_alloc_large(int nbytes, int unboxed, struct alloc_region *alloc_region)
+static void *
+gc_alloc_large(int nbytes, int unboxed, struct alloc_region *alloc_region)
 {
     int first_page;
     int last_page;
@@ -925,7 +919,7 @@ static void
 
     /*
     FSHOW((stderr,
-          "/gc_alloc_large for %d bytes from gen %d\n",
+          "/gc_alloc_large() for %d bytes from gen %d\n",
           nbytes, gc_alloc_generation));
     */
 
@@ -944,12 +938,15 @@ static void
        the current boxed free region. XX could probably keep a page
        index ahead of the current region and bumped up here to save a
        lot of re-scanning. */
-    if (unboxed)
-       restart_page = generations[gc_alloc_generation].alloc_large_unboxed_start_page;
-    else
+    if (unboxed) {
+       restart_page =
+           generations[gc_alloc_generation].alloc_large_unboxed_start_page;
+    } else {
        restart_page = generations[gc_alloc_generation].alloc_large_start_page;
-    if (restart_page <= alloc_region->last_page)
+    }
+    if (restart_page <= alloc_region->last_page) {
        restart_page = alloc_region->last_page+1;
+    }
 
     do {
        first_page = restart_page;
@@ -959,6 +956,9 @@ static void
                   && (page_table[first_page].allocated != FREE_PAGE))
                first_page++;
        else
+           /* FIXME: This looks extremely similar, perhaps identical,
+            * to code in gc_alloc_new_region(). It should be shared
+            * somehow. */
            while ((first_page < NUM_PAGES)
                   && (page_table[first_page].allocated != FREE_PAGE)
                   && ((unboxed &&
@@ -1026,7 +1026,7 @@ static void
     /*
     if (large)
        FSHOW((stderr,
-              "/gc_alloc_large gen %d: %d of %d bytes: from pages %d to %d: addr=%x\n",
+              "/gc_alloc_large() gen %d: %d of %d bytes: from pages %d to %d: addr=%x\n",
               gc_alloc_generation,
               nbytes,
               bytes_found,
@@ -1127,11 +1127,11 @@ static void
     return((void *)(page_address(first_page)+orig_first_page_bytes_used));
 }
 
-/* Allocate bytes from the boxed_region. It first checks if there is
- * room, if not then it calls gc_alloc_new_region to find a new region
- * with enough space. A pointer to the start of the region is returned. */
-static void
-*gc_alloc(int nbytes)
+/* Allocate bytes from the boxed_region. First checks whether there is
+ * room. If not then call gc_alloc_new_region() to find a new region
+ * with enough space. Return a pointer to the start of the region. */
+static void *
+gc_alloc(int nbytes)
 {
     void *new_free_pointer;
 
@@ -1195,13 +1195,14 @@ static void
 
     /* shouldn't happen */
     gc_assert(0);
+    return((void *) NIL); /* dummy value: return something ... */
 }
 
 /* Allocate space from the boxed_region. If there is not enough free
  * space then call gc_alloc to do the job. A pointer to the start of
  * the region is returned. */
-static inline void
-*gc_quick_alloc(int nbytes)
+static inline void *
+gc_quick_alloc(int nbytes)
 {
     void *new_free_pointer;
 
@@ -1209,22 +1210,22 @@ static inline void
     new_free_pointer = boxed_region.free_pointer + nbytes;
 
     if (new_free_pointer <= boxed_region.end_addr) {
-       /* If so then allocate from the current region. */
+       /* Allocate from the current region. */
        void  *new_obj = boxed_region.free_pointer;
        boxed_region.free_pointer = new_free_pointer;
        return((void *)new_obj);
+    } else {
+       /* Let full gc_alloc() handle it. */
+       return gc_alloc(nbytes);
     }
-
-    /* Else call gc_alloc */
-    return (gc_alloc(nbytes));
 }
 
 /* Allocate space for the boxed object. If it is a large object then
  * do a large alloc else allocate from the current region. If there is
- * not enough free space then call gc_alloc to do the job. A pointer
+ * not enough free space then call gc_alloc() to do the job. A pointer
  * to the start of the region is returned. */
-static inline void
-*gc_quick_alloc_large(int nbytes)
+static inline void *
+gc_quick_alloc_large(int nbytes)
 {
     void *new_free_pointer;
 
@@ -1239,19 +1240,19 @@ static inline void
        void *new_obj = boxed_region.free_pointer;
        boxed_region.free_pointer = new_free_pointer;
        return((void *)new_obj);
+    } else {
+       /* Let full gc_alloc() handle it. */
+       return gc_alloc(nbytes);
     }
-
-    /* Else call gc_alloc */
-    return (gc_alloc(nbytes));
 }
 
-static void
-*gc_alloc_unboxed(int nbytes)
+static void *
+gc_alloc_unboxed(int nbytes)
 {
     void *new_free_pointer;
 
     /*
-    FSHOW((stderr, "/gc_alloc_unboxed %d\n", nbytes));
+    FSHOW((stderr, "/gc_alloc_unboxed() %d\n", nbytes));
     */
 
     /* Check whether there is room in the current region. */
@@ -1289,7 +1290,7 @@ static void
     /* Set up a new region. */
     gc_alloc_new_region(nbytes, 1, &unboxed_region);
 
-    /* Should now be enough room. */
+    /* (There should now be enough room.) */
 
     /* Check whether there is room in the current region. */
     new_free_pointer = unboxed_region.free_pointer + nbytes;
@@ -1313,10 +1314,11 @@ static void
 
     /* shouldn't happen? */
     gc_assert(0);
+    return((void *) NIL); /* dummy value: return something ... */
 }
 
-static inline void
-*gc_quick_alloc_unboxed(int nbytes)
+static inline void *
+gc_quick_alloc_unboxed(int nbytes)
 {
     void *new_free_pointer;
 
@@ -1329,19 +1331,19 @@ static inline void
        unboxed_region.free_pointer = new_free_pointer;
 
        return((void *)new_obj);
+    } else {
+       /* Let general gc_alloc_unboxed() handle it. */
+       return gc_alloc_unboxed(nbytes);
     }
-
-    /* Else call gc_alloc */
-    return (gc_alloc_unboxed(nbytes));
 }
 
 /* Allocate space for the object. If it is a large object then do a
  * large alloc else allocate from the current region. If there is not
- * enough free space then call gc_alloc to do the job.
+ * enough free space then call general gc_alloc_unboxed() to do the job.
  *
  * A pointer to the start of the region is returned. */
-static inline void
-*gc_quick_alloc_large_unboxed(int nbytes)
+static inline void *
+gc_quick_alloc_large_unboxed(int nbytes)
 {
     void *new_free_pointer;
 
@@ -1350,17 +1352,15 @@ static inline void
 
     /* Check whether there is room in the current region. */
     new_free_pointer = unboxed_region.free_pointer + nbytes;
-
     if (new_free_pointer <= unboxed_region.end_addr) {
-       /* If so then allocate from the current region. */
+       /* Allocate from the current region. */
        void *new_obj = unboxed_region.free_pointer;
        unboxed_region.free_pointer = new_free_pointer;
-
        return((void *)new_obj);
+    } else {
+       /* Let full gc_alloc() handle it. */
+       return gc_alloc_unboxed(nbytes);
     }
-
-    /* Else call gc_alloc. */
-    return (gc_alloc_unboxed(nbytes));
 }
 \f
 /*
@@ -1409,18 +1409,18 @@ copy_object(lispobj object, int nwords)
     lispobj *new;
     lispobj *source, *dest;
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
     gc_assert(from_space_p(object));
     gc_assert((nwords & 0x01) == 0);
 
     /* Get tag of object. */
-    tag = LowtagOf(object);
+    tag = lowtag_of(object);
 
     /* Allocate space. */
     new = gc_quick_alloc(nwords*4);
 
     dest = new;
-    source = (lispobj *) PTR(object);
+    source = (lispobj *) native_pointer(object);
 
     /* Copy the object. */
     while (nwords > 0) {
@@ -1449,7 +1449,7 @@ copy_large_object(lispobj object, int nwords)
     lispobj *source, *dest;
     int first_page;
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
     gc_assert(from_space_p(object));
     gc_assert((nwords & 0x01) == 0);
 
@@ -1549,13 +1549,13 @@ copy_large_object(lispobj object, int nwords)
        return(object);
     } else {
        /* Get tag of object. */
-       tag = LowtagOf(object);
+       tag = lowtag_of(object);
 
        /* Allocate space. */
        new = gc_quick_alloc_large(nwords*4);
 
        dest = new;
-       source = (lispobj *) PTR(object);
+       source = (lispobj *) native_pointer(object);
 
        /* Copy the object. */
        while (nwords > 0) {
@@ -1579,18 +1579,18 @@ copy_unboxed_object(lispobj object, int nwords)
     lispobj *new;
     lispobj *source, *dest;
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
     gc_assert(from_space_p(object));
     gc_assert((nwords & 0x01) == 0);
 
     /* Get tag of object. */
-    tag = LowtagOf(object);
+    tag = lowtag_of(object);
 
     /* Allocate space. */
     new = gc_quick_alloc_unboxed(nwords*4);
 
     dest = new;
-    source = (lispobj *) PTR(object);
+    source = (lispobj *) native_pointer(object);
 
     /* Copy the object. */
     while (nwords > 0) {
@@ -1624,7 +1624,7 @@ copy_large_unboxed_object(lispobj object, int nwords)
     lispobj *source, *dest;
     int first_page;
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
     gc_assert(from_space_p(object));
     gc_assert((nwords & 0x01) == 0);
 
@@ -1713,13 +1713,13 @@ copy_large_unboxed_object(lispobj object, int nwords)
     }
     else {
        /* Get tag of object. */
-       tag = LowtagOf(object);
+       tag = lowtag_of(object);
 
        /* Allocate space. */
        new = gc_quick_alloc_large_unboxed(nwords*4);
 
        dest = new;
-       source = (lispobj *) PTR(object);
+       source = (lispobj *) native_pointer(object);
 
        /* Copy the object. */
        while (nwords > 0) {
@@ -1739,145 +1739,84 @@ copy_large_unboxed_object(lispobj object, int nwords)
  * scavenging
  */
 
-#define DIRECT_SCAV 0
-
+/* FIXME: Most calls end up going to some trouble to compute an
+ * 'n_words' value for this function. The system might be a little
+ * simpler if this function used an 'end' parameter instead. */
 static void
-scavenge(lispobj *start, long nwords)
+scavenge(lispobj *start, long n_words)
 {
-    while (nwords > 0) {
-       lispobj object;
-       int type, words_scavenged;
+    lispobj *end = start + n_words;
+    lispobj *object_ptr;
+    int n_words_scavenged;
+    
+    for (object_ptr = start;
+        object_ptr < end;
+        object_ptr += n_words_scavenged) {
 
-       object = *start;
+       lispobj object = *object_ptr;
        
-/*     FSHOW((stderr, "Scavenge: %p, %ld\n", start, nwords)); */
-
        gc_assert(object != 0x01); /* not a forwarding pointer */
 
-#if DIRECT_SCAV
-       type = TypeOf(object);
-       words_scavenged = (scavtab[type])(start, object);
-#else
-       if (Pointerp(object)) {
-           /* It's a pointer. */
+       if (is_lisp_pointer(object)) {
            if (from_space_p(object)) {
-               /* It currently points to old space. Check for a forwarding
-                * pointer. */
-               lispobj *ptr = (lispobj *)PTR(object);
+               /* It currently points to old space. Check for a
+                * forwarding pointer. */
+               lispobj *ptr = (lispobj *)native_pointer(object);
                lispobj first_word = *ptr;
-       
                if (first_word == 0x01) {
                    /* Yes, there's a forwarding pointer. */
-                   *start = ptr[1];
-                   words_scavenged = 1;
-               }
-               else
+                   *object_ptr = ptr[1];
+                   n_words_scavenged = 1;
+               } else {
                    /* Scavenge that pointer. */
-                   words_scavenged = (scavtab[TypeOf(object)])(start, object);
+                   n_words_scavenged =
+                       (scavtab[widetag_of(object)])(object_ptr, object);
+               }
            } else {
-               /* It points somewhere other than oldspace. Leave it alone. */
-               words_scavenged = 1;
+               /* It points somewhere other than oldspace. Leave it
+                * alone. */
+               n_words_scavenged = 1;
            }
+       } else if ((object & 3) == 0) {
+           /* It's a fixnum: really easy.. */
+           n_words_scavenged = 1;
        } else {
-           if ((object & 3) == 0) {
-               /* It's a fixnum: really easy.. */
-               words_scavenged = 1;
-           } else {
-               /* It's some sort of header object or another. */
-               words_scavenged = (scavtab[TypeOf(object)])(start, object);
-           }
+           /* It's some sort of header object or another. */
+           n_words_scavenged =
+               (scavtab[widetag_of(object)])(object_ptr, object);
        }
-#endif
-
-       start += words_scavenged;
-       nwords -= words_scavenged;
     }
-    gc_assert(nwords == 0);
+    gc_assert(object_ptr == end);
 }
-
 \f
 /*
  * code and code-related objects
  */
 
-#define RAW_ADDR_OFFSET (6*sizeof(lispobj) - type_FunctionPointer)
+/* FIXME: (1) Shouldn't this be defined in sbcl.h? */
+#define FUN_RAW_ADDR_OFFSET (6*sizeof(lispobj) - FUN_POINTER_LOWTAG)
 
-static lispobj trans_function_header(lispobj object);
+static lispobj trans_fun_header(lispobj object);
 static lispobj trans_boxed(lispobj object);
 
-#if DIRECT_SCAV
-static int
-scav_function_pointer(lispobj *where, lispobj object)
-{
-    gc_assert(Pointerp(object));
-
-    if (from_space_p(object)) {
-       lispobj first, *first_pointer;
-
-       /* object is a pointer into from space. Check to see whether
-        * it has been forwarded. */
-       first_pointer = (lispobj *) PTR(object);
-       first = *first_pointer;
-
-       if (first == 0x01) {
-           /* Forwarded */
-           *where = first_pointer[1];
-           return 1;
-       }
-       else {
-           int type;
-           lispobj copy;
-
-           /* must transport object -- object may point to either a
-            * function header, a closure function header, or to a
-            * closure header. */
-
-           type = TypeOf(first);
-           switch (type) {
-           case type_FunctionHeader:
-           case type_ClosureFunctionHeader:
-               copy = trans_function_header(object);
-               break;
-           default:
-               copy = trans_boxed(object);
-               break;
-           }
-
-           if (copy != object) {
-               /* Set forwarding pointer. */
-               first_pointer[0] = 0x01;
-               first_pointer[1] = copy;
-           }
-
-           first = copy;
-       }
-
-       gc_assert(Pointerp(first));
-       gc_assert(!from_space_p(first));
-
-       *where = first;
-    }
-    return 1;
-}
-#else
 static int
-scav_function_pointer(lispobj *where, lispobj object)
+scav_fun_pointer(lispobj *where, lispobj object)
 {
     lispobj *first_pointer;
     lispobj copy;
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
 
     /* Object is a pointer into from space - no a FP. */
-    first_pointer = (lispobj *) PTR(object);
+    first_pointer = (lispobj *) native_pointer(object);
 
     /* must transport object -- object may point to either a function
      * header, a closure function header, or to a closure header. */
 
-    switch (TypeOf(*first_pointer)) {
-    case type_FunctionHeader:
-    case type_ClosureFunctionHeader:
-       copy = trans_function_header(object);
+    switch (widetag_of(*first_pointer)) {
+    case SIMPLE_FUN_HEADER_WIDETAG:
+    case CLOSURE_FUN_HEADER_WIDETAG:
+       copy = trans_fun_header(object);
        break;
     default:
        copy = trans_boxed(object);
@@ -1890,14 +1829,13 @@ scav_function_pointer(lispobj *where, lispobj object)
        first_pointer[1] = copy;
     }
 
-    gc_assert(Pointerp(copy));
+    gc_assert(is_lisp_pointer(copy));
     gc_assert(!from_space_p(copy));
 
     *where = copy;
 
     return 1;
 }
-#endif
 
 /* Scan a x86 compiled code object, looking for possible fixups that
  * have been missed after a move.
@@ -1912,8 +1850,6 @@ void
 sniff_code_object(struct code *code, unsigned displacement)
 {
     int nheader_words, ncode_words, nwords;
-    lispobj fheaderl;
-    struct function *fheaderp;
     void *p;
     void *constants_start_addr, *constants_end_addr;
     void *code_start_addr, *code_end_addr;
@@ -1922,15 +1858,6 @@ sniff_code_object(struct code *code, unsigned displacement)
     if (!check_code_fixups)
        return;
 
-    /* It's ok if it's byte compiled code. The trace table offset will
-     * be a fixnum if it's x86 compiled code - check. */
-    if (code->trace_table_offset & 0x3) {
-       FSHOW((stderr, "/Sniffing byte compiled code object at %x.\n", code));
-       return;
-    }
-
-    /* Else it's x86 machine code. */
-
     ncode_words = fixnum_value(code->code_size);
     nheader_words = HeaderValue(*(lispobj *)code);
     nwords = ncode_words + nheader_words;
@@ -1947,8 +1874,10 @@ sniff_code_object(struct code *code, unsigned displacement)
        unsigned d2 = *((unsigned char *)p - 2);
        unsigned d3 = *((unsigned char *)p - 3);
        unsigned d4 = *((unsigned char *)p - 4);
+#if QSHOW
        unsigned d5 = *((unsigned char *)p - 5);
        unsigned d6 = *((unsigned char *)p - 6);
+#endif
 
        /* Check for code references. */
        /* Check for a 32 bit word that looks like an absolute
@@ -2093,19 +2022,10 @@ apply_code_fixups(struct code *old_code, struct code *new_code)
     int nheader_words, ncode_words, nwords;
     void *constants_start_addr, *constants_end_addr;
     void *code_start_addr, *code_end_addr;
-    lispobj p;
     lispobj fixups = NIL;
     unsigned displacement = (unsigned)new_code - (unsigned)old_code;
     struct vector *fixups_vector;
 
-    /* It's OK if it's byte compiled code. The trace table offset will
-     * be a fixnum if it's x86 compiled code - check. */
-    if (new_code->trace_table_offset & 0x3) {
-/*     FSHOW((stderr, "/byte compiled code object at %x\n", new_code)); */
-       return;
-    }
-
-    /* Else it's x86 machine code. */
     ncode_words = fixnum_value(new_code->code_size);
     nheader_words = HeaderValue(*(lispobj *)new_code);
     nwords = ncode_words + nheader_words;
@@ -2131,7 +2051,8 @@ apply_code_fixups(struct code *old_code, struct code *new_code)
 
     /* It will be 0 or the unbound-marker if there are no fixups, and
      * will be an other pointer if it is valid. */
-    if ((fixups == 0) || (fixups == type_UnboundMarker) || !Pointerp(fixups)) {
+    if ((fixups == 0) || (fixups == UNBOUND_MARKER_WIDETAG) ||
+       !is_lisp_pointer(fixups)) {
        /* Check for possible errors. */
        if (check_code_fixups)
            sniff_code_object(new_code, displacement);
@@ -2145,19 +2066,21 @@ apply_code_fixups(struct code *old_code, struct code *new_code)
        return;
     }
 
-    fixups_vector = (struct vector *)PTR(fixups);
+    fixups_vector = (struct vector *)native_pointer(fixups);
 
     /* Could be pointing to a forwarding pointer. */
-    if (Pointerp(fixups) && (find_page_index((void*)fixups_vector) != -1)
-       && (fixups_vector->header == 0x01)) {
+    if (is_lisp_pointer(fixups) &&
+       (find_page_index((void*)fixups_vector) != -1) &&
+       (fixups_vector->header == 0x01)) {
        /* If so, then follow it. */
        /*SHOW("following pointer to a forwarding pointer");*/
-       fixups_vector = (struct vector *)PTR((lispobj)fixups_vector->length);
+       fixups_vector = (struct vector *)native_pointer((lispobj)fixups_vector->length);
     }
 
     /*SHOW("got fixups");*/
 
-    if (TypeOf(fixups_vector->header) == type_SimpleArrayUnsignedByte32) {
+    if (widetag_of(fixups_vector->header) ==
+       SIMPLE_ARRAY_UNSIGNED_BYTE_32_WIDETAG) {
        /* Got the fixups for the code block. Now work through the vector,
           and apply a fixup at each address. */
        int length = fixnum_value(fixups_vector->length);
@@ -2207,10 +2130,10 @@ trans_code(struct code *code)
     if (*((lispobj *)code) == 0x01)
        return (struct code*)(((lispobj *)code)[1]);
 
-    gc_assert(TypeOf(code->header) == type_CodeHeader);
+    gc_assert(widetag_of(code->header) == CODE_HEADER_WIDETAG);
 
     /* Prepare to transport the code vector. */
-    l_code = (lispobj) code | type_OtherPointer;
+    l_code = (lispobj) code | OTHER_POINTER_LOWTAG;
 
     ncode_words = fixnum_value(code->code_size);
     nheader_words = HeaderValue(code->header);
@@ -2218,7 +2141,7 @@ trans_code(struct code *code)
     nwords = CEILING(nwords, 2);
 
     l_new_code = copy_large_object(l_code, nwords);
-    new_code = (struct code *) PTR(l_new_code);
+    new_code = (struct code *) native_pointer(l_new_code);
 
     /* may not have been moved.. */
     if (new_code == code)
@@ -2245,23 +2168,23 @@ trans_code(struct code *code)
     prev_pointer = &new_code->entry_points;
 
     while (fheaderl != NIL) {
-       struct function *fheaderp, *nfheaderp;
+       struct simple_fun *fheaderp, *nfheaderp;
        lispobj nfheaderl;
 
-       fheaderp = (struct function *) PTR(fheaderl);
-       gc_assert(TypeOf(fheaderp->header) == type_FunctionHeader);
+       fheaderp = (struct simple_fun *) native_pointer(fheaderl);
+       gc_assert(widetag_of(fheaderp->header) == SIMPLE_FUN_HEADER_WIDETAG);
 
        /* Calculate the new function pointer and the new */
        /* function header. */
        nfheaderl = fheaderl + displacement;
-       nfheaderp = (struct function *) PTR(nfheaderl);
+       nfheaderp = (struct simple_fun *) native_pointer(nfheaderl);
 
        /* Set forwarding pointer. */
        ((lispobj *)fheaderp)[0] = 0x01;
        ((lispobj *)fheaderp)[1] = nfheaderl;
 
        /* Fix self pointer. */
-       nfheaderp->self = nfheaderl + RAW_ADDR_OFFSET;
+       nfheaderp->self = nfheaderl + FUN_RAW_ADDR_OFFSET;
 
        *prev_pointer = nfheaderl;
 
@@ -2279,34 +2202,36 @@ static int
 scav_code_header(lispobj *where, lispobj object)
 {
     struct code *code;
-    int nheader_words, ncode_words, nwords;
-    lispobj fheaderl;
-    struct function *fheaderp;
+    int n_header_words, n_code_words, n_words;
+    lispobj entry_point;       /* tagged pointer to entry point */
+    struct simple_fun *function_ptr; /* untagged pointer to entry point */
 
     code = (struct code *) where;
-    ncode_words = fixnum_value(code->code_size);
-    nheader_words = HeaderValue(object);
-    nwords = ncode_words + nheader_words;
-    nwords = CEILING(nwords, 2);
+    n_code_words = fixnum_value(code->code_size);
+    n_header_words = HeaderValue(object);
+    n_words = n_code_words + n_header_words;
+    n_words = CEILING(n_words, 2);
 
     /* Scavenge the boxed section of the code data block. */
-    scavenge(where + 1, nheader_words - 1);
+    scavenge(where + 1, n_header_words - 1);
 
     /* Scavenge the boxed section of each function object in the */
     /* code data block. */
-    fheaderl = code->entry_points;
-    while (fheaderl != NIL) {
-       fheaderp = (struct function *) PTR(fheaderl);
-       gc_assert(TypeOf(fheaderp->header) == type_FunctionHeader);
+    for (entry_point = code->entry_points;
+        entry_point != NIL;
+        entry_point = function_ptr->next) {
 
-       scavenge(&fheaderp->name, 1);
-       scavenge(&fheaderp->arglist, 1);
-       scavenge(&fheaderp->type, 1);
-               
-       fheaderl = fheaderp->next;
+       gc_assert(is_lisp_pointer(entry_point));
+
+       function_ptr = (struct simple_fun *) native_pointer(entry_point);
+       gc_assert(widetag_of(function_ptr->header) == SIMPLE_FUN_HEADER_WIDETAG);
+
+       scavenge(&function_ptr->name, 1);
+       scavenge(&function_ptr->arglist, 1);
+       scavenge(&function_ptr->type, 1);
     }
        
-    return nwords;
+    return n_words;
 }
 
 static lispobj
@@ -2314,8 +2239,8 @@ trans_code_header(lispobj object)
 {
     struct code *ncode;
 
-    ncode = trans_code((struct code *) PTR(object));
-    return (lispobj) ncode | type_OtherPointer;
+    ncode = trans_code((struct code *) native_pointer(object));
+    return (lispobj) ncode | OTHER_POINTER_LOWTAG;
 }
 
 static int
@@ -2346,20 +2271,20 @@ scav_return_pc_header(lispobj *where, lispobj object)
 static lispobj
 trans_return_pc_header(lispobj object)
 {
-    struct function *return_pc;
+    struct simple_fun *return_pc;
     unsigned long offset;
     struct code *code, *ncode;
 
     SHOW("/trans_return_pc_header: Will this work?");
 
-    return_pc = (struct function *) PTR(object);
+    return_pc = (struct simple_fun *) native_pointer(object);
     offset = HeaderValue(return_pc->header) * 4;
 
     /* Transport the whole code object. */
     code = (struct code *) ((unsigned long) return_pc - offset);
     ncode = trans_code(code);
 
-    return ((lispobj) ncode + offset) | type_OtherPointer;
+    return ((lispobj) ncode + offset) | OTHER_POINTER_LOWTAG;
 }
 
 /* On the 386, closures hold a pointer to the raw address instead of the
@@ -2372,19 +2297,19 @@ scav_closure_header(lispobj *where, lispobj object)
     lispobj fun;
 
     closure = (struct closure *)where;
-    fun = closure->function - RAW_ADDR_OFFSET;
+    fun = closure->fun - FUN_RAW_ADDR_OFFSET;
     scavenge(&fun, 1);
     /* The function may have moved so update the raw address. But
      * don't write unnecessarily. */
-    if (closure->function != fun + RAW_ADDR_OFFSET)
-       closure->function = fun + RAW_ADDR_OFFSET;
+    if (closure->fun != fun + FUN_RAW_ADDR_OFFSET)
+       closure->fun = fun + FUN_RAW_ADDR_OFFSET;
 
     return 2;
 }
 #endif
 
 static int
-scav_function_header(lispobj *where, lispobj object)
+scav_fun_header(lispobj *where, lispobj object)
 {
     lose("attempted to scavenge a function header where=0x%08x object=0x%08x",
         (unsigned long) where,
@@ -2393,53 +2318,26 @@ scav_function_header(lispobj *where, lispobj object)
 }
 
 static lispobj
-trans_function_header(lispobj object)
+trans_fun_header(lispobj object)
 {
-    struct function *fheader;
+    struct simple_fun *fheader;
     unsigned long offset;
     struct code *code, *ncode;
 
-    fheader = (struct function *) PTR(object);
+    fheader = (struct simple_fun *) native_pointer(object);
     offset = HeaderValue(fheader->header) * 4;
 
     /* Transport the whole code object. */
     code = (struct code *) ((unsigned long) fheader - offset);
     ncode = trans_code(code);
 
-    return ((lispobj) ncode + offset) | type_FunctionPointer;
+    return ((lispobj) ncode + offset) | FUN_POINTER_LOWTAG;
 }
 \f
 /*
  * instances
  */
 
-#if DIRECT_SCAV
-static int
-scav_instance_pointer(lispobj *where, lispobj object)
-{
-    if (from_space_p(object)) {
-       lispobj first, *first_pointer;
-
-       /* Object is a pointer into from space. Check to see */
-       /* whether it has been forwarded. */
-       first_pointer = (lispobj *) PTR(object);
-       first = *first_pointer;
-
-       if (first == 0x01) {
-           /* forwarded */
-           first = first_pointer[1];
-       } else {
-           first = trans_boxed(object);
-           gc_assert(first != object);
-           /* Set forwarding pointer. */
-           first_pointer[0] = 0x01;
-           first_pointer[1] = first;
-       }
-       *where = first;
-    }
-    return 1;
-}
-#else
 static int
 scav_instance_pointer(lispobj *where, lispobj object)
 {
@@ -2450,7 +2348,7 @@ scav_instance_pointer(lispobj *where, lispobj object)
 
     gc_assert(copy != object);
 
-    first_pointer = (lispobj *) PTR(object);
+    first_pointer = (lispobj *) native_pointer(object);
 
     /* Set forwarding pointer. */
     first_pointer[0] = 0x01;
@@ -2459,7 +2357,6 @@ scav_instance_pointer(lispobj *where, lispobj object)
 
     return 1;
 }
-#endif
 \f
 /*
  * lists and conses
@@ -2467,84 +2364,46 @@ scav_instance_pointer(lispobj *where, lispobj object)
 
 static lispobj trans_list(lispobj object);
 
-#if DIRECT_SCAV
-static int
-scav_list_pointer(lispobj *where, lispobj object)
-{
-    /* KLUDGE: There's lots of cut-and-paste duplication between this
-     * and scav_instance_pointer(..), scav_other_pointer(..), and
-     * perhaps other functions too. -- WHN 20000620 */
-
-    gc_assert(Pointerp(object));
-
-    if (from_space_p(object)) {
-       lispobj first, *first_pointer;
-
-       /* Object is a pointer into from space. Check to see whether it has
-        * been forwarded. */
-       first_pointer = (lispobj *) PTR(object);
-       first = *first_pointer;
-
-       if (first == 0x01) {
-           /* forwarded */
-           first = first_pointer[1];
-       } else {
-           first = trans_list(object);
-
-           /* Set forwarding pointer */
-           first_pointer[0] = 0x01;
-           first_pointer[1] = first;
-       }
-
-       gc_assert(Pointerp(first));
-       gc_assert(!from_space_p(first));
-       *where = first;
-    }
-    return 1;
-}
-#else
 static int
 scav_list_pointer(lispobj *where, lispobj object)
 {
     lispobj first, *first_pointer;
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
 
     /* Object is a pointer into from space - not FP. */
 
     first = trans_list(object);
     gc_assert(first != object);
 
-    first_pointer = (lispobj *) PTR(object);
+    first_pointer = (lispobj *) native_pointer(object);
 
     /* Set forwarding pointer */
     first_pointer[0] = 0x01;
     first_pointer[1] = first;
 
-    gc_assert(Pointerp(first));
+    gc_assert(is_lisp_pointer(first));
     gc_assert(!from_space_p(first));
     *where = first;
     return 1;
 }
-#endif
 
 static lispobj
 trans_list(lispobj object)
 {
     lispobj new_list_pointer;
     struct cons *cons, *new_cons;
-    int n = 0;
     lispobj cdr;
 
     gc_assert(from_space_p(object));
 
-    cons = (struct cons *) PTR(object);
+    cons = (struct cons *) native_pointer(object);
 
     /* Copy 'object'. */
     new_cons = (struct cons *) gc_quick_alloc(sizeof(struct cons));
     new_cons->car = cons->car;
     new_cons->cdr = cons->cdr; /* updated later */
-    new_list_pointer = (lispobj)new_cons | LowtagOf(object);
+    new_list_pointer = (lispobj)new_cons | lowtag_of(object);
 
     /* Grab the cdr before it is clobbered. */
     cdr = cons->cdr;
@@ -2559,17 +2418,17 @@ trans_list(lispobj object)
        lispobj  new_cdr;
        struct cons *cdr_cons, *new_cdr_cons;
 
-       if (LowtagOf(cdr) != type_ListPointer || !from_space_p(cdr)
-           || (*((lispobj *)PTR(cdr)) == 0x01))
+       if (lowtag_of(cdr) != LIST_POINTER_LOWTAG || !from_space_p(cdr)
+           || (*((lispobj *)native_pointer(cdr)) == 0x01))
            break;
 
-       cdr_cons = (struct cons *) PTR(cdr);
+       cdr_cons = (struct cons *) native_pointer(cdr);
 
        /* Copy 'cdr'. */
        new_cdr_cons = (struct cons*) gc_quick_alloc(sizeof(struct cons));
        new_cdr_cons->car = cdr_cons->car;
        new_cdr_cons->cdr = cdr_cons->cdr;
-       new_cdr = (lispobj)new_cdr_cons | LowtagOf(cdr);
+       new_cdr = (lispobj)new_cdr_cons | lowtag_of(cdr);
 
        /* Grab the cdr before it is clobbered. */
        cdr = cdr_cons->cdr;
@@ -2593,52 +2452,17 @@ trans_list(lispobj object)
  * scavenging and transporting other pointers
  */
 
-#if DIRECT_SCAV
-static int
-scav_other_pointer(lispobj *where, lispobj object)
-{
-    gc_assert(Pointerp(object));
-
-    if (from_space_p(object)) {
-       lispobj first, *first_pointer;
-
-       /* Object is a pointer into from space. Check to see */
-       /* whether it has been forwarded. */
-       first_pointer = (lispobj *) PTR(object);
-       first = *first_pointer;
-
-       if (first == 0x01) {
-           /* Forwarded. */
-           first = first_pointer[1];
-           *where = first;
-       } else {
-           first = (transother[TypeOf(first)])(object);
-
-           if (first != object) {
-               /* Set forwarding pointer */
-               first_pointer[0] = 0x01;
-               first_pointer[1] = first;
-               *where = first;
-           }
-       }
-
-       gc_assert(Pointerp(first));
-       gc_assert(!from_space_p(first));
-    }
-    return 1;
-}
-#else
 static int
 scav_other_pointer(lispobj *where, lispobj object)
 {
     lispobj first, *first_pointer;
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
 
     /* Object is a pointer into from space - not FP. */
-    first_pointer = (lispobj *) PTR(object);
+    first_pointer = (lispobj *) native_pointer(object);
 
-    first = (transother[TypeOf(*first_pointer)])(object);
+    first = (transother[widetag_of(*first_pointer)])(object);
 
     if (first != object) {
        /* Set forwarding pointer. */
@@ -2647,13 +2471,11 @@ scav_other_pointer(lispobj *where, lispobj object)
        *where = first;
     }
 
-    gc_assert(Pointerp(first));
+    gc_assert(is_lisp_pointer(first));
     gc_assert(!from_space_p(first));
 
     return 1;
 }
-#endif
-
 \f
 /*
  * immediate, boxed, and unboxed objects
@@ -2697,9 +2519,9 @@ trans_boxed(lispobj object)
     lispobj header;
     unsigned long length;
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
 
-    header = *((lispobj *) PTR(object));
+    header = *((lispobj *) native_pointer(object));
     length = HeaderValue(header) + 1;
     length = CEILING(length, 2);
 
@@ -2712,9 +2534,9 @@ trans_boxed_large(lispobj object)
     lispobj header;
     unsigned long length;
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
 
-    header = *((lispobj *) PTR(object));
+    header = *((lispobj *) native_pointer(object));
     length = HeaderValue(header) + 1;
     length = CEILING(length, 2);
 
@@ -2742,14 +2564,14 @@ scav_fdefn(lispobj *where, lispobj object)
     fdefn = (struct fdefn *)where;
 
     /* FSHOW((stderr, "scav_fdefn, function = %p, raw_addr = %p\n", 
-       fdefn->function, fdefn->raw_addr)); */
+       fdefn->fun, fdefn->raw_addr)); */
 
-    if ((char *)(fdefn->function + RAW_ADDR_OFFSET) == fdefn->raw_addr) {
+    if ((char *)(fdefn->fun + FUN_RAW_ADDR_OFFSET) == fdefn->raw_addr) {
        scavenge(where + 1, sizeof(struct fdefn)/sizeof(lispobj) - 1);
 
        /* Don't write unnecessarily. */
-       if (fdefn->raw_addr != (char *)(fdefn->function + RAW_ADDR_OFFSET))
-           fdefn->raw_addr = (char *)(fdefn->function + RAW_ADDR_OFFSET);
+       if (fdefn->raw_addr != (char *)(fdefn->fun + FUN_RAW_ADDR_OFFSET))
+           fdefn->raw_addr = (char *)(fdefn->fun + FUN_RAW_ADDR_OFFSET);
 
        return sizeof(struct fdefn) / sizeof(lispobj);
     } else {
@@ -2775,9 +2597,9 @@ trans_unboxed(lispobj object)
     unsigned long length;
 
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
 
-    header = *((lispobj *) PTR(object));
+    header = *((lispobj *) native_pointer(object));
     length = HeaderValue(header) + 1;
     length = CEILING(length, 2);
 
@@ -2791,9 +2613,9 @@ trans_unboxed_large(lispobj object)
     unsigned long length;
 
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
 
-    header = *((lispobj *) PTR(object));
+    header = *((lispobj *) native_pointer(object));
     length = HeaderValue(header) + 1;
     length = CEILING(length, 2);
 
@@ -2841,13 +2663,13 @@ trans_string(lispobj object)
     struct vector *vector;
     int length, nwords;
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
 
     /* NOTE: A string contains one more byte of data (a terminating
      * '\0' to help when interfacing with C functions) than indicated
      * by the length slot. */
 
-    vector = (struct vector *) PTR(object);
+    vector = (struct vector *) native_pointer(object);
     length = fixnum_value(vector->length) + 1;
     nwords = CEILING(NWORDS(length, 4) + 2, 2);
 
@@ -2879,12 +2701,14 @@ scav_vector(lispobj *where, lispobj object)
 {
     unsigned int kv_length;
     lispobj *kv_vector;
-    unsigned int  length;
+    unsigned int length = 0; /* (0 = dummy to stop GCC warning) */
     lispobj *hash_table;
     lispobj empty_symbol;
-    unsigned int  *index_vector, *next_vector, *hash_vector;
+    unsigned int *index_vector = NULL; /* (NULL = dummy to stop GCC warning) */
+    unsigned int *next_vector = NULL; /* (NULL = dummy to stop GCC warning) */
+    unsigned int *hash_vector = NULL; /* (NULL = dummy to stop GCC warning) */
     lispobj weak_p_obj;
-    unsigned next_vector_length;
+    unsigned next_vector_length = 0;
 
     /* FIXME: A comment explaining this would be nice. It looks as
      * though SB-VM:VECTOR-VALID-HASHING-SUBTYPE is set for EQ-based
@@ -2895,7 +2719,8 @@ scav_vector(lispobj *where, lispobj object)
     if (!gencgc_hash) {
        /* This is set for backward compatibility. FIXME: Do we need
         * this any more? */
-       *where = (subtype_VectorMustRehash << type_Bits) | type_SimpleVector;
+       *where =
+           (subtype_VectorMustRehash<<N_WIDETAG_BITS) | SIMPLE_VECTOR_WIDETAG;
        return 1;
     }
 
@@ -2905,26 +2730,27 @@ scav_vector(lispobj *where, lispobj object)
 
     /* Scavenge element 0, which may be a hash-table structure. */
     scavenge(where+2, 1);
-    if (!Pointerp(where[2])) {
+    if (!is_lisp_pointer(where[2])) {
        lose("no pointer at %x in hash table", where[2]);
     }
-    hash_table = (lispobj *)PTR(where[2]);
+    hash_table = (lispobj *)native_pointer(where[2]);
     /*FSHOW((stderr,"/hash_table = %x\n", hash_table));*/
-    if (TypeOf(hash_table[0]) != type_InstanceHeader) {
+    if (widetag_of(hash_table[0]) != INSTANCE_HEADER_WIDETAG) {
        lose("hash table not instance (%x at %x)", hash_table[0], hash_table);
     }
 
     /* Scavenge element 1, which should be some internal symbol that
      * the hash table code reserves for marking empty slots. */
     scavenge(where+3, 1);
-    if (!Pointerp(where[3])) {
-       lose("not #:%EMPTY-HT-SLOT% symbol pointer: %x", where[3]);
+    if (!is_lisp_pointer(where[3])) {
+       lose("not empty-hash-table-slot symbol pointer: %x", where[3]);
     }
     empty_symbol = where[3];
     /* fprintf(stderr,"* empty_symbol = %x\n", empty_symbol);*/
-    if (TypeOf(*(lispobj *)PTR(empty_symbol)) != type_SymbolHeader) {
-       lose("not a symbol where #:%EMPTY-HT-SLOT% expected: %x",
-            *(lispobj *)PTR(empty_symbol));
+    if (widetag_of(*(lispobj *)native_pointer(empty_symbol)) !=
+       SYMBOL_HEADER_WIDETAG) {
+       lose("not a symbol where empty-hash-table-slot symbol expected: %x",
+            *(lispobj *)native_pointer(empty_symbol));
     }
 
     /* Scavenge hash table, which will fix the positions of the other
@@ -2932,7 +2758,7 @@ scav_vector(lispobj *where, lispobj object)
     scavenge(hash_table, 16);
 
     /* Cross-check the kv_vector. */
-    if (where != (lispobj *)PTR(hash_table[9])) {
+    if (where != (lispobj *)native_pointer(hash_table[9])) {
        lose("hash_table table!=this table %x", hash_table[9]);
     }
 
@@ -2943,11 +2769,12 @@ scav_vector(lispobj *where, lispobj object)
     {
        lispobj index_vector_obj = hash_table[13];
 
-       if (Pointerp(index_vector_obj) &&
-           (TypeOf(*(lispobj *)PTR(index_vector_obj)) == type_SimpleArrayUnsignedByte32)) {
-           index_vector = ((unsigned int *)PTR(index_vector_obj)) + 2;
+       if (is_lisp_pointer(index_vector_obj) &&
+           (widetag_of(*(lispobj *)native_pointer(index_vector_obj)) ==
+            SIMPLE_ARRAY_UNSIGNED_BYTE_32_WIDETAG)) {
+           index_vector = ((unsigned int *)native_pointer(index_vector_obj)) + 2;
            /*FSHOW((stderr, "/index_vector = %x\n",index_vector));*/
-           length = fixnum_value(((unsigned int *)PTR(index_vector_obj))[1]);
+           length = fixnum_value(((unsigned int *)native_pointer(index_vector_obj))[1]);
            /*FSHOW((stderr, "/length = %d\n", length));*/
        } else {
            lose("invalid index_vector %x", index_vector_obj);
@@ -2958,11 +2785,12 @@ scav_vector(lispobj *where, lispobj object)
     {
        lispobj next_vector_obj = hash_table[14];
 
-       if (Pointerp(next_vector_obj) &&
-           (TypeOf(*(lispobj *)PTR(next_vector_obj)) == type_SimpleArrayUnsignedByte32)) {
-           next_vector = ((unsigned int *)PTR(next_vector_obj)) + 2;
+       if (is_lisp_pointer(next_vector_obj) &&
+           (widetag_of(*(lispobj *)native_pointer(next_vector_obj)) ==
+            SIMPLE_ARRAY_UNSIGNED_BYTE_32_WIDETAG)) {
+           next_vector = ((unsigned int *)native_pointer(next_vector_obj)) + 2;
            /*FSHOW((stderr, "/next_vector = %x\n", next_vector));*/
-           next_vector_length = fixnum_value(((unsigned int *)PTR(next_vector_obj))[1]);
+           next_vector_length = fixnum_value(((unsigned int *)native_pointer(next_vector_obj))[1]);
            /*FSHOW((stderr, "/next_vector_length = %d\n", next_vector_length));*/
        } else {
            lose("invalid next_vector %x", next_vector_obj);
@@ -2977,12 +2805,12 @@ scav_vector(lispobj *where, lispobj object)
         * probably other stuff too. Ugh.. */
        lispobj hash_vector_obj = hash_table[15];
 
-       if (Pointerp(hash_vector_obj) &&
-           (TypeOf(*(lispobj *)PTR(hash_vector_obj))
-            == type_SimpleArrayUnsignedByte32)) {
-           hash_vector = ((unsigned int *)PTR(hash_vector_obj)) + 2;
+       if (is_lisp_pointer(hash_vector_obj) &&
+           (widetag_of(*(lispobj *)native_pointer(hash_vector_obj))
+            == SIMPLE_ARRAY_UNSIGNED_BYTE_32_WIDETAG)) {
+           hash_vector = ((unsigned int *)native_pointer(hash_vector_obj)) + 2;
            /*FSHOW((stderr, "/hash_vector = %x\n", hash_vector));*/
-           gc_assert(fixnum_value(((unsigned int *)PTR(hash_vector_obj))[1])
+           gc_assert(fixnum_value(((unsigned int *)native_pointer(hash_vector_obj))[1])
                      == next_vector_length);
        } else {
            hash_vector = NULL;
@@ -3069,9 +2897,9 @@ trans_vector(lispobj object)
     struct vector *vector;
     int length, nwords;
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
 
-    vector = (struct vector *) PTR(object);
+    vector = (struct vector *) native_pointer(object);
 
     length = fixnum_value(vector->length);
     nwords = CEILING(length + 2, 2);
@@ -3112,9 +2940,9 @@ trans_vector_bit(lispobj object)
     struct vector *vector;
     int length, nwords;
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
 
-    vector = (struct vector *) PTR(object);
+    vector = (struct vector *) native_pointer(object);
     length = fixnum_value(vector->length);
     nwords = CEILING(NWORDS(length, 32) + 2, 2);
 
@@ -3154,9 +2982,9 @@ trans_vector_unsigned_byte_2(lispobj object)
     struct vector *vector;
     int length, nwords;
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
 
-    vector = (struct vector *) PTR(object);
+    vector = (struct vector *) native_pointer(object);
     length = fixnum_value(vector->length);
     nwords = CEILING(NWORDS(length, 16) + 2, 2);
 
@@ -3196,9 +3024,9 @@ trans_vector_unsigned_byte_4(lispobj object)
     struct vector *vector;
     int length, nwords;
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
 
-    vector = (struct vector *) PTR(object);
+    vector = (struct vector *) native_pointer(object);
     length = fixnum_value(vector->length);
     nwords = CEILING(NWORDS(length, 8) + 2, 2);
 
@@ -3237,9 +3065,9 @@ trans_vector_unsigned_byte_8(lispobj object)
     struct vector *vector;
     int length, nwords;
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
 
-    vector = (struct vector *) PTR(object);
+    vector = (struct vector *) native_pointer(object);
     length = fixnum_value(vector->length);
     nwords = CEILING(NWORDS(length, 4) + 2, 2);
 
@@ -3279,9 +3107,9 @@ trans_vector_unsigned_byte_16(lispobj object)
     struct vector *vector;
     int length, nwords;
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
 
-    vector = (struct vector *) PTR(object);
+    vector = (struct vector *) native_pointer(object);
     length = fixnum_value(vector->length);
     nwords = CEILING(NWORDS(length, 2) + 2, 2);
 
@@ -3320,9 +3148,9 @@ trans_vector_unsigned_byte_32(lispobj object)
     struct vector *vector;
     int length, nwords;
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
 
-    vector = (struct vector *) PTR(object);
+    vector = (struct vector *) native_pointer(object);
     length = fixnum_value(vector->length);
     nwords = CEILING(length + 2, 2);
 
@@ -3361,9 +3189,9 @@ trans_vector_single_float(lispobj object)
     struct vector *vector;
     int length, nwords;
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
 
-    vector = (struct vector *) PTR(object);
+    vector = (struct vector *) native_pointer(object);
     length = fixnum_value(vector->length);
     nwords = CEILING(length + 2, 2);
 
@@ -3402,9 +3230,9 @@ trans_vector_double_float(lispobj object)
     struct vector *vector;
     int length, nwords;
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
 
-    vector = (struct vector *) PTR(object);
+    vector = (struct vector *) native_pointer(object);
     length = fixnum_value(vector->length);
     nwords = CEILING(length * 2 + 2, 2);
 
@@ -3424,7 +3252,7 @@ size_vector_double_float(lispobj *where)
     return nwords;
 }
 
-#ifdef type_SimpleArrayLongFloat
+#ifdef SIMPLE_ARRAY_LONG_FLOAT_WIDETAG
 static int
 scav_vector_long_float(lispobj *where, lispobj object)
 {
@@ -3444,9 +3272,9 @@ trans_vector_long_float(lispobj object)
     struct vector *vector;
     int length, nwords;
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
 
-    vector = (struct vector *) PTR(object);
+    vector = (struct vector *) native_pointer(object);
     length = fixnum_value(vector->length);
     nwords = CEILING(length * 3 + 2, 2);
 
@@ -3468,7 +3296,7 @@ size_vector_long_float(lispobj *where)
 #endif
 
 
-#ifdef type_SimpleArrayComplexSingleFloat
+#ifdef SIMPLE_ARRAY_COMPLEX_SINGLE_FLOAT_WIDETAG
 static int
 scav_vector_complex_single_float(lispobj *where, lispobj object)
 {
@@ -3488,9 +3316,9 @@ trans_vector_complex_single_float(lispobj object)
     struct vector *vector;
     int length, nwords;
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
 
-    vector = (struct vector *) PTR(object);
+    vector = (struct vector *) native_pointer(object);
     length = fixnum_value(vector->length);
     nwords = CEILING(length * 2 + 2, 2);
 
@@ -3511,7 +3339,7 @@ size_vector_complex_single_float(lispobj *where)
 }
 #endif
 
-#ifdef type_SimpleArrayComplexDoubleFloat
+#ifdef SIMPLE_ARRAY_COMPLEX_DOUBLE_FLOAT_WIDETAG
 static int
 scav_vector_complex_double_float(lispobj *where, lispobj object)
 {
@@ -3531,9 +3359,9 @@ trans_vector_complex_double_float(lispobj object)
     struct vector *vector;
     int length, nwords;
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
 
-    vector = (struct vector *) PTR(object);
+    vector = (struct vector *) native_pointer(object);
     length = fixnum_value(vector->length);
     nwords = CEILING(length * 4 + 2, 2);
 
@@ -3555,7 +3383,7 @@ size_vector_complex_double_float(lispobj *where)
 #endif
 
 
-#ifdef type_SimpleArrayComplexLongFloat
+#ifdef SIMPLE_ARRAY_COMPLEX_LONG_FLOAT_WIDETAG
 static int
 scav_vector_complex_long_float(lispobj *where, lispobj object)
 {
@@ -3575,9 +3403,9 @@ trans_vector_complex_long_float(lispobj object)
     struct vector *vector;
     int length, nwords;
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
 
-    vector = (struct vector *) PTR(object);
+    vector = (struct vector *) native_pointer(object);
     length = fixnum_value(vector->length);
     nwords = CEILING(length * 6 + 2, 2);
 
@@ -3649,9 +3477,9 @@ static lispobj
 trans_weak_pointer(lispobj object)
 {
     lispobj copy;
-    struct weak_pointer *wp;
+    /* struct weak_pointer *wp; */
 
-    gc_assert(Pointerp(object));
+    gc_assert(is_lisp_pointer(object));
 
 #if defined(DEBUG_WEAK)
     FSHOW((stderr, "Transporting weak pointer from 0x%08x\n", object));
@@ -3661,7 +3489,7 @@ trans_weak_pointer(lispobj object)
     /* been transported so they can be fixed up in a post-GC pass. */
 
     copy = copy_object(object, WEAK_POINTER_NWORDS);
-    /*  wp = (struct weak_pointer *) PTR(copy);*/
+    /*  wp = (struct weak_pointer *) native_pointer(copy);*/
        
 
     /* Push the weak pointer onto the list of weak pointers. */
@@ -3682,16 +3510,11 @@ void scan_weak_pointers(void)
     struct weak_pointer *wp;
     for (wp = weak_pointers; wp != NULL; wp = wp->next) {
        lispobj value = wp->value;
-       lispobj first, *first_pointer;
-
-       first_pointer = (lispobj *)PTR(value);
+       lispobj *first_pointer;
 
-       /*
-       FSHOW((stderr, "/weak pointer at 0x%08x\n", (unsigned long) wp));
-       FSHOW((stderr, "/value: 0x%08x\n", (unsigned long) value));
-       */
+       first_pointer = (lispobj *)native_pointer(value);
 
-       if (Pointerp(value) && from_space_p(value)) {
+       if (is_lisp_pointer(value) && from_space_p(value)) {
            /* Now, we need to check whether the object has been forwarded. If
             * it has been, the weak pointer is still good and needs to be
             * updated. Otherwise, the weak pointer needs to be nil'ed
@@ -3700,7 +3523,6 @@ void scan_weak_pointers(void)
                wp->value = first_pointer[1];
            } else {
                /* Break it. */
-               SHOW("broken");
                wp->value = NIL;
                wp->broken = T;
            }
@@ -3715,21 +3537,27 @@ void scan_weak_pointers(void)
 static int
 scav_lose(lispobj *where, lispobj object)
 {
-    lose("no scavenge function for object 0x%08x", (unsigned long) object);
+    lose("no scavenge function for object 0x%08x (widetag 0x%x)",
+        (unsigned long)object,
+        widetag_of(*(lispobj*)native_pointer(object)));
     return 0; /* bogus return value to satisfy static type checking */
 }
 
 static lispobj
 trans_lose(lispobj object)
 {
-    lose("no transport function for object 0x%08x", (unsigned long) object);
+    lose("no transport function for object 0x%08x (widetag 0x%x)",
+        (unsigned long)object,
+        widetag_of(*(lispobj*)native_pointer(object)));
     return NIL; /* bogus return value to satisfy static type checking */
 }
 
 static int
 size_lose(lispobj *where)
 {
-    lose("no size function for object at 0x%08x", (unsigned long) where);
+    lose("no size function for object at 0x%08x (widetag 0x%x)",
+        (unsigned long)where,
+        widetag_of(where));
     return 1; /* bogus return value to satisfy static type checking */
 }
 
@@ -3743,264 +3571,297 @@ gc_init_tables(void)
        scavtab[i] = scav_lose;
     }
 
-    /* For each type which can be selected by the low 3 bits of the tag
-     * alone, set multiple entries in our 8-bit scavenge table (one for each
-     * possible value of the high 5 bits). */
-    for (i = 0; i < 32; i++) { /* FIXME: bare constant length, ick! */
-       scavtab[type_EvenFixnum|(i<<3)] = scav_immediate;
-       scavtab[type_FunctionPointer|(i<<3)] = scav_function_pointer;
-       /* OtherImmediate0 */
-       scavtab[type_ListPointer|(i<<3)] = scav_list_pointer;
-       scavtab[type_OddFixnum|(i<<3)] = scav_immediate;
-       scavtab[type_InstancePointer|(i<<3)] = scav_instance_pointer;
-       /* OtherImmediate1 */
-       scavtab[type_OtherPointer|(i<<3)] = scav_other_pointer;
+    /* For each type which can be selected by the lowtag alone, set
+     * multiple entries in our widetag scavenge table (one for each
+     * possible value of the high bits).
+     *
+     * FIXME: bare constant 32 and 3 here, ick! */
+    for (i = 0; i < 32; i++) {
+       scavtab[EVEN_FIXNUM_LOWTAG|(i<<3)] = scav_immediate;
+       scavtab[FUN_POINTER_LOWTAG|(i<<3)] = scav_fun_pointer;
+       /* skipping OTHER_IMMEDIATE_0_LOWTAG */
+       scavtab[LIST_POINTER_LOWTAG|(i<<3)] = scav_list_pointer;
+       scavtab[ODD_FIXNUM_LOWTAG|(i<<3)] = scav_immediate;
+       scavtab[INSTANCE_POINTER_LOWTAG|(i<<3)] = scav_instance_pointer;
+       /* skipping OTHER_IMMEDIATE_1_LOWTAG */
+       scavtab[OTHER_POINTER_LOWTAG|(i<<3)] = scav_other_pointer;
     }
 
-    /* Other-pointer types (those selected by all eight bits of the tag) get
-     * one entry each in the scavenge table. */
-    scavtab[type_Bignum] = scav_unboxed;
-    scavtab[type_Ratio] = scav_boxed;
-    scavtab[type_SingleFloat] = scav_unboxed;
-    scavtab[type_DoubleFloat] = scav_unboxed;
-#ifdef type_LongFloat
-    scavtab[type_LongFloat] = scav_unboxed;
+    /* Other-pointer types (those selected by all eight bits of the
+     * tag) get one entry each in the scavenge table. */
+    scavtab[BIGNUM_WIDETAG] = scav_unboxed;
+    scavtab[RATIO_WIDETAG] = scav_boxed;
+    scavtab[SINGLE_FLOAT_WIDETAG] = scav_unboxed;
+    scavtab[DOUBLE_FLOAT_WIDETAG] = scav_unboxed;
+#ifdef LONG_FLOAT_WIDETAG
+    scavtab[LONG_FLOAT_WIDETAG] = scav_unboxed;
 #endif
-    scavtab[type_Complex] = scav_boxed;
-#ifdef type_ComplexSingleFloat
-    scavtab[type_ComplexSingleFloat] = scav_unboxed;
+    scavtab[COMPLEX_WIDETAG] = scav_boxed;
+#ifdef COMPLEX_SINGLE_FLOAT_WIDETAG
+    scavtab[COMPLEX_SINGLE_FLOAT_WIDETAG] = scav_unboxed;
 #endif
-#ifdef type_ComplexDoubleFloat
-    scavtab[type_ComplexDoubleFloat] = scav_unboxed;
+#ifdef COMPLEX_DOUBLE_FLOAT_WIDETAG
+    scavtab[COMPLEX_DOUBLE_FLOAT_WIDETAG] = scav_unboxed;
 #endif
-#ifdef type_ComplexLongFloat
-    scavtab[type_ComplexLongFloat] = scav_unboxed;
+#ifdef COMPLEX_LONG_FLOAT_WIDETAG
+    scavtab[COMPLEX_LONG_FLOAT_WIDETAG] = scav_unboxed;
 #endif
-    scavtab[type_SimpleArray] = scav_boxed;
-    scavtab[type_SimpleString] = scav_string;
-    scavtab[type_SimpleBitVector] = scav_vector_bit;
-    scavtab[type_SimpleVector] = scav_vector;
-    scavtab[type_SimpleArrayUnsignedByte2] = scav_vector_unsigned_byte_2;
-    scavtab[type_SimpleArrayUnsignedByte4] = scav_vector_unsigned_byte_4;
-    scavtab[type_SimpleArrayUnsignedByte8] = scav_vector_unsigned_byte_8;
-    scavtab[type_SimpleArrayUnsignedByte16] = scav_vector_unsigned_byte_16;
-    scavtab[type_SimpleArrayUnsignedByte32] = scav_vector_unsigned_byte_32;
-#ifdef type_SimpleArraySignedByte8
-    scavtab[type_SimpleArraySignedByte8] = scav_vector_unsigned_byte_8;
+    scavtab[SIMPLE_ARRAY_WIDETAG] = scav_boxed;
+    scavtab[SIMPLE_STRING_WIDETAG] = scav_string;
+    scavtab[SIMPLE_BIT_VECTOR_WIDETAG] = scav_vector_bit;
+    scavtab[SIMPLE_VECTOR_WIDETAG] = scav_vector;
+    scavtab[SIMPLE_ARRAY_UNSIGNED_BYTE_2_WIDETAG] =
+       scav_vector_unsigned_byte_2;
+    scavtab[SIMPLE_ARRAY_UNSIGNED_BYTE_4_WIDETAG] =
+       scav_vector_unsigned_byte_4;
+    scavtab[SIMPLE_ARRAY_UNSIGNED_BYTE_8_WIDETAG] =
+       scav_vector_unsigned_byte_8;
+    scavtab[SIMPLE_ARRAY_UNSIGNED_BYTE_16_WIDETAG] =
+       scav_vector_unsigned_byte_16;
+    scavtab[SIMPLE_ARRAY_UNSIGNED_BYTE_32_WIDETAG] =
+       scav_vector_unsigned_byte_32;
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_8_WIDETAG
+    scavtab[SIMPLE_ARRAY_SIGNED_BYTE_8_WIDETAG] = scav_vector_unsigned_byte_8;
 #endif
-#ifdef type_SimpleArraySignedByte16
-    scavtab[type_SimpleArraySignedByte16] = scav_vector_unsigned_byte_16;
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_16_WIDETAG
+    scavtab[SIMPLE_ARRAY_SIGNED_BYTE_16_WIDETAG] =
+       scav_vector_unsigned_byte_16;
 #endif
-#ifdef type_SimpleArraySignedByte30
-    scavtab[type_SimpleArraySignedByte30] = scav_vector_unsigned_byte_32;
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_30_WIDETAG
+    scavtab[SIMPLE_ARRAY_SIGNED_BYTE_30_WIDETAG] =
+       scav_vector_unsigned_byte_32;
 #endif
-#ifdef type_SimpleArraySignedByte32
-    scavtab[type_SimpleArraySignedByte32] = scav_vector_unsigned_byte_32;
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_32_WIDETAG
+    scavtab[SIMPLE_ARRAY_SIGNED_BYTE_32_WIDETAG] =
+       scav_vector_unsigned_byte_32;
 #endif
-    scavtab[type_SimpleArraySingleFloat] = scav_vector_single_float;
-    scavtab[type_SimpleArrayDoubleFloat] = scav_vector_double_float;
-#ifdef type_SimpleArrayLongFloat
-    scavtab[type_SimpleArrayLongFloat] = scav_vector_long_float;
+    scavtab[SIMPLE_ARRAY_SINGLE_FLOAT_WIDETAG] = scav_vector_single_float;
+    scavtab[SIMPLE_ARRAY_DOUBLE_FLOAT_WIDETAG] = scav_vector_double_float;
+#ifdef SIMPLE_ARRAY_LONG_FLOAT_WIDETAG
+    scavtab[SIMPLE_ARRAY_LONG_FLOAT_WIDETAG] = scav_vector_long_float;
 #endif
-#ifdef type_SimpleArrayComplexSingleFloat
-    scavtab[type_SimpleArrayComplexSingleFloat] = scav_vector_complex_single_float;
+#ifdef SIMPLE_ARRAY_COMPLEX_SINGLE_FLOAT_WIDETAG
+    scavtab[SIMPLE_ARRAY_COMPLEX_SINGLE_FLOAT_WIDETAG] =
+       scav_vector_complex_single_float;
 #endif
-#ifdef type_SimpleArrayComplexDoubleFloat
-    scavtab[type_SimpleArrayComplexDoubleFloat] = scav_vector_complex_double_float;
+#ifdef SIMPLE_ARRAY_COMPLEX_DOUBLE_FLOAT_WIDETAG
+    scavtab[SIMPLE_ARRAY_COMPLEX_DOUBLE_FLOAT_WIDETAG] =
+       scav_vector_complex_double_float;
 #endif
-#ifdef type_SimpleArrayComplexLongFloat
-    scavtab[type_SimpleArrayComplexLongFloat] = scav_vector_complex_long_float;
+#ifdef SIMPLE_ARRAY_COMPLEX_LONG_FLOAT_WIDETAG
+    scavtab[SIMPLE_ARRAY_COMPLEX_LONG_FLOAT_WIDETAG] =
+       scav_vector_complex_long_float;
 #endif
-    scavtab[type_ComplexString] = scav_boxed;
-    scavtab[type_ComplexBitVector] = scav_boxed;
-    scavtab[type_ComplexVector] = scav_boxed;
-    scavtab[type_ComplexArray] = scav_boxed;
-    scavtab[type_CodeHeader] = scav_code_header;
-    /*scavtab[type_FunctionHeader] = scav_function_header;*/
-    /*scavtab[type_ClosureFunctionHeader] = scav_function_header;*/
-    /*scavtab[type_ReturnPcHeader] = scav_return_pc_header;*/
+    scavtab[COMPLEX_STRING_WIDETAG] = scav_boxed;
+    scavtab[COMPLEX_BIT_VECTOR_WIDETAG] = scav_boxed;
+    scavtab[COMPLEX_VECTOR_WIDETAG] = scav_boxed;
+    scavtab[COMPLEX_ARRAY_WIDETAG] = scav_boxed;
+    scavtab[CODE_HEADER_WIDETAG] = scav_code_header;
+    /*scavtab[SIMPLE_FUN_HEADER_WIDETAG] = scav_fun_header;*/
+    /*scavtab[CLOSURE_FUN_HEADER_WIDETAG] = scav_fun_header;*/
+    /*scavtab[RETURN_PC_HEADER_WIDETAG] = scav_return_pc_header;*/
 #ifdef __i386__
-    scavtab[type_ClosureHeader] = scav_closure_header;
-    scavtab[type_FuncallableInstanceHeader] = scav_closure_header;
-    scavtab[type_ByteCodeFunction] = scav_closure_header;
-    scavtab[type_ByteCodeClosure] = scav_closure_header;
+    scavtab[CLOSURE_HEADER_WIDETAG] = scav_closure_header;
+    scavtab[FUNCALLABLE_INSTANCE_HEADER_WIDETAG] = scav_closure_header;
 #else
-    scavtab[type_ClosureHeader] = scav_boxed;
-    scavtab[type_FuncallableInstanceHeader] = scav_boxed;
-    scavtab[type_ByteCodeFunction] = scav_boxed;
-    scavtab[type_ByteCodeClosure] = scav_boxed;
+    scavtab[CLOSURE_HEADER_WIDETAG] = scav_boxed;
+    scavtab[FUNCALLABLE_INSTANCE_HEADER_WIDETAG] = scav_boxed;
 #endif
-    scavtab[type_ValueCellHeader] = scav_boxed;
-    scavtab[type_SymbolHeader] = scav_boxed;
-    scavtab[type_BaseChar] = scav_immediate;
-    scavtab[type_Sap] = scav_unboxed;
-    scavtab[type_UnboundMarker] = scav_immediate;
-    scavtab[type_WeakPointer] = scav_weak_pointer;
-    scavtab[type_InstanceHeader] = scav_boxed;
-    scavtab[type_Fdefn] = scav_fdefn;
+    scavtab[VALUE_CELL_HEADER_WIDETAG] = scav_boxed;
+    scavtab[SYMBOL_HEADER_WIDETAG] = scav_boxed;
+    scavtab[BASE_CHAR_WIDETAG] = scav_immediate;
+    scavtab[SAP_WIDETAG] = scav_unboxed;
+    scavtab[UNBOUND_MARKER_WIDETAG] = scav_immediate;
+    scavtab[WEAK_POINTER_WIDETAG] = scav_weak_pointer;
+    scavtab[INSTANCE_HEADER_WIDETAG] = scav_boxed;
+    scavtab[FDEFN_WIDETAG] = scav_fdefn;
 
     /* transport other table, initialized same way as scavtab */
     for (i = 0; i < 256; i++)
        transother[i] = trans_lose;
-    transother[type_Bignum] = trans_unboxed;
-    transother[type_Ratio] = trans_boxed;
-    transother[type_SingleFloat] = trans_unboxed;
-    transother[type_DoubleFloat] = trans_unboxed;
-#ifdef type_LongFloat
-    transother[type_LongFloat] = trans_unboxed;
+    transother[BIGNUM_WIDETAG] = trans_unboxed;
+    transother[RATIO_WIDETAG] = trans_boxed;
+    transother[SINGLE_FLOAT_WIDETAG] = trans_unboxed;
+    transother[DOUBLE_FLOAT_WIDETAG] = trans_unboxed;
+#ifdef LONG_FLOAT_WIDETAG
+    transother[LONG_FLOAT_WIDETAG] = trans_unboxed;
 #endif
-    transother[type_Complex] = trans_boxed;
-#ifdef type_ComplexSingleFloat
-    transother[type_ComplexSingleFloat] = trans_unboxed;
+    transother[COMPLEX_WIDETAG] = trans_boxed;
+#ifdef COMPLEX_SINGLE_FLOAT_WIDETAG
+    transother[COMPLEX_SINGLE_FLOAT_WIDETAG] = trans_unboxed;
 #endif
-#ifdef type_ComplexDoubleFloat
-    transother[type_ComplexDoubleFloat] = trans_unboxed;
+#ifdef COMPLEX_DOUBLE_FLOAT_WIDETAG
+    transother[COMPLEX_DOUBLE_FLOAT_WIDETAG] = trans_unboxed;
 #endif
-#ifdef type_ComplexLongFloat
-    transother[type_ComplexLongFloat] = trans_unboxed;
+#ifdef COMPLEX_LONG_FLOAT_WIDETAG
+    transother[COMPLEX_LONG_FLOAT_WIDETAG] = trans_unboxed;
 #endif
-    transother[type_SimpleArray] = trans_boxed_large;
-    transother[type_SimpleString] = trans_string;
-    transother[type_SimpleBitVector] = trans_vector_bit;
-    transother[type_SimpleVector] = trans_vector;
-    transother[type_SimpleArrayUnsignedByte2] = trans_vector_unsigned_byte_2;
-    transother[type_SimpleArrayUnsignedByte4] = trans_vector_unsigned_byte_4;
-    transother[type_SimpleArrayUnsignedByte8] = trans_vector_unsigned_byte_8;
-    transother[type_SimpleArrayUnsignedByte16] = trans_vector_unsigned_byte_16;
-    transother[type_SimpleArrayUnsignedByte32] = trans_vector_unsigned_byte_32;
-#ifdef type_SimpleArraySignedByte8
-    transother[type_SimpleArraySignedByte8] = trans_vector_unsigned_byte_8;
+    transother[SIMPLE_ARRAY_WIDETAG] = trans_boxed_large;
+    transother[SIMPLE_STRING_WIDETAG] = trans_string;
+    transother[SIMPLE_BIT_VECTOR_WIDETAG] = trans_vector_bit;
+    transother[SIMPLE_VECTOR_WIDETAG] = trans_vector;
+    transother[SIMPLE_ARRAY_UNSIGNED_BYTE_2_WIDETAG] =
+       trans_vector_unsigned_byte_2;
+    transother[SIMPLE_ARRAY_UNSIGNED_BYTE_4_WIDETAG] =
+       trans_vector_unsigned_byte_4;
+    transother[SIMPLE_ARRAY_UNSIGNED_BYTE_8_WIDETAG] =
+       trans_vector_unsigned_byte_8;
+    transother[SIMPLE_ARRAY_UNSIGNED_BYTE_16_WIDETAG] =
+       trans_vector_unsigned_byte_16;
+    transother[SIMPLE_ARRAY_UNSIGNED_BYTE_32_WIDETAG] =
+       trans_vector_unsigned_byte_32;
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_8_WIDETAG
+    transother[SIMPLE_ARRAY_SIGNED_BYTE_8_WIDETAG] =
+       trans_vector_unsigned_byte_8;
 #endif
-#ifdef type_SimpleArraySignedByte16
-    transother[type_SimpleArraySignedByte16] = trans_vector_unsigned_byte_16;
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_16_WIDETAG
+    transother[SIMPLE_ARRAY_SIGNED_BYTE_16_WIDETAG] =
+       trans_vector_unsigned_byte_16;
 #endif
-#ifdef type_SimpleArraySignedByte30
-    transother[type_SimpleArraySignedByte30] = trans_vector_unsigned_byte_32;
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_30_WIDETAG
+    transother[SIMPLE_ARRAY_SIGNED_BYTE_30_WIDETAG] =
+       trans_vector_unsigned_byte_32;
 #endif
-#ifdef type_SimpleArraySignedByte32
-    transother[type_SimpleArraySignedByte32] = trans_vector_unsigned_byte_32;
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_32_WIDETAG
+    transother[SIMPLE_ARRAY_SIGNED_BYTE_32_WIDETAG] =
+       trans_vector_unsigned_byte_32;
 #endif
-    transother[type_SimpleArraySingleFloat] = trans_vector_single_float;
-    transother[type_SimpleArrayDoubleFloat] = trans_vector_double_float;
-#ifdef type_SimpleArrayLongFloat
-    transother[type_SimpleArrayLongFloat] = trans_vector_long_float;
+    transother[SIMPLE_ARRAY_SINGLE_FLOAT_WIDETAG] =
+       trans_vector_single_float;
+    transother[SIMPLE_ARRAY_DOUBLE_FLOAT_WIDETAG] =
+       trans_vector_double_float;
+#ifdef SIMPLE_ARRAY_LONG_FLOAT_WIDETAG
+    transother[SIMPLE_ARRAY_LONG_FLOAT_WIDETAG] =
+       trans_vector_long_float;
 #endif
-#ifdef type_SimpleArrayComplexSingleFloat
-    transother[type_SimpleArrayComplexSingleFloat] = trans_vector_complex_single_float;
+#ifdef SIMPLE_ARRAY_COMPLEX_SINGLE_FLOAT_WIDETAG
+    transother[SIMPLE_ARRAY_COMPLEX_SINGLE_FLOAT_WIDETAG] =
+       trans_vector_complex_single_float;
 #endif
-#ifdef type_SimpleArrayComplexDoubleFloat
-    transother[type_SimpleArrayComplexDoubleFloat] = trans_vector_complex_double_float;
+#ifdef SIMPLE_ARRAY_COMPLEX_DOUBLE_FLOAT_WIDETAG
+    transother[SIMPLE_ARRAY_COMPLEX_DOUBLE_FLOAT_WIDETAG] =
+       trans_vector_complex_double_float;
 #endif
-#ifdef type_SimpleArrayComplexLongFloat
-    transother[type_SimpleArrayComplexLongFloat] = trans_vector_complex_long_float;
+#ifdef SIMPLE_ARRAY_COMPLEX_LONG_FLOAT_WIDETAG
+    transother[SIMPLE_ARRAY_COMPLEX_LONG_FLOAT_WIDETAG] =
+       trans_vector_complex_long_float;
 #endif
-    transother[type_ComplexString] = trans_boxed;
-    transother[type_ComplexBitVector] = trans_boxed;
-    transother[type_ComplexVector] = trans_boxed;
-    transother[type_ComplexArray] = trans_boxed;
-    transother[type_CodeHeader] = trans_code_header;
-    transother[type_FunctionHeader] = trans_function_header;
-    transother[type_ClosureFunctionHeader] = trans_function_header;
-    transother[type_ReturnPcHeader] = trans_return_pc_header;
-    transother[type_ClosureHeader] = trans_boxed;
-    transother[type_FuncallableInstanceHeader] = trans_boxed;
-    transother[type_ByteCodeFunction] = trans_boxed;
-    transother[type_ByteCodeClosure] = trans_boxed;
-    transother[type_ValueCellHeader] = trans_boxed;
-    transother[type_SymbolHeader] = trans_boxed;
-    transother[type_BaseChar] = trans_immediate;
-    transother[type_Sap] = trans_unboxed;
-    transother[type_UnboundMarker] = trans_immediate;
-    transother[type_WeakPointer] = trans_weak_pointer;
-    transother[type_InstanceHeader] = trans_boxed;
-    transother[type_Fdefn] = trans_boxed;
+    transother[COMPLEX_STRING_WIDETAG] = trans_boxed;
+    transother[COMPLEX_BIT_VECTOR_WIDETAG] = trans_boxed;
+    transother[COMPLEX_VECTOR_WIDETAG] = trans_boxed;
+    transother[COMPLEX_ARRAY_WIDETAG] = trans_boxed;
+    transother[CODE_HEADER_WIDETAG] = trans_code_header;
+    transother[SIMPLE_FUN_HEADER_WIDETAG] = trans_fun_header;
+    transother[CLOSURE_FUN_HEADER_WIDETAG] = trans_fun_header;
+    transother[RETURN_PC_HEADER_WIDETAG] = trans_return_pc_header;
+    transother[CLOSURE_HEADER_WIDETAG] = trans_boxed;
+    transother[FUNCALLABLE_INSTANCE_HEADER_WIDETAG] = trans_boxed;
+    transother[VALUE_CELL_HEADER_WIDETAG] = trans_boxed;
+    transother[SYMBOL_HEADER_WIDETAG] = trans_boxed;
+    transother[BASE_CHAR_WIDETAG] = trans_immediate;
+    transother[SAP_WIDETAG] = trans_unboxed;
+    transother[UNBOUND_MARKER_WIDETAG] = trans_immediate;
+    transother[WEAK_POINTER_WIDETAG] = trans_weak_pointer;
+    transother[INSTANCE_HEADER_WIDETAG] = trans_boxed;
+    transother[FDEFN_WIDETAG] = trans_boxed;
 
     /* size table, initialized the same way as scavtab */
     for (i = 0; i < 256; i++)
        sizetab[i] = size_lose;
     for (i = 0; i < 32; i++) {
-       sizetab[type_EvenFixnum|(i<<3)] = size_immediate;
-       sizetab[type_FunctionPointer|(i<<3)] = size_pointer;
-       /* OtherImmediate0 */
-       sizetab[type_ListPointer|(i<<3)] = size_pointer;
-       sizetab[type_OddFixnum|(i<<3)] = size_immediate;
-       sizetab[type_InstancePointer|(i<<3)] = size_pointer;
-       /* OtherImmediate1 */
-       sizetab[type_OtherPointer|(i<<3)] = size_pointer;
+       sizetab[EVEN_FIXNUM_LOWTAG|(i<<3)] = size_immediate;
+       sizetab[FUN_POINTER_LOWTAG|(i<<3)] = size_pointer;
+       /* skipping OTHER_IMMEDIATE_0_LOWTAG */
+       sizetab[LIST_POINTER_LOWTAG|(i<<3)] = size_pointer;
+       sizetab[ODD_FIXNUM_LOWTAG|(i<<3)] = size_immediate;
+       sizetab[INSTANCE_POINTER_LOWTAG|(i<<3)] = size_pointer;
+       /* skipping OTHER_IMMEDIATE_1_LOWTAG */
+       sizetab[OTHER_POINTER_LOWTAG|(i<<3)] = size_pointer;
     }
-    sizetab[type_Bignum] = size_unboxed;
-    sizetab[type_Ratio] = size_boxed;
-    sizetab[type_SingleFloat] = size_unboxed;
-    sizetab[type_DoubleFloat] = size_unboxed;
-#ifdef type_LongFloat
-    sizetab[type_LongFloat] = size_unboxed;
+    sizetab[BIGNUM_WIDETAG] = size_unboxed;
+    sizetab[RATIO_WIDETAG] = size_boxed;
+    sizetab[SINGLE_FLOAT_WIDETAG] = size_unboxed;
+    sizetab[DOUBLE_FLOAT_WIDETAG] = size_unboxed;
+#ifdef LONG_FLOAT_WIDETAG
+    sizetab[LONG_FLOAT_WIDETAG] = size_unboxed;
 #endif
-    sizetab[type_Complex] = size_boxed;
-#ifdef type_ComplexSingleFloat
-    sizetab[type_ComplexSingleFloat] = size_unboxed;
+    sizetab[COMPLEX_WIDETAG] = size_boxed;
+#ifdef COMPLEX_SINGLE_FLOAT_WIDETAG
+    sizetab[COMPLEX_SINGLE_FLOAT_WIDETAG] = size_unboxed;
 #endif
-#ifdef type_ComplexDoubleFloat
-    sizetab[type_ComplexDoubleFloat] = size_unboxed;
+#ifdef COMPLEX_DOUBLE_FLOAT_WIDETAG
+    sizetab[COMPLEX_DOUBLE_FLOAT_WIDETAG] = size_unboxed;
 #endif
-#ifdef type_ComplexLongFloat
-    sizetab[type_ComplexLongFloat] = size_unboxed;
+#ifdef COMPLEX_LONG_FLOAT_WIDETAG
+    sizetab[COMPLEX_LONG_FLOAT_WIDETAG] = size_unboxed;
 #endif
-    sizetab[type_SimpleArray] = size_boxed;
-    sizetab[type_SimpleString] = size_string;
-    sizetab[type_SimpleBitVector] = size_vector_bit;
-    sizetab[type_SimpleVector] = size_vector;
-    sizetab[type_SimpleArrayUnsignedByte2] = size_vector_unsigned_byte_2;
-    sizetab[type_SimpleArrayUnsignedByte4] = size_vector_unsigned_byte_4;
-    sizetab[type_SimpleArrayUnsignedByte8] = size_vector_unsigned_byte_8;
-    sizetab[type_SimpleArrayUnsignedByte16] = size_vector_unsigned_byte_16;
-    sizetab[type_SimpleArrayUnsignedByte32] = size_vector_unsigned_byte_32;
-#ifdef type_SimpleArraySignedByte8
-    sizetab[type_SimpleArraySignedByte8] = size_vector_unsigned_byte_8;
+    sizetab[SIMPLE_ARRAY_WIDETAG] = size_boxed;
+    sizetab[SIMPLE_STRING_WIDETAG] = size_string;
+    sizetab[SIMPLE_BIT_VECTOR_WIDETAG] = size_vector_bit;
+    sizetab[SIMPLE_VECTOR_WIDETAG] = size_vector;
+    sizetab[SIMPLE_ARRAY_UNSIGNED_BYTE_2_WIDETAG] =
+       size_vector_unsigned_byte_2;
+    sizetab[SIMPLE_ARRAY_UNSIGNED_BYTE_4_WIDETAG] =
+       size_vector_unsigned_byte_4;
+    sizetab[SIMPLE_ARRAY_UNSIGNED_BYTE_8_WIDETAG] =
+       size_vector_unsigned_byte_8;
+    sizetab[SIMPLE_ARRAY_UNSIGNED_BYTE_16_WIDETAG] =
+       size_vector_unsigned_byte_16;
+    sizetab[SIMPLE_ARRAY_UNSIGNED_BYTE_32_WIDETAG] =
+       size_vector_unsigned_byte_32;
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_8_WIDETAG
+    sizetab[SIMPLE_ARRAY_SIGNED_BYTE_8_WIDETAG] = size_vector_unsigned_byte_8;
 #endif
-#ifdef type_SimpleArraySignedByte16
-    sizetab[type_SimpleArraySignedByte16] = size_vector_unsigned_byte_16;
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_16_WIDETAG
+    sizetab[SIMPLE_ARRAY_SIGNED_BYTE_16_WIDETAG] =
+       size_vector_unsigned_byte_16;
 #endif
-#ifdef type_SimpleArraySignedByte30
-    sizetab[type_SimpleArraySignedByte30] = size_vector_unsigned_byte_32;
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_30_WIDETAG
+    sizetab[SIMPLE_ARRAY_SIGNED_BYTE_30_WIDETAG] =
+       size_vector_unsigned_byte_32;
 #endif
-#ifdef type_SimpleArraySignedByte32
-    sizetab[type_SimpleArraySignedByte32] = size_vector_unsigned_byte_32;
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_32_WIDETAG
+    sizetab[SIMPLE_ARRAY_SIGNED_BYTE_32_WIDETAG] =
+       size_vector_unsigned_byte_32;
 #endif
-    sizetab[type_SimpleArraySingleFloat] = size_vector_single_float;
-    sizetab[type_SimpleArrayDoubleFloat] = size_vector_double_float;
-#ifdef type_SimpleArrayLongFloat
-    sizetab[type_SimpleArrayLongFloat] = size_vector_long_float;
+    sizetab[SIMPLE_ARRAY_SINGLE_FLOAT_WIDETAG] = size_vector_single_float;
+    sizetab[SIMPLE_ARRAY_DOUBLE_FLOAT_WIDETAG] = size_vector_double_float;
+#ifdef SIMPLE_ARRAY_LONG_FLOAT_WIDETAG
+    sizetab[SIMPLE_ARRAY_LONG_FLOAT_WIDETAG] = size_vector_long_float;
 #endif
-#ifdef type_SimpleArrayComplexSingleFloat
-    sizetab[type_SimpleArrayComplexSingleFloat] = size_vector_complex_single_float;
+#ifdef SIMPLE_ARRAY_COMPLEX_SINGLE_FLOAT_WIDETAG
+    sizetab[SIMPLE_ARRAY_COMPLEX_SINGLE_FLOAT_WIDETAG] =
+       size_vector_complex_single_float;
 #endif
-#ifdef type_SimpleArrayComplexDoubleFloat
-    sizetab[type_SimpleArrayComplexDoubleFloat] = size_vector_complex_double_float;
+#ifdef SIMPLE_ARRAY_COMPLEX_DOUBLE_FLOAT_WIDETAG
+    sizetab[SIMPLE_ARRAY_COMPLEX_DOUBLE_FLOAT_WIDETAG] =
+       size_vector_complex_double_float;
 #endif
-#ifdef type_SimpleArrayComplexLongFloat
-    sizetab[type_SimpleArrayComplexLongFloat] = size_vector_complex_long_float;
+#ifdef SIMPLE_ARRAY_COMPLEX_LONG_FLOAT_WIDETAG
+    sizetab[SIMPLE_ARRAY_COMPLEX_LONG_FLOAT_WIDETAG] =
+       size_vector_complex_long_float;
 #endif
-    sizetab[type_ComplexString] = size_boxed;
-    sizetab[type_ComplexBitVector] = size_boxed;
-    sizetab[type_ComplexVector] = size_boxed;
-    sizetab[type_ComplexArray] = size_boxed;
-    sizetab[type_CodeHeader] = size_code_header;
+    sizetab[COMPLEX_STRING_WIDETAG] = size_boxed;
+    sizetab[COMPLEX_BIT_VECTOR_WIDETAG] = size_boxed;
+    sizetab[COMPLEX_VECTOR_WIDETAG] = size_boxed;
+    sizetab[COMPLEX_ARRAY_WIDETAG] = size_boxed;
+    sizetab[CODE_HEADER_WIDETAG] = size_code_header;
 #if 0
     /* We shouldn't see these, so just lose if it happens. */
-    sizetab[type_FunctionHeader] = size_function_header;
-    sizetab[type_ClosureFunctionHeader] = size_function_header;
-    sizetab[type_ReturnPcHeader] = size_return_pc_header;
+    sizetab[SIMPLE_FUN_HEADER_WIDETAG] = size_function_header;
+    sizetab[CLOSURE_FUN_HEADER_WIDETAG] = size_function_header;
+    sizetab[RETURN_PC_HEADER_WIDETAG] = size_return_pc_header;
 #endif
-    sizetab[type_ClosureHeader] = size_boxed;
-    sizetab[type_FuncallableInstanceHeader] = size_boxed;
-    sizetab[type_ValueCellHeader] = size_boxed;
-    sizetab[type_SymbolHeader] = size_boxed;
-    sizetab[type_BaseChar] = size_immediate;
-    sizetab[type_Sap] = size_unboxed;
-    sizetab[type_UnboundMarker] = size_immediate;
-    sizetab[type_WeakPointer] = size_weak_pointer;
-    sizetab[type_InstanceHeader] = size_boxed;
-    sizetab[type_Fdefn] = size_boxed;
+    sizetab[CLOSURE_HEADER_WIDETAG] = size_boxed;
+    sizetab[FUNCALLABLE_INSTANCE_HEADER_WIDETAG] = size_boxed;
+    sizetab[VALUE_CELL_HEADER_WIDETAG] = size_boxed;
+    sizetab[SYMBOL_HEADER_WIDETAG] = size_boxed;
+    sizetab[BASE_CHAR_WIDETAG] = size_immediate;
+    sizetab[SAP_WIDETAG] = size_unboxed;
+    sizetab[UNBOUND_MARKER_WIDETAG] = size_immediate;
+    sizetab[WEAK_POINTER_WIDETAG] = size_weak_pointer;
+    sizetab[INSTANCE_HEADER_WIDETAG] = size_boxed;
+    sizetab[FDEFN_WIDETAG] = size_boxed;
 }
 \f
 /* Scan an area looking for an object which encloses the given pointer.
@@ -4012,23 +3873,23 @@ search_space(lispobj *start, size_t words, lispobj *pointer)
        size_t count = 1;
        lispobj thing = *start;
 
-       /* If thing is an immediate then this is a cons */
-       if (Pointerp(thing)
+       /* If thing is an immediate then this is a cons. */
+       if (is_lisp_pointer(thing)
            || ((thing & 3) == 0) /* fixnum */
-           || (TypeOf(thing) == type_BaseChar)
-           || (TypeOf(thing) == type_UnboundMarker))
+           || (widetag_of(thing) == BASE_CHAR_WIDETAG)
+           || (widetag_of(thing) == UNBOUND_MARKER_WIDETAG))
            count = 2;
        else
-           count = (sizetab[TypeOf(thing)])(start);
+           count = (sizetab[widetag_of(thing)])(start);
 
-       /* Check whether the pointer is within this object? */
+       /* Check whether the pointer is within this object. */
        if ((pointer >= start) && (pointer < (start+count))) {
            /* found it! */
            /*FSHOW((stderr,"/found %x in %x %x\n", pointer, start, thing));*/
            return(start);
        }
 
-       /* Round up the count */
+       /* Round up the count. */
        count = CEILING(count,2);
 
        start += count;
@@ -4050,7 +3911,7 @@ search_read_only_space(lispobj *pointer)
 static lispobj *
 search_static_space(lispobj *pointer)
 {
-    lispobj* start = (lispobj*)static_space;
+    lispobj* start = (lispobj*)STATIC_SPACE_START;
     lispobj* end = (lispobj*)SymbolValue(STATIC_SPACE_FREE_POINTER);
     if ((pointer < start) || (pointer >= end))
        return NULL;
@@ -4065,7 +3926,7 @@ search_dynamic_space(lispobj *pointer)
     int  page_index = find_page_index(pointer);
     lispobj *start;
 
-    /* Address may be invalid - do some checks. */
+    /* The address may be invalid, so do some checks. */
     if ((page_index == -1) || (page_table[page_index].allocated == FREE_PAGE))
        return NULL;
     start = (lispobj *)((void *)page_address(page_index)
@@ -4073,48 +3934,62 @@ search_dynamic_space(lispobj *pointer)
     return (search_space(start, (pointer+2)-start, pointer));
 }
 
-/* FIXME: There is a strong family resemblance between this function
- * and the function of the same name in purify.c. Would it be possible
- * to implement them as exactly the same function? */
+/* Is there any possibility that pointer is a valid Lisp object
+ * reference, and/or something else (e.g. subroutine call return
+ * address) which should prevent us from moving the referred-to thing? */
 static int
-valid_dynamic_space_pointer(lispobj *pointer)
+possibly_valid_dynamic_space_pointer(lispobj *pointer)
 {
     lispobj *start_addr;
 
-    /* Find the object start address */
+    /* Find the object start address. */
     if ((start_addr = search_dynamic_space(pointer)) == NULL) {
        return 0;
     }
 
     /* We need to allow raw pointers into Code objects for return
-     * addresses. This will also pickup pointers to functions in code
+     * addresses. This will also pick up pointers to functions in code
      * objects. */
-    if (TypeOf(*start_addr) == type_CodeHeader) {
-       /* X Could do some further checks here. */
+    if (widetag_of(*start_addr) == CODE_HEADER_WIDETAG) {
+       /* XXX could do some further checks here */
        return 1;
     }
 
     /* If it's not a return address then it needs to be a valid Lisp
      * pointer. */
-    if (!Pointerp((lispobj)pointer)) {
+    if (!is_lisp_pointer((lispobj)pointer)) {
        return 0;
     }
 
     /* Check that the object pointed to is consistent with the pointer
-     * low tag. */
-    switch (LowtagOf((lispobj)pointer)) {
-    case type_FunctionPointer:
+     * low tag.
+     *
+     * FIXME: It's not safe to rely on the result from this check
+     * before an object is initialized. Thus, if we were interrupted
+     * just as an object had been allocated but not initialized, the
+     * GC relying on this result could bogusly reclaim the memory.
+     * However, we can't really afford to do without this check. So
+     * we should make it safe somehow. 
+     *   (1) Perhaps just review the code to make sure
+     *       that WITHOUT-GCING or WITHOUT-INTERRUPTS or some such
+     *       thing is wrapped around critical sections where allocated
+     *       memory type bits haven't been set.
+     *   (2) Perhaps find some other hack to protect against this, e.g.
+     *       recording the result of the last call to allocate-lisp-memory,
+     *       and returning true from this function when *pointer is
+     *       a reference to that result. */
+    switch (lowtag_of((lispobj)pointer)) {
+    case FUN_POINTER_LOWTAG:
        /* Start_addr should be the enclosing code object, or a closure
-          header. */
-       switch (TypeOf(*start_addr)) {
-       case type_CodeHeader:
+        * header. */
+       switch (widetag_of(*start_addr)) {
+       case CODE_HEADER_WIDETAG:
            /* This case is probably caught above. */
            break;
-       case type_ClosureHeader:
-       case type_FuncallableInstanceHeader:
-       case type_ByteCodeFunction:
-       case type_ByteCodeClosure:
-           if ((int)pointer != ((int)start_addr+type_FunctionPointer)) {
+       case CLOSURE_HEADER_WIDETAG:
+       case FUNCALLABLE_INSTANCE_HEADER_WIDETAG:
+           if ((unsigned)pointer !=
+               ((unsigned)start_addr+FUN_POINTER_LOWTAG)) {
                if (gencgc_verbose)
                    FSHOW((stderr,
                           "/Wf2: %x %x %x\n",
@@ -4130,8 +4005,9 @@ valid_dynamic_space_pointer(lispobj *pointer)
            return 0;
        }
        break;
-    case type_ListPointer:
-       if ((int)pointer != ((int)start_addr+type_ListPointer)) {
+    case LIST_POINTER_LOWTAG:
+       if ((unsigned)pointer !=
+           ((unsigned)start_addr+LIST_POINTER_LOWTAG)) {
            if (gencgc_verbose)
                FSHOW((stderr,
                       "/Wl1: %x %x %x\n",
@@ -4139,14 +4015,14 @@ valid_dynamic_space_pointer(lispobj *pointer)
            return 0;
        }
        /* Is it plausible cons? */
-       if ((Pointerp(start_addr[0])
+       if ((is_lisp_pointer(start_addr[0])
            || ((start_addr[0] & 3) == 0) /* fixnum */
-           || (TypeOf(start_addr[0]) == type_BaseChar)
-           || (TypeOf(start_addr[0]) == type_UnboundMarker))
-          && (Pointerp(start_addr[1])
+           || (widetag_of(start_addr[0]) == BASE_CHAR_WIDETAG)
+           || (widetag_of(start_addr[0]) == UNBOUND_MARKER_WIDETAG))
+          && (is_lisp_pointer(start_addr[1])
               || ((start_addr[1] & 3) == 0) /* fixnum */
-              || (TypeOf(start_addr[1]) == type_BaseChar)
-              || (TypeOf(start_addr[1]) == type_UnboundMarker)))
+              || (widetag_of(start_addr[1]) == BASE_CHAR_WIDETAG)
+              || (widetag_of(start_addr[1]) == UNBOUND_MARKER_WIDETAG)))
            break;
        else {
            if (gencgc_verbose)
@@ -4155,15 +4031,16 @@ valid_dynamic_space_pointer(lispobj *pointer)
                       pointer, start_addr, *start_addr));
            return 0;
        }
-    case type_InstancePointer:
-       if ((int)pointer != ((int)start_addr+type_InstancePointer)) {
+    case INSTANCE_POINTER_LOWTAG:
+       if ((unsigned)pointer !=
+           ((unsigned)start_addr+INSTANCE_POINTER_LOWTAG)) {
            if (gencgc_verbose)
                FSHOW((stderr,
                       "/Wi1: %x %x %x\n",
                       pointer, start_addr, *start_addr));
            return 0;
        }
-       if (TypeOf(start_addr[0]) != type_InstanceHeader) {
+       if (widetag_of(start_addr[0]) != INSTANCE_HEADER_WIDETAG) {
            if (gencgc_verbose)
                FSHOW((stderr,
                       "/Wi2: %x %x %x\n",
@@ -4171,25 +4048,26 @@ valid_dynamic_space_pointer(lispobj *pointer)
            return 0;
        }
        break;
-    case type_OtherPointer:
-       if ((int)pointer != ((int)start_addr+type_OtherPointer)) {
+    case OTHER_POINTER_LOWTAG:
+       if ((unsigned)pointer !=
+           ((int)start_addr+OTHER_POINTER_LOWTAG)) {
            if (gencgc_verbose)
                FSHOW((stderr,
                       "/Wo1: %x %x %x\n",
                       pointer, start_addr, *start_addr));
            return 0;
        }
-       /* Is it plausible?  Not a cons. X should check the headers. */
-       if (Pointerp(start_addr[0]) || ((start_addr[0] & 3) == 0)) {
+       /* Is it plausible?  Not a cons. XXX should check the headers. */
+       if (is_lisp_pointer(start_addr[0]) || ((start_addr[0] & 3) == 0)) {
            if (gencgc_verbose)
                FSHOW((stderr,
                       "/Wo2: %x %x %x\n",
                       pointer, start_addr, *start_addr));
            return 0;
        }
-       switch (TypeOf(start_addr[0])) {
-       case type_UnboundMarker:
-       case type_BaseChar:
+       switch (widetag_of(start_addr[0])) {
+       case UNBOUND_MARKER_WIDETAG:
+       case BASE_CHAR_WIDETAG:
            if (gencgc_verbose)
                FSHOW((stderr,
                       "*Wo3: %x %x %x\n",
@@ -4197,17 +4075,15 @@ valid_dynamic_space_pointer(lispobj *pointer)
            return 0;
 
            /* only pointed to by function pointers? */
-       case type_ClosureHeader:
-       case type_FuncallableInstanceHeader:
-       case type_ByteCodeFunction:
-       case type_ByteCodeClosure:
+       case CLOSURE_HEADER_WIDETAG:
+       case FUNCALLABLE_INSTANCE_HEADER_WIDETAG:
            if (gencgc_verbose)
                FSHOW((stderr,
                       "*Wo4: %x %x %x\n",
                       pointer, start_addr, *start_addr));
            return 0;
 
-       case type_InstanceHeader:
+       case INSTANCE_HEADER_WIDETAG:
            if (gencgc_verbose)
                FSHOW((stderr,
                       "*Wo5: %x %x %x\n",
@@ -4215,68 +4091,68 @@ valid_dynamic_space_pointer(lispobj *pointer)
            return 0;
 
            /* the valid other immediate pointer objects */
-       case type_SimpleVector:
-       case type_Ratio:
-       case type_Complex:
-#ifdef type_ComplexSingleFloat
-       case type_ComplexSingleFloat:
+       case SIMPLE_VECTOR_WIDETAG:
+       case RATIO_WIDETAG:
+       case COMPLEX_WIDETAG:
+#ifdef COMPLEX_SINGLE_FLOAT_WIDETAG
+       case COMPLEX_SINGLE_FLOAT_WIDETAG:
 #endif
-#ifdef type_ComplexDoubleFloat
-       case type_ComplexDoubleFloat:
+#ifdef COMPLEX_DOUBLE_FLOAT_WIDETAG
+       case COMPLEX_DOUBLE_FLOAT_WIDETAG:
 #endif
-#ifdef type_ComplexLongFloat
-       case type_ComplexLongFloat:
+#ifdef COMPLEX_LONG_FLOAT_WIDETAG
+       case COMPLEX_LONG_FLOAT_WIDETAG:
 #endif
-       case type_SimpleArray:
-       case type_ComplexString:
-       case type_ComplexBitVector:
-       case type_ComplexVector:
-       case type_ComplexArray:
-       case type_ValueCellHeader:
-       case type_SymbolHeader:
-       case type_Fdefn:
-       case type_CodeHeader:
-       case type_Bignum:
-       case type_SingleFloat:
-       case type_DoubleFloat:
-#ifdef type_LongFloat
-       case type_LongFloat:
+       case SIMPLE_ARRAY_WIDETAG:
+       case COMPLEX_STRING_WIDETAG:
+       case COMPLEX_BIT_VECTOR_WIDETAG:
+       case COMPLEX_VECTOR_WIDETAG:
+       case COMPLEX_ARRAY_WIDETAG:
+       case VALUE_CELL_HEADER_WIDETAG:
+       case SYMBOL_HEADER_WIDETAG:
+       case FDEFN_WIDETAG:
+       case CODE_HEADER_WIDETAG:
+       case BIGNUM_WIDETAG:
+       case SINGLE_FLOAT_WIDETAG:
+       case DOUBLE_FLOAT_WIDETAG:
+#ifdef LONG_FLOAT_WIDETAG
+       case LONG_FLOAT_WIDETAG:
 #endif
-       case type_SimpleString:
-       case type_SimpleBitVector:
-       case type_SimpleArrayUnsignedByte2:
-       case type_SimpleArrayUnsignedByte4:
-       case type_SimpleArrayUnsignedByte8:
-       case type_SimpleArrayUnsignedByte16:
-       case type_SimpleArrayUnsignedByte32:
-#ifdef type_SimpleArraySignedByte8
-       case type_SimpleArraySignedByte8:
+       case SIMPLE_STRING_WIDETAG:
+       case SIMPLE_BIT_VECTOR_WIDETAG:
+       case SIMPLE_ARRAY_UNSIGNED_BYTE_2_WIDETAG:
+       case SIMPLE_ARRAY_UNSIGNED_BYTE_4_WIDETAG:
+       case SIMPLE_ARRAY_UNSIGNED_BYTE_8_WIDETAG:
+       case SIMPLE_ARRAY_UNSIGNED_BYTE_16_WIDETAG:
+       case SIMPLE_ARRAY_UNSIGNED_BYTE_32_WIDETAG:
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_8_WIDETAG
+       case SIMPLE_ARRAY_SIGNED_BYTE_8_WIDETAG:
 #endif
-#ifdef type_SimpleArraySignedByte16
-       case type_SimpleArraySignedByte16:
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_16_WIDETAG
+       case SIMPLE_ARRAY_SIGNED_BYTE_16_WIDETAG:
 #endif
-#ifdef type_SimpleArraySignedByte30
-       case type_SimpleArraySignedByte30:
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_30_WIDETAG
+       case SIMPLE_ARRAY_SIGNED_BYTE_30_WIDETAG:
 #endif
-#ifdef type_SimpleArraySignedByte32
-       case type_SimpleArraySignedByte32:
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_32_WIDETAG
+       case SIMPLE_ARRAY_SIGNED_BYTE_32_WIDETAG:
 #endif
-       case type_SimpleArraySingleFloat:
-       case type_SimpleArrayDoubleFloat:
-#ifdef type_SimpleArrayLongFloat
-       case type_SimpleArrayLongFloat:
+       case SIMPLE_ARRAY_SINGLE_FLOAT_WIDETAG:
+       case SIMPLE_ARRAY_DOUBLE_FLOAT_WIDETAG:
+#ifdef SIMPLE_ARRAY_LONG_FLOAT_WIDETAG
+       case SIMPLE_ARRAY_LONG_FLOAT_WIDETAG:
 #endif
-#ifdef type_SimpleArrayComplexSingleFloat
-       case type_SimpleArrayComplexSingleFloat:
+#ifdef SIMPLE_ARRAY_COMPLEX_SINGLE_FLOAT_WIDETAG
+       case SIMPLE_ARRAY_COMPLEX_SINGLE_FLOAT_WIDETAG:
 #endif
-#ifdef type_SimpleArrayComplexDoubleFloat
-       case type_SimpleArrayComplexDoubleFloat:
+#ifdef SIMPLE_ARRAY_COMPLEX_DOUBLE_FLOAT_WIDETAG
+       case SIMPLE_ARRAY_COMPLEX_DOUBLE_FLOAT_WIDETAG:
 #endif
-#ifdef type_SimpleArrayComplexLongFloat
-       case type_SimpleArrayComplexLongFloat:
+#ifdef SIMPLE_ARRAY_COMPLEX_LONG_FLOAT_WIDETAG
+       case SIMPLE_ARRAY_COMPLEX_LONG_FLOAT_WIDETAG:
 #endif
-       case type_Sap:
-       case type_WeakPointer:
+       case SAP_WIDETAG:
+       case WEAK_POINTER_WIDETAG:
            break;
 
        default:
@@ -4299,18 +4175,16 @@ valid_dynamic_space_pointer(lispobj *pointer)
     return 1;
 }
 
-/* Adjust large bignum and vector objects. This will adjust the allocated
- * region if the size has shrunk, and move unboxed objects into unboxed
- * pages. The pages are not promoted here, and the promoted region is not
- * added to the new_regions; this is really only designed to be called from
- * preserve_pointer. Shouldn't fail if this is missed, just may delay the
- * moving of objects to unboxed pages, and the freeing of pages. */
+/* Adjust large bignum and vector objects. This will adjust the
+ * allocated region if the size has shrunk, and move unboxed objects
+ * into unboxed pages. The pages are not promoted here, and the
+ * promoted region is not added to the new_regions; this is really
+ * only designed to be called from preserve_pointer(). Shouldn't fail
+ * if this is missed, just may delay the moving of objects to unboxed
+ * pages, and the freeing of pages. */
 static void
 maybe_adjust_large_object(lispobj *where)
 {
-    int tag;
-    lispobj *new;
-    lispobj *source, *dest;
     int first_page;
     int nwords;
 
@@ -4322,43 +4196,43 @@ maybe_adjust_large_object(lispobj *where)
     int boxed;
 
     /* Check whether it's a vector or bignum object. */
-    switch (TypeOf(where[0])) {
-    case type_SimpleVector:
+    switch (widetag_of(where[0])) {
+    case SIMPLE_VECTOR_WIDETAG:
        boxed = BOXED_PAGE;
        break;
-    case type_Bignum:
-    case type_SimpleString:
-    case type_SimpleBitVector:
-    case type_SimpleArrayUnsignedByte2:
-    case type_SimpleArrayUnsignedByte4:
-    case type_SimpleArrayUnsignedByte8:
-    case type_SimpleArrayUnsignedByte16:
-    case type_SimpleArrayUnsignedByte32:
-#ifdef type_SimpleArraySignedByte8
-    case type_SimpleArraySignedByte8:
+    case BIGNUM_WIDETAG:
+    case SIMPLE_STRING_WIDETAG:
+    case SIMPLE_BIT_VECTOR_WIDETAG:
+    case SIMPLE_ARRAY_UNSIGNED_BYTE_2_WIDETAG:
+    case SIMPLE_ARRAY_UNSIGNED_BYTE_4_WIDETAG:
+    case SIMPLE_ARRAY_UNSIGNED_BYTE_8_WIDETAG:
+    case SIMPLE_ARRAY_UNSIGNED_BYTE_16_WIDETAG:
+    case SIMPLE_ARRAY_UNSIGNED_BYTE_32_WIDETAG:
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_8_WIDETAG
+    case SIMPLE_ARRAY_SIGNED_BYTE_8_WIDETAG:
 #endif
-#ifdef type_SimpleArraySignedByte16
-    case type_SimpleArraySignedByte16:
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_16_WIDETAG
+    case SIMPLE_ARRAY_SIGNED_BYTE_16_WIDETAG:
 #endif
-#ifdef type_SimpleArraySignedByte30
-    case type_SimpleArraySignedByte30:
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_30_WIDETAG
+    case SIMPLE_ARRAY_SIGNED_BYTE_30_WIDETAG:
 #endif
-#ifdef type_SimpleArraySignedByte32
-    case type_SimpleArraySignedByte32:
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_32_WIDETAG
+    case SIMPLE_ARRAY_SIGNED_BYTE_32_WIDETAG:
 #endif
-    case type_SimpleArraySingleFloat:
-    case type_SimpleArrayDoubleFloat:
-#ifdef type_SimpleArrayLongFloat
-    case type_SimpleArrayLongFloat:
+    case SIMPLE_ARRAY_SINGLE_FLOAT_WIDETAG:
+    case SIMPLE_ARRAY_DOUBLE_FLOAT_WIDETAG:
+#ifdef SIMPLE_ARRAY_LONG_FLOAT_WIDETAG
+    case SIMPLE_ARRAY_LONG_FLOAT_WIDETAG:
 #endif
-#ifdef type_SimpleArrayComplexSingleFloat
-    case type_SimpleArrayComplexSingleFloat:
+#ifdef SIMPLE_ARRAY_COMPLEX_SINGLE_FLOAT_WIDETAG
+    case SIMPLE_ARRAY_COMPLEX_SINGLE_FLOAT_WIDETAG:
 #endif
-#ifdef type_SimpleArrayComplexDoubleFloat
-    case type_SimpleArrayComplexDoubleFloat:
+#ifdef SIMPLE_ARRAY_COMPLEX_DOUBLE_FLOAT_WIDETAG
+    case SIMPLE_ARRAY_COMPLEX_DOUBLE_FLOAT_WIDETAG:
 #endif
-#ifdef type_SimpleArrayComplexLongFloat
-    case type_SimpleArrayComplexLongFloat:
+#ifdef SIMPLE_ARRAY_COMPLEX_LONG_FLOAT_WIDETAG
+    case SIMPLE_ARRAY_COMPLEX_LONG_FLOAT_WIDETAG:
 #endif
        boxed = UNBOXED_PAGE;
        break;
@@ -4367,7 +4241,7 @@ maybe_adjust_large_object(lispobj *where)
     }
 
     /* Find its current size. */
-    nwords = (sizetab[TypeOf(where[0])])(where);
+    nwords = (sizetab[widetag_of(where[0])])(where);
 
     first_page = find_page_index((void *)where);
     gc_assert(first_page >= 0);
@@ -4438,8 +4312,11 @@ maybe_adjust_large_object(lispobj *where)
        next_page++;
     }
 
-    if ((bytes_freed > 0) && gencgc_verbose)
-       FSHOW((stderr, "/adjust_large_object freed %d\n", bytes_freed));
+    if ((bytes_freed > 0) && gencgc_verbose) {
+       FSHOW((stderr,
+              "/maybe_adjust_large_object() freed %d\n",
+              bytes_freed));
+    }
 
     generations[from_space].bytes_allocated -= bytes_freed;
     bytes_allocated -= bytes_freed;
@@ -4447,21 +4324,21 @@ maybe_adjust_large_object(lispobj *where)
     return;
 }
 
-/* Take a possible pointer to a list object and mark the page_table
- * so that it will not need changing during a GC.
+/* Take a possible pointer to a Lisp object and mark its page in the
+ * page_table so that it will not be relocated during a GC.
  *
  * This involves locating the page it points to, then backing up to
  * the first page that has its first object start at offset 0, and
- * then marking all pages dont_move from the first until a page that ends
- * by being full, or having free gen.
+ * then marking all pages dont_move from the first until a page that
+ * ends by being full, or having free gen.
  *
  * This ensures that objects spanning pages are not broken.
  *
  * It is assumed that all the page static flags have been cleared at
  * the start of a GC.
  *
- * It is also assumed that the current gc_alloc region has been flushed and
- * the tables updated. */
+ * It is also assumed that the current gc_alloc() region has been
+ * flushed and the tables updated. */
 static void
 preserve_pointer(void *addr)
 {
@@ -4470,22 +4347,34 @@ preserve_pointer(void *addr)
     int i;
     unsigned region_allocation;
 
-    /* Address is quite likely to have been invalid - do some checks. */
+    /* quick check 1: Address is quite likely to have been invalid. */
     if ((addr_page_index == -1)
        || (page_table[addr_page_index].allocated == FREE_PAGE)
        || (page_table[addr_page_index].bytes_used == 0)
        || (page_table[addr_page_index].gen != from_space)
-       /* Skip if already marked dont_move */
+       /* Skip if already marked dont_move. */
        || (page_table[addr_page_index].dont_move != 0))
        return;
 
+    /* (Now that we know that addr_page_index is in range, it's
+     * safe to index into page_table[] with it.) */
     region_allocation = page_table[addr_page_index].allocated;
 
-    /* Check the offset within the page */
-    if (((int)addr & 0xfff) > page_table[addr_page_index].bytes_used)
+    /* quick check 2: Check the offset within the page.
+     *
+     * FIXME: The mask should have a symbolic name, and ideally should
+     * be derived from page size instead of hardwired to 0xfff.
+     * (Also fix other uses of 0xfff, elsewhere.) */
+    if (((unsigned)addr & 0xfff) > page_table[addr_page_index].bytes_used)
        return;
 
-    if (enable_pointer_filter && !valid_dynamic_space_pointer(addr))
+    /* Filter out anything which can't be a pointer to a Lisp object
+     * (or, as a special case which also requires dont_move, a return
+     * address referring to something in a CodeObject). This is
+     * expensive but important, since it vastly reduces the
+     * probability that random garbage will be bogusly interpreter as
+     * a pointer which prevents a page from moving. */
+    if (!possibly_valid_dynamic_space_pointer(addr))
        return;
 
     /* Work backwards to find a page with a first_object_offset of 0.
@@ -4493,24 +4382,25 @@ preserve_pointer(void *addr)
      * gen. Assumes the first_object_offset is negative or zero. */
     first_page = addr_page_index;
     while (page_table[first_page].first_object_offset != 0) {
-       first_page--;
+       --first_page;
        /* Do some checks. */
        gc_assert(page_table[first_page].bytes_used == 4096);
        gc_assert(page_table[first_page].gen == from_space);
        gc_assert(page_table[first_page].allocated == region_allocation);
     }
 
-    /* Adjust any large objects before promotion as they won't be copied
-     * after promotion. */
+    /* Adjust any large objects before promotion as they won't be
+     * copied after promotion. */
     if (page_table[first_page].large_object) {
        maybe_adjust_large_object(page_address(first_page));
-       /* If a large object has shrunk then addr may now point to a free
-        * area in which case it's ignored here. Note it gets through the
-        * valid pointer test above because the tail looks like conses. */
+       /* If a large object has shrunk then addr may now point to a
+        * free area in which case it's ignored here. Note it gets
+        * through the valid pointer test above because the tail looks
+        * like conses. */
        if ((page_table[addr_page_index].allocated == FREE_PAGE)
            || (page_table[addr_page_index].bytes_used == 0)
            /* Check the offset within the page. */
-           || (((int)addr & 0xfff)
+           || (((unsigned)addr & 0xfff)
                > page_table[addr_page_index].bytes_used)) {
            FSHOW((stderr,
                   "weird? ignore ptr 0x%x to freed area of large object\n",
@@ -4529,17 +4419,18 @@ preserve_pointer(void *addr)
        /* Mark the page static. */
        page_table[i].dont_move = 1;
 
-       /* Move the page to the new_space. XX I'd rather not do this but
-        * the GC logic is not quite able to copy with the static pages
-        * remaining in the from space. This also requires the generation
-        * bytes_allocated counters be updated. */
+       /* Move the page to the new_space. XX I'd rather not do this
+        * but the GC logic is not quite able to copy with the static
+        * pages remaining in the from space. This also requires the
+        * generation bytes_allocated counters be updated. */
        page_table[i].gen = new_space;
        generations[new_space].bytes_allocated += page_table[i].bytes_used;
        generations[from_space].bytes_allocated -= page_table[i].bytes_used;
 
-       /* It is essential that the pages are not write protected as they
-        * may have pointers into the old-space which need scavenging. They
-        * shouldn't be write protected at this stage. */
+       /* It is essential that the pages are not write protected as
+        * they may have pointers into the old-space which need
+        * scavenging. They shouldn't be write protected at this
+        * stage. */
        gc_assert(!page_table[i].write_protected);
 
        /* Check whether this is the last page in this contiguous block.. */
@@ -4554,85 +4445,21 @@ preserve_pointer(void *addr)
 
     /* Check that the page is now static. */
     gc_assert(page_table[addr_page_index].dont_move != 0);
-
-    return;
 }
-
-#ifdef CONTROL_STACKS
-/* Scavenge the thread stack conservative roots. */
-static void
-scavenge_thread_stacks(void)
-{
-    lispobj thread_stacks = SymbolValue(CONTROL_STACKS);
-    int type = TypeOf(thread_stacks);
-
-    if (LowtagOf(thread_stacks) == type_OtherPointer) {
-       struct vector *vector = (struct vector *) PTR(thread_stacks);
-       int length, i;
-       if (TypeOf(vector->header) != type_SimpleVector)
-           return;
-       length = fixnum_value(vector->length);
-       for (i = 0; i < length; i++) {
-           lispobj stack_obj = vector->data[i];
-           if (LowtagOf(stack_obj) == type_OtherPointer) {
-               struct vector *stack = (struct vector *) PTR(stack_obj);
-               int vector_length;
-               if (TypeOf(stack->header) !=
-                   type_SimpleArrayUnsignedByte32) {
-                   return;
-               }
-               vector_length = fixnum_value(stack->length);
-               if ((gencgc_verbose > 1) && (vector_length <= 0))
-                   FSHOW((stderr,
-                          "/weird? control stack vector length %d\n",
-                          vector_length));
-               if (vector_length > 0) {
-                   lispobj *stack_pointer = (lispobj*)stack->data[0];
-                   if ((stack_pointer < control_stack) ||
-                       (stack_pointer > control_stack_end))
-                       lose("invalid stack pointer %x",
-                            (unsigned)stack_pointer);
-                   if ((stack_pointer > control_stack) &&
-                       (stack_pointer < control_stack_end)) {
-                       unsigned int length = ((int)control_stack_end -
-                                              (int)stack_pointer) / 4;
-                       int j;
-                       if (length >= vector_length) {
-                           lose("invalid stack size %d >= vector length %d",
-                                length,
-                                vector_length);
-                       }
-                       if (gencgc_verbose > 1) {
-                           FSHOW((stderr,
-                                  "scavenging %d words of control stack %d of length %d words.\n",
-                                   length, i, vector_length));
-                       }
-                       for (j = 0; j < length; j++) {
-                           preserve_pointer((void *)stack->data[1+j]);
-                       }
-                   }
-               }
-           }
-       }
-    }
-}
-#endif
-
 \f
 /* If the given page is not write-protected, then scan it for pointers
  * to younger generations or the top temp. generation, if no
  * suspicious pointers are found then the page is write-protected.
  *
- * Care is taken to check for pointers to the current gc_alloc region
- * if it is a younger generation or the temp. generation. This frees
- * the caller from doing a gc_alloc_update_page_tables. Actually the
- * gc_alloc_generation does not need to be checked as this is only
- * called from scavenge_generation when the gc_alloc generation is
+ * Care is taken to check for pointers to the current gc_alloc()
+ * region if it is a younger generation or the temp. generation. This
+ * frees the caller from doing a gc_alloc_update_page_tables(). Actually
+ * the gc_alloc_generation does not need to be checked as this is only
+ * called from scavenge_generation() when the gc_alloc generation is
  * younger, so it just checks if there is a pointer to the current
  * region.
  *
- * We return 1 if the page was write-protected, else 0.
- */
+ * We return 1 if the page was write-protected, else 0. */
 static int
 update_page_write_prot(int page)
 {
@@ -4666,7 +4493,7 @@ update_page_write_prot(int page)
                 && ((page_table[index].gen < gen)
                     || (page_table[index].gen == NUM_GENERATIONS)))
 
-               /* Or does it point within a current gc_alloc region? */
+               /* Or does it point within a current gc_alloc() region? */
                || ((boxed_region.start_addr <= ptr)
                    && (ptr <= boxed_region.free_pointer))
                || ((unboxed_region.start_addr <= ptr)
@@ -4750,7 +4577,7 @@ scavenge_generation(int generation)
            /* Now work forward until the end of this contiguous area
             * is found. A small area is preferred as there is a
             * better chance of its pages being write-protected. */
-           for (last_page = i; ;last_page++)
+           for (last_page = i; ; last_page++)
                /* Check whether this is the last page in this contiguous
                 * block. */
                if ((page_table[last_page].bytes_used < 4096)
@@ -4805,14 +4632,13 @@ scavenge_generation(int generation)
            && (page_table[i].bytes_used != 0)
            && (page_table[i].gen == generation)
            && (page_table[i].write_protected_cleared != 0)) {
-           FSHOW((stderr, "/scavenge_generation %d\n", generation));
+           FSHOW((stderr, "/scavenge_generation() %d\n", generation));
            FSHOW((stderr,
                   "/page bytes_used=%d first_object_offset=%d dont_move=%d\n",
                    page_table[i].bytes_used,
                    page_table[i].first_object_offset,
                    page_table[i].dont_move));
-           lose("write-protected page %d written to in scavenge_generation",
-                i);
+           lose("write to protected page %d in scavenge_generation()", i);
        }
     }
 #endif
@@ -4825,7 +4651,7 @@ scavenge_generation(int generation)
  * newspace generation.
  *
  * To help improve the efficiency, areas written are recorded by
- * gc_alloc and only these scavenged. Sometimes a little more will be
+ * gc_alloc() and only these scavenged. Sometimes a little more will be
  * scavenged, but this causes no harm. An easy check is done that the
  * scavenged bytes equals the number allocated in the previous
  * scavenge.
@@ -4836,7 +4662,7 @@ scavenge_generation(int generation)
  *
  * Write-protected pages could potentially be written by alloc however
  * to avoid having to handle re-scavenging of write-protected pages
- * gc_alloc does not write to write-protected pages.
+ * gc_alloc() does not write to write-protected pages.
  *
  * New areas of objects allocated are recorded alternatively in the two
  * new_areas arrays below. */
@@ -4867,15 +4693,15 @@ scavenge_newspace_generation_one_scan(int generation)
 
            /* The scavenge will start at the first_object_offset of page i.
             *
-            * We need to find the full extent of this contiguous block in case
-            * objects span pages.
+            * We need to find the full extent of this contiguous
+            * block in case objects span pages.
             *
-            * Now work forward until the end of this contiguous area is
-            * found. A small area is preferred as there is a better chance
-            * of its pages being write-protected. */
+            * Now work forward until the end of this contiguous area
+            * is found. A small area is preferred as there is a
+            * better chance of its pages being write-protected. */
            for (last_page = i; ;last_page++) {
-               /* Check whether this is the last page in this contiguous
-                * block */
+               /* Check whether this is the last page in this
+                * contiguous block */
                if ((page_table[last_page].bytes_used < 4096)
                    /* Or it is 4096 and is the last in the block */
                    || (page_table[last_page+1].allocated != BOXED_PAGE)
@@ -4885,9 +4711,9 @@ scavenge_newspace_generation_one_scan(int generation)
                    break;
            }
 
-           /* Do a limited check for write_protected pages. If all pages
-            * are write_protected then no need to scavenge. Except if the
-            * pages are marked dont_move. */
+           /* Do a limited check for write-protected pages. If all
+            * pages are write-protected then no need to scavenge,
+            * except if the pages are marked dont_move. */
            {
                int j, all_wp = 1;
                for (j = i; j <= last_page; j++)
@@ -4896,60 +4722,36 @@ scavenge_newspace_generation_one_scan(int generation)
                        all_wp = 0;
                        break;
                    }
-#if !SC_NS_GEN_CK
-               if (all_wp == 0)
-#endif
-                   {
-                       int size;
-
-                       /* Calculate the size. */
-                       if (last_page == i)
-                           size = (page_table[last_page].bytes_used
-                                   - page_table[i].first_object_offset)/4;
-                       else
-                           size = (page_table[last_page].bytes_used
-                                   + (last_page-i)*4096
-                                   - page_table[i].first_object_offset)/4;
-
-                       {
-#if SC_NS_GEN_CK
-                           int a1 = bytes_allocated;
-#endif
-                           /* FSHOW((stderr,
-                                  "/scavenge(%x,%d)\n",
-                                  page_address(i)
-                                  + page_table[i].first_object_offset,
-                                  size)); */
 
-                           new_areas_ignore_page = last_page;
+               if (!all_wp) {
+                   int size;
 
-                           scavenge(page_address(i)+page_table[i].first_object_offset,size);
+                   /* Calculate the size. */
+                   if (last_page == i)
+                       size = (page_table[last_page].bytes_used
+                               - page_table[i].first_object_offset)/4;
+                   else
+                       size = (page_table[last_page].bytes_used
+                               + (last_page-i)*4096
+                               - page_table[i].first_object_offset)/4;
+                   
+                   {
+                       new_areas_ignore_page = last_page;
+                       
+                       scavenge(page_address(i) +
+                                page_table[i].first_object_offset,
+                                size);
 
-#if SC_NS_GEN_CK
-                           /* Flush the alloc regions updating the tables. */
-                           gc_alloc_update_page_tables(0, &boxed_region);
-                           gc_alloc_update_page_tables(1, &unboxed_region);
-
-                           if ((all_wp != 0)  && (a1 != bytes_allocated)) {
-                               FSHOW((stderr,
-                                      "alloc'ed over %d to %d\n",
-                                      i, last_page));
-                               FSHOW((stderr,
-                                      "/page: bytes_used=%d first_object_offset=%d dont_move=%d wp=%d wpc=%d\n",
-                                       page_table[i].bytes_used,
-                                       page_table[i].first_object_offset,
-                                       page_table[i].dont_move,
-                                       page_table[i].write_protected,
-                                       page_table[i].write_protected_cleared));
-                           }
-#endif
-                       }
                    }
+               }
            }
 
            i = last_page;
        }
     }
+    FSHOW((stderr,
+          "/done with one full scan of newspace generation %d\n",
+          generation));
 }
 
 /* Do a complete scavenge of the newspace generation. */
@@ -4958,28 +4760,19 @@ scavenge_newspace_generation(int generation)
 {
     int i;
 
-    /* the new_areas array currently being written to by gc_alloc */
-    struct new_area  (*current_new_areas)[] = &new_areas_1;
+    /* the new_areas array currently being written to by gc_alloc() */
+    struct new_area (*current_new_areas)[] = &new_areas_1;
     int current_new_areas_index;
-    int current_new_areas_allocated;
 
     /* the new_areas created but the previous scavenge cycle */
-    struct new_area  (*previous_new_areas)[] = NULL;
+    struct new_area (*previous_new_areas)[] = NULL;
     int previous_new_areas_index;
-    int previous_new_areas_allocated;
-
-#define SC_NS_GEN_CK 0
-#if SC_NS_GEN_CK
-    /* Clear the write_protected_cleared flags on all pages. */
-    for (i = 0; i < NUM_PAGES; i++)
-       page_table[i].write_protected_cleared = 0;
-#endif
 
     /* Flush the current regions updating the tables. */
     gc_alloc_update_page_tables(0, &boxed_region);
     gc_alloc_update_page_tables(1, &unboxed_region);
 
-    /* Turn on the recording of new areas by gc_alloc. */
+    /* Turn on the recording of new areas by gc_alloc(). */
     new_areas = current_new_areas;
     new_areas_index = 0;
 
@@ -5019,12 +4812,13 @@ scavenge_newspace_generation(int generation)
        else
            current_new_areas = &new_areas_1;
 
-       /* Set up for gc_alloc. */
+       /* Set up for gc_alloc(). */
        new_areas = current_new_areas;
        new_areas_index = 0;
 
        /* Check whether previous_new_areas had overflowed. */
        if (previous_new_areas_index >= NUM_NEW_AREAS) {
+
            /* New areas of objects allocated have been lost so need to do a
             * full scan to be sure! If this becomes a problem try
             * increasing NUM_NEW_AREAS. */
@@ -5043,20 +4837,18 @@ scavenge_newspace_generation(int generation)
            /* Flush the current regions updating the tables. */
            gc_alloc_update_page_tables(0, &boxed_region);
            gc_alloc_update_page_tables(1, &unboxed_region);
+
        } else {
+
            /* Work through previous_new_areas. */
            for (i = 0; i < previous_new_areas_index; i++) {
+               /* FIXME: All these bare *4 and /4 should be something
+                * like BYTES_PER_WORD or WBYTES. */
                int page = (*previous_new_areas)[i].page;
                int offset = (*previous_new_areas)[i].offset;
                int size = (*previous_new_areas)[i].size / 4;
                gc_assert((*previous_new_areas)[i].size % 4 == 0);
-       
-               /* FIXME: All these bare *4 and /4 should be something
-                * like BYTES_PER_WORD or WBYTES. */
 
-               /*FSHOW((stderr,
-                        "/S page %d offset %d size %d\n",
-                        page, offset, size*4));*/
                scavenge(page_address(page)+offset, size);
            }
 
@@ -5072,7 +4864,7 @@ scavenge_newspace_generation(int generation)
                 current_new_areas_index));*/
     }
 
-    /* Turn off recording of areas allocated by gc_alloc. */
+    /* Turn off recording of areas allocated by gc_alloc(). */
     record_new_objects = 0;
 
 #if SC_NS_GEN_CK
@@ -5099,14 +4891,13 @@ scavenge_newspace_generation(int generation)
 static void
 unprotect_oldspace(void)
 {
-    int bytes_freed = 0;
     int i;
 
     for (i = 0; i < last_free_page; i++) {
        if ((page_table[i].allocated != FREE_PAGE)
            && (page_table[i].bytes_used != 0)
            && (page_table[i].gen == from_space)) {
-           void *page_start, *addr;
+           void *page_start;
 
            page_start = (void *)page_address(i);
 
@@ -5212,6 +5003,7 @@ free_oldspace(void)
     return bytes_freed;
 }
 \f
+#if 0
 /* Print some information about a pointer at the given address. */
 static void
 print_ptr(lispobj *addr)
@@ -5221,7 +5013,7 @@ print_ptr(lispobj *addr)
 
     if (pi1 != -1)
        fprintf(stderr,"  %x: page %d  alloc %d  gen %d  bytes_used %d  offset %d  dont_move %d\n",
-               addr,
+               (unsigned int) addr,
                pi1,
                page_table[pi1].allocated,
                page_table[pi1].gen,
@@ -5239,28 +5031,29 @@ print_ptr(lispobj *addr)
            *(addr+3),
            *(addr+4));
 }
+#endif
 
 extern int undefined_tramp;
 
 static void
-verify_space(lispobj*start, size_t words)
+verify_space(lispobj *start, size_t words)
 {
-    int dynamic_space = (find_page_index((void*)start) != -1);
-    int readonly_space =
-       (READ_ONLY_SPACE_START <= (int)start &&
-        (int)start < SymbolValue(READ_ONLY_SPACE_FREE_POINTER));
+    int is_in_dynamic_space = (find_page_index((void*)start) != -1);
+    int is_in_readonly_space =
+       (READ_ONLY_SPACE_START <= (unsigned)start &&
+        (unsigned)start < SymbolValue(READ_ONLY_SPACE_FREE_POINTER));
 
     while (words > 0) {
        size_t count = 1;
        lispobj thing = *(lispobj*)start;
 
-       if (Pointerp(thing)) {
+       if (is_lisp_pointer(thing)) {
            int page_index = find_page_index((void*)thing);
            int to_readonly_space =
                (READ_ONLY_SPACE_START <= thing &&
                 thing < SymbolValue(READ_ONLY_SPACE_FREE_POINTER));
            int to_static_space =
-               ((int)static_space <= thing &&
+               (STATIC_SPACE_START <= thing &&
                 thing < SymbolValue(STATIC_SPACE_FREE_POINTER));
 
            /* Does it point to the dynamic space? */
@@ -5271,12 +5064,12 @@ verify_space(lispobj*start, size_t words)
                    && (page_table[page_index].bytes_used == 0))
                    lose ("Ptr %x @ %x sees free page.", thing, start);
                /* Check that it doesn't point to a forwarding pointer! */
-               if (*((lispobj *)PTR(thing)) == 0x01) {
+               if (*((lispobj *)native_pointer(thing)) == 0x01) {
                    lose("Ptr %x @ %x sees forwarding ptr.", thing, start);
                }
                /* Check that its not in the RO space as it would then be a
                 * pointer from the RO to the dynamic space. */
-               if (readonly_space) {
+               if (is_in_readonly_space) {
                    lose("ptr to dynamic space %x from RO space %x",
                         thing, start);
                }
@@ -5284,12 +5077,12 @@ verify_space(lispobj*start, size_t words)
                 * it down a lot (so it's commented out).
                 *
                 * FIXME: Add a variable to enable this dynamically. */
-               /* if (!valid_dynamic_space_pointer((lispobj *)thing)) {
+               /* if (!possibly_valid_dynamic_space_pointer((lispobj *)thing)) {
                 *     lose("ptr %x to invalid object %x", thing, start); */
            } else {
                /* Verify that it points to another valid space. */
                if (!to_readonly_space && !to_static_space
-                   && (thing != (int)&undefined_tramp)) {
+                   && (thing != (unsigned)&undefined_tramp)) {
                    lose("Ptr %x @ %x sees junk.", thing, start);
                }
            }
@@ -5297,47 +5090,51 @@ verify_space(lispobj*start, size_t words)
            if (thing & 0x3) { /* Skip fixnums. FIXME: There should be an
                                * is_fixnum for this. */
 
-               switch(TypeOf(*start)) {
+               switch(widetag_of(*start)) {
 
                    /* boxed objects */
-               case type_SimpleVector:
-               case type_Ratio:
-               case type_Complex:
-               case type_SimpleArray:
-               case type_ComplexString:
-               case type_ComplexBitVector:
-               case type_ComplexVector:
-               case type_ComplexArray:
-               case type_ClosureHeader:
-               case type_FuncallableInstanceHeader:
-               case type_ByteCodeFunction:
-               case type_ByteCodeClosure:
-               case type_ValueCellHeader:
-               case type_SymbolHeader:
-               case type_BaseChar:
-               case type_UnboundMarker:
-               case type_InstanceHeader:
-               case type_Fdefn:
+               case SIMPLE_VECTOR_WIDETAG:
+               case RATIO_WIDETAG:
+               case COMPLEX_WIDETAG:
+               case SIMPLE_ARRAY_WIDETAG:
+               case COMPLEX_STRING_WIDETAG:
+               case COMPLEX_BIT_VECTOR_WIDETAG:
+               case COMPLEX_VECTOR_WIDETAG:
+               case COMPLEX_ARRAY_WIDETAG:
+               case CLOSURE_HEADER_WIDETAG:
+               case FUNCALLABLE_INSTANCE_HEADER_WIDETAG:
+               case VALUE_CELL_HEADER_WIDETAG:
+               case SYMBOL_HEADER_WIDETAG:
+               case BASE_CHAR_WIDETAG:
+               case UNBOUND_MARKER_WIDETAG:
+               case INSTANCE_HEADER_WIDETAG:
+               case FDEFN_WIDETAG:
                    count = 1;
                    break;
 
-               case type_CodeHeader:
+               case CODE_HEADER_WIDETAG:
                    {
                        lispobj object = *start;
                        struct code *code;
                        int nheader_words, ncode_words, nwords;
                        lispobj fheaderl;
-                       struct function *fheaderp;
+                       struct simple_fun *fheaderp;
 
                        code = (struct code *) start;
 
                        /* Check that it's not in the dynamic space.
                         * FIXME: Isn't is supposed to be OK for code
                         * objects to be in the dynamic space these days? */
-                       if (dynamic_space
+                       if (is_in_dynamic_space
                            /* It's ok if it's byte compiled code. The trace
                             * table offset will be a fixnum if it's x86
-                            * compiled code - check. */
+                            * compiled code - check.
+                            *
+                            * FIXME: #^#@@! lack of abstraction here..
+                            * This line can probably go away now that
+                            * there's no byte compiler, but I've got
+                            * too much to worry about right now to try
+                            * to make sure. -- WHN 2001-10-06 */
                            && !(code->trace_table_offset & 0x3)
                            /* Only when enabled */
                            && verify_dynamic_code_check) {
@@ -5357,8 +5154,9 @@ verify_space(lispobj*start, size_t words)
                         * the code data block. */
                        fheaderl = code->entry_points;
                        while (fheaderl != NIL) {
-                           fheaderp = (struct function *) PTR(fheaderl);
-                           gc_assert(TypeOf(fheaderp->header) == type_FunctionHeader);
+                           fheaderp =
+                               (struct simple_fun *) native_pointer(fheaderl);
+                           gc_assert(widetag_of(fheaderp->header) == SIMPLE_FUN_HEADER_WIDETAG);
                            verify_space(&fheaderp->name, 1);
                            verify_space(&fheaderp->arglist, 1);
                            verify_space(&fheaderp->type, 1);
@@ -5369,57 +5167,57 @@ verify_space(lispobj*start, size_t words)
                    }
        
                    /* unboxed objects */
-               case type_Bignum:
-               case type_SingleFloat:
-               case type_DoubleFloat:
-#ifdef type_ComplexLongFloat
-               case type_LongFloat:
+               case BIGNUM_WIDETAG:
+               case SINGLE_FLOAT_WIDETAG:
+               case DOUBLE_FLOAT_WIDETAG:
+#ifdef COMPLEX_LONG_FLOAT_WIDETAG
+               case LONG_FLOAT_WIDETAG:
 #endif
-#ifdef type_ComplexSingleFloat
-               case type_ComplexSingleFloat:
+#ifdef COMPLEX_SINGLE_FLOAT_WIDETAG
+               case COMPLEX_SINGLE_FLOAT_WIDETAG:
 #endif
-#ifdef type_ComplexDoubleFloat
-               case type_ComplexDoubleFloat:
+#ifdef COMPLEX_DOUBLE_FLOAT_WIDETAG
+               case COMPLEX_DOUBLE_FLOAT_WIDETAG:
 #endif
-#ifdef type_ComplexLongFloat
-               case type_ComplexLongFloat:
+#ifdef COMPLEX_LONG_FLOAT_WIDETAG
+               case COMPLEX_LONG_FLOAT_WIDETAG:
 #endif
-               case type_SimpleString:
-               case type_SimpleBitVector:
-               case type_SimpleArrayUnsignedByte2:
-               case type_SimpleArrayUnsignedByte4:
-               case type_SimpleArrayUnsignedByte8:
-               case type_SimpleArrayUnsignedByte16:
-               case type_SimpleArrayUnsignedByte32:
-#ifdef type_SimpleArraySignedByte8
-               case type_SimpleArraySignedByte8:
+               case SIMPLE_STRING_WIDETAG:
+               case SIMPLE_BIT_VECTOR_WIDETAG:
+               case SIMPLE_ARRAY_UNSIGNED_BYTE_2_WIDETAG:
+               case SIMPLE_ARRAY_UNSIGNED_BYTE_4_WIDETAG:
+               case SIMPLE_ARRAY_UNSIGNED_BYTE_8_WIDETAG:
+               case SIMPLE_ARRAY_UNSIGNED_BYTE_16_WIDETAG:
+               case SIMPLE_ARRAY_UNSIGNED_BYTE_32_WIDETAG:
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_8_WIDETAG
+               case SIMPLE_ARRAY_SIGNED_BYTE_8_WIDETAG:
 #endif
-#ifdef type_SimpleArraySignedByte16
-               case type_SimpleArraySignedByte16:
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_16_WIDETAG
+               case SIMPLE_ARRAY_SIGNED_BYTE_16_WIDETAG:
 #endif
-#ifdef type_SimpleArraySignedByte30
-               case type_SimpleArraySignedByte30:
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_30_WIDETAG
+               case SIMPLE_ARRAY_SIGNED_BYTE_30_WIDETAG:
 #endif
-#ifdef type_SimpleArraySignedByte32
-               case type_SimpleArraySignedByte32:
+#ifdef SIMPLE_ARRAY_SIGNED_BYTE_32_WIDETAG
+               case SIMPLE_ARRAY_SIGNED_BYTE_32_WIDETAG:
 #endif
-               case type_SimpleArraySingleFloat:
-               case type_SimpleArrayDoubleFloat:
-#ifdef type_SimpleArrayComplexLongFloat
-               case type_SimpleArrayLongFloat:
+               case SIMPLE_ARRAY_SINGLE_FLOAT_WIDETAG:
+               case SIMPLE_ARRAY_DOUBLE_FLOAT_WIDETAG:
+#ifdef SIMPLE_ARRAY_COMPLEX_LONG_FLOAT_WIDETAG
+               case SIMPLE_ARRAY_LONG_FLOAT_WIDETAG:
 #endif
-#ifdef type_SimpleArrayComplexSingleFloat
-               case type_SimpleArrayComplexSingleFloat:
+#ifdef SIMPLE_ARRAY_COMPLEX_SINGLE_FLOAT_WIDETAG
+               case SIMPLE_ARRAY_COMPLEX_SINGLE_FLOAT_WIDETAG:
 #endif
-#ifdef type_SimpleArrayComplexDoubleFloat
-               case type_SimpleArrayComplexDoubleFloat:
+#ifdef SIMPLE_ARRAY_COMPLEX_DOUBLE_FLOAT_WIDETAG
+               case SIMPLE_ARRAY_COMPLEX_DOUBLE_FLOAT_WIDETAG:
 #endif
-#ifdef type_SimpleArrayComplexLongFloat
-               case type_SimpleArrayComplexLongFloat:
+#ifdef SIMPLE_ARRAY_COMPLEX_LONG_FLOAT_WIDETAG
+               case SIMPLE_ARRAY_COMPLEX_LONG_FLOAT_WIDETAG:
 #endif
-               case type_Sap:
-               case type_WeakPointer:
-                   count = (sizetab[TypeOf(*start)])(start);
+               case SAP_WIDETAG:
+               case WEAK_POINTER_WIDETAG:
+                   count = (sizetab[widetag_of(*start)])(start);
                    break;
 
                default:
@@ -5435,19 +5233,25 @@ verify_space(lispobj*start, size_t words)
 static void
 verify_gc(void)
 {
+    /* FIXME: It would be nice to make names consistent so that
+     * foo_size meant size *in* *bytes* instead of size in some
+     * arbitrary units. (Yes, this caused a bug, how did you guess?:-)
+     * Some counts of lispobjs are called foo_count; it might be good
+     * to grep for all foo_size and rename the appropriate ones to
+     * foo_count. */
     int read_only_space_size =
        (lispobj*)SymbolValue(READ_ONLY_SPACE_FREE_POINTER)
        - (lispobj*)READ_ONLY_SPACE_START;
     int static_space_size =
        (lispobj*)SymbolValue(STATIC_SPACE_FREE_POINTER)
-       - (lispobj*)static_space;
+       - (lispobj*)STATIC_SPACE_START;
     int binding_stack_size =
        (lispobj*)SymbolValue(BINDING_STACK_POINTER)
        - (lispobj*)BINDING_STACK_START;
 
     verify_space((lispobj*)READ_ONLY_SPACE_START, read_only_space_size);
-    verify_space((lispobj*)static_space, static_space_size);
-    verify_space((lispobj*)BINDING_STACK_START, binding_stack_size);
+    verify_space((lispobj*)STATIC_SPACE_START   , static_space_size);
+    verify_space((lispobj*)BINDING_STACK_START  , binding_stack_size);
 }
 
 static void
@@ -5488,7 +5292,7 @@ verify_generation(int  generation)
     }
 }
 
-/* Check the all the free space is zero filled. */
+/* Check that all the free space is zero filled. */
 static void
 verify_zero_fill(void)
 {
@@ -5508,7 +5312,7 @@ verify_zero_fill(void)
        } else {
            int free_bytes = 4096 - page_table[page].bytes_used;
            if (free_bytes > 0) {
-               int *start_addr = (int *)((int)page_address(page)
+               int *start_addr = (int *)((unsigned)page_address(page)
                                          + page_table[page].bytes_used);
                int size = free_bytes / 4;
                int i;
@@ -5581,15 +5385,14 @@ write_protect_generation_pages(int generation)
     }
 }
 
-/* Garbage collect a generation. If raise is 0 the remains of the
+/* Garbage collect a generation. If raise is 0 then the remains of the
  * generation are not raised to the next generation. */
 static void
 garbage_collect_generation(int generation, int raise)
 {
-    unsigned long allocated = bytes_allocated;
     unsigned long bytes_freed;
     unsigned long i;
-    unsigned long read_only_space_size, static_space_size;
+    unsigned long static_space_size;
 
     gc_assert(generation <= (NUM_GENERATIONS-1));
 
@@ -5628,35 +5431,36 @@ garbage_collect_generation(int generation, int raise)
     /* Un-write-protect the old-space pages. This is essential for the
      * promoted pages as they may contain pointers into the old-space
      * which need to be scavenged. It also helps avoid unnecessary page
-     * faults as forwarding pointer are written into them. They need to
+     * faults as forwarding pointers are written into them. They need to
      * be un-protected anyway before unmapping later. */
     unprotect_oldspace();
 
     /* Scavenge the stack's conservative roots. */
     {
-       lispobj **ptr;
-       for (ptr = (lispobj **)CONTROL_STACK_END-1;
-            ptr > (lispobj **)&raise; ptr--)
+       void **ptr;
+       for (ptr = (void **)CONTROL_STACK_END - 1;
+            ptr > (void **)&raise;
+            ptr--) {
            preserve_pointer(*ptr);
+       }
     }
-#ifdef CONTROL_STACKS
-    scavenge_thread_stacks();
-#endif
 
+#if QSHOW
     if (gencgc_verbose > 1) {
        int num_dont_move_pages = count_dont_move_pages();
-       FSHOW((stderr,
-              "/non-movable pages due to conservative pointers = %d (%d bytes)\n",
-              num_dont_move_pages,
-              /* FIXME: 4096 should be symbolic constant here and
-               * prob'ly elsewhere too. */
-              num_dont_move_pages * 4096));
+       fprintf(stderr,
+               "/non-movable pages due to conservative pointers = %d (%d bytes)\n",
+               num_dont_move_pages,
+               /* FIXME: 4096 should be symbolic constant here and
+                * prob'ly elsewhere too. */
+               num_dont_move_pages * 4096);
     }
+#endif
 
     /* Scavenge all the rest of the roots. */
 
     /* Scavenge the Lisp functions of the interrupt handlers, taking
-     * care to avoid SIG_DFL, SIG_IGN. */
+     * care to avoid SIG_DFL and SIG_IGN. */
     for (i = 0; i < NSIG; i++) {
        union interrupt_handler handler = interrupt_handlers[i];
        if (!ARE_SAME_HANDLER(handler.c, SIG_IGN) &&
@@ -5666,38 +5470,59 @@ garbage_collect_generation(int generation, int raise)
     }
 
     /* Scavenge the binding stack. */
-    scavenge(binding_stack,
-            (lispobj *)SymbolValue(BINDING_STACK_POINTER) - binding_stack);
-
+    scavenge((lispobj *) BINDING_STACK_START,
+            (lispobj *)SymbolValue(BINDING_STACK_POINTER) -
+            (lispobj *)BINDING_STACK_START);
+
+    /* The original CMU CL code had scavenge-read-only-space code
+     * controlled by the Lisp-level variable
+     * *SCAVENGE-READ-ONLY-SPACE*. It was disabled by default, and it
+     * wasn't documented under what circumstances it was useful or
+     * safe to turn it on, so it's been turned off in SBCL. If you
+     * want/need this functionality, and can test and document it,
+     * please submit a patch. */
+#if 0
     if (SymbolValue(SCAVENGE_READ_ONLY_SPACE) != NIL) {
-       read_only_space_size =
-           (lispobj *)SymbolValue(READ_ONLY_SPACE_FREE_POINTER)
-           - read_only_space;
+       unsigned long read_only_space_size =
+           (lispobj*)SymbolValue(READ_ONLY_SPACE_FREE_POINTER) -
+           (lispobj*)READ_ONLY_SPACE_START;
        FSHOW((stderr,
               "/scavenge read only space: %d bytes\n",
               read_only_space_size * sizeof(lispobj)));
-       scavenge(read_only_space, read_only_space_size);
+       scavenge( (lispobj *) READ_ONLY_SPACE_START, read_only_space_size);
     }
+#endif
 
-    static_space_size = (lispobj *)SymbolValue(STATIC_SPACE_FREE_POINTER)
-       - static_space;
-    if (gencgc_verbose > 1)
+    /* Scavenge static space. */
+    static_space_size =
+       (lispobj *)SymbolValue(STATIC_SPACE_FREE_POINTER) -
+       (lispobj *)STATIC_SPACE_START;
+    if (gencgc_verbose > 1) {
        FSHOW((stderr,
               "/scavenge static space: %d bytes\n",
               static_space_size * sizeof(lispobj)));
-    scavenge(static_space, static_space_size);
+    }
+    scavenge( (lispobj *) STATIC_SPACE_START, static_space_size);
 
     /* All generations but the generation being GCed need to be
      * scavenged. The new_space generation needs special handling as
      * objects may be moved in - it is handled separately below. */
-    for (i = 0; i < NUM_GENERATIONS; i++)
-       if ((i != generation) && (i != new_space))
+    for (i = 0; i < NUM_GENERATIONS; i++) {
+       if ((i != generation) && (i != new_space)) {
            scavenge_generation(i);
+       }
+    }
 
     /* Finally scavenge the new_space generation. Keep going until no
      * more objects are moved into the new generation */
     scavenge_newspace_generation(new_space);
 
+    /* FIXME: I tried reenabling this check when debugging unrelated
+     * GC weirdness ca. sbcl-0.6.12.45, and it failed immediately.
+     * Since the current GC code seems to work well, I'm guessing that
+     * this debugging code is just stale, but I haven't tried to
+     * figure it out. It should be figured out and then either made to
+     * work or just deleted. */
 #define RESCAN_CHECK 0
 #if RESCAN_CHECK
     /* As a check re-scavenge the newspace once; no new objects should
@@ -5768,7 +5593,7 @@ garbage_collect_generation(int generation, int raise)
        ++generations[generation].num_gc;
 }
 
-/* Update last_free_page then ALLOCATION_POINTER */
+/* Update last_free_page, then SymbolValue(ALLOCATION_POINTER). */
 int
 update_x86_dynamic_space_free_pointer(void)
 {
@@ -5784,6 +5609,7 @@ update_x86_dynamic_space_free_pointer(void)
 
     SetSymbolValue(ALLOCATION_POINTER,
                   (lispobj)(((char *)heap_base) + last_free_page*4096));
+    return 0; /* dummy value: return something ... */
 }
 
 /* GC all generations below last_gen, raising their objects to the
@@ -5840,7 +5666,7 @@ collect_garbage(unsigned last_gen)
 
        if (gencgc_verbose > 1) {
            FSHOW((stderr,
-                  "Starting GC of generation %d with raise=%d alloc=%d trig=%d GCs=%d\n",
+                  "starting GC of generation %d with raise=%d alloc=%d trig=%d GCs=%d\n",
                   gen,
                   raise,
                   generations[gen].bytes_allocated,
@@ -5848,8 +5674,8 @@ collect_garbage(unsigned last_gen)
                   generations[gen].num_gc));
        }
 
-       /* If an older generation is being filled then update its memory
-        * age. */
+       /* If an older generation is being filled, then update its
+        * memory age. */
        if (raise == 1) {
            generations[gen+1].cum_sum_bytes_allocated +=
                generations[gen+1].bytes_allocated;
@@ -5900,15 +5726,15 @@ collect_garbage(unsigned last_gen)
        write_protect_generation_pages(gen_to_wp);
     }
 
-    /* Set gc_alloc back to generation 0. The current regions should
-     * be flushed after the above GCs */
+    /* Set gc_alloc() back to generation 0. The current regions should
+     * be flushed after the above GCs. */
     gc_assert((boxed_region.free_pointer - boxed_region.start_addr) == 0);
     gc_alloc_generation = 0;
 
     update_x86_dynamic_space_free_pointer();
 
-    /* This is now done by Lisp SCRUB-CONTROL-STACK in Lisp SUB-GC, so we
-     * needn't do it here: */
+    /* This is now done by Lisp SCRUB-CONTROL-STACK in Lisp SUB-GC, so
+     * we needn't do it here: */
     /*  zero_stack();*/
 
     current_region_free_pointer = boxed_region.free_pointer;
@@ -5920,7 +5746,7 @@ collect_garbage(unsigned last_gen)
 /* This is called by Lisp PURIFY when it is finished. All live objects
  * will have been moved to the RO and Static heaps. The dynamic space
  * will need a full re-initialization. We don't bother having Lisp
- * PURIFY flush the current gc_alloc region, as the page_tables are
+ * PURIFY flush the current gc_alloc() region, as the page_tables are
  * re-initialized, and every page is zeroed to be sure. */
 void
 gc_free_heap(void)
@@ -5958,14 +5784,11 @@ gc_free_heap(void)
                     addr);
            }
        } else if (gencgc_zero_check_during_free_heap) {
-           int *page_start, i;
-
            /* Double-check that the page is zero filled. */
+           int *page_start, i;
            gc_assert(page_table[page].allocated == FREE_PAGE);
            gc_assert(page_table[page].bytes_used == 0);
-
-           page_start = (int *)page_address(i);
-
+           page_start = (int *)page_address(page);
            for (i=0; i<1024; i++) {
                if (page_start[i] != 0) {
                    lose("free region not zero at %x", page_start + i);
@@ -5991,14 +5814,13 @@ gc_free_heap(void)
     if (gencgc_verbose > 1)
        print_generation_stats(0);
 
-    /* Initialize gc_alloc */
+    /* Initialize gc_alloc(). */
     gc_alloc_generation = 0;
     boxed_region.first_page = 0;
     boxed_region.last_page = -1;
     boxed_region.start_addr = page_address(0);
     boxed_region.free_pointer = page_address(0);
     boxed_region.end_addr = page_address(0);
-
     unboxed_region.first_page = 0;
     unboxed_region.last_page = -1;
     unboxed_region.start_addr = page_address(0);
@@ -6044,7 +5866,9 @@ gc_init(void)
 
     bytes_allocated = 0;
 
-    /* Initialize the generations. */
+    /* Initialize the generations.
+     *
+     * FIXME: very similar to code in gc_free_heap(), should be shared */
     for (i = 0; i < NUM_GENERATIONS; i++) {
        generations[i].alloc_start_page = 0;
        generations[i].alloc_unboxed_start_page = 0;
@@ -6060,14 +5884,15 @@ gc_init(void)
        generations[i].min_av_mem_age = 0.75;
     }
 
-    /* Initialize gc_alloc. */
+    /* Initialize gc_alloc.
+     *
+     * FIXME: identical with code in gc_free_heap(), should be shared */
     gc_alloc_generation = 0;
     boxed_region.first_page = 0;
     boxed_region.last_page = -1;
     boxed_region.start_addr = page_address(0);
     boxed_region.free_pointer = page_address(0);
     boxed_region.end_addr = page_address(0);
-
     unboxed_region.first_page = 0;
     unboxed_region.last_page = -1;
     unboxed_region.start_addr = page_address(0);
@@ -6192,7 +6017,7 @@ alloc(int nbytes)
            SetSymbolValue(PSEUDO_ATOMIC_ATOMIC, make_fixnum(1));
            goto retry1;
        }
-       /* Call gc_alloc. */
+       /* Call gc_alloc(). */
        boxed_region.free_pointer = current_region_free_pointer;
        {
            void *new_obj = gc_alloc(nbytes);
@@ -6207,7 +6032,7 @@ alloc(int nbytes)
 
     retry2:
        /* At least wrap this allocation in a pseudo atomic to prevent
-        * gc_alloc from being re-entered. */
+        * gc_alloc() from being re-entered. */
        SetSymbolValue(PSEUDO_ATOMIC_INTERRUPTED, make_fixnum(0));
        SetSymbolValue(PSEUDO_ATOMIC_ATOMIC, make_fixnum(1));
 
@@ -6252,7 +6077,7 @@ alloc(int nbytes)
            goto retry2;
        }
 
-       /* Else call gc_alloc. */
+       /* Else call gc_alloc(). */
        boxed_region.free_pointer = current_region_free_pointer;
        result = gc_alloc(nbytes);
        current_region_free_pointer = boxed_region.free_pointer;
@@ -6261,8 +6086,7 @@ alloc(int nbytes)
        alloc_entered--;
        SetSymbolValue(PSEUDO_ATOMIC_ATOMIC, make_fixnum(0));
        if (SymbolValue(PSEUDO_ATOMIC_INTERRUPTED) != 0) {
-           /* Handle any interrupts that occurred during
-            * gc_alloc(..). */
+           /* Handle any interrupts that occurred during gc_alloc(..). */
            do_pending_interrupt();
            goto retry2;
        }
@@ -6287,21 +6111,23 @@ clear_auto_gc_trigger(void)
     auto_gc_trigger = 0;
 }
 \f
-/* Find the code object for the given pc, or return NULL on failure. */
-lispobj*
+/* Find the code object for the given pc, or return NULL on failure.
+ *
+ * FIXME: PC shouldn't be lispobj*, should it? Maybe void*? */
+lispobj *
 component_ptr_from_pc(lispobj *pc)
 {
     lispobj *object = NULL;
 
-    if (object = search_read_only_space(pc))
+    if ( (object = search_read_only_space(pc)) )
        ;
-    else if (object = search_static_space(pc))
+    else if ( (object = search_static_space(pc)) )
        ;
     else
        object = search_dynamic_space(pc);
 
     if (object) /* if we found something */
-       if (TypeOf(*object) == type_CodeHeader) /* if it's a code object */
+       if (widetag_of(*object) == CODE_HEADER_WIDETAG) /* if it's a code object */
            return(object);
 
     return (NULL);
@@ -6312,6 +6138,8 @@ component_ptr_from_pc(lispobj *pc)
  * catch GENCGC-related write-protect violations
  */
 
+void unhandled_sigmemoryfault(void);
+
 /* Depending on which OS we're running under, different signals might
  * be raised for a violation of write protection in the heap. This
  * function factors out the common generational GC magic which needs
@@ -6334,6 +6162,10 @@ gencgc_handle_wp_violation(void* fault_addr)
     /* Check whether the fault is within the dynamic space. */
     if (page_index == (-1)) {
 
+       /* It can be helpful to be able to put a breakpoint on this
+        * case to help diagnose low-level problems. */
+       unhandled_sigmemoryfault();
+
        /* not within the dynamic space -- not our responsibility */
        return 0;
 
@@ -6354,3 +6186,11 @@ gencgc_handle_wp_violation(void* fault_addr)
        return 1;
     }
 }
+
+/* This is to be called when we catch a SIGSEGV/SIGBUS, determine that
+ * it's not just a case of the program hitting the write barrier, and
+ * are about to let Lisp deal with it. It's basically just a
+ * convenient place to set a gdb breakpoint. */
+void
+unhandled_sigmemoryfault()
+{}