X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=base-target-features.lisp-expr;h=519c5063333f38fc1ae92760bb6eaa1fc022b4ac;hb=2e91e29892268b2c7e5ab557e8192fa03bce68f2;hp=7bed4b77fa3038d0e24d2c6a307c221e11f43958;hpb=4eb1a6d3ad2b7dcc19ac0ec979a1eb1eb049659a;p=sbcl.git

diff --git a/base-target-features.lisp-expr b/base-target-features.lisp-expr
index 7bed4b7..519c506 100644
--- a/base-target-features.lisp-expr
+++ b/base-target-features.lisp-expr
@@ -1,3 +1,5 @@
+;;;; -*- Lisp -*-
+
 ;;;; tags which are set during the build process and which end up in
 ;;;; CL:*FEATURES* in the target SBCL, plus some comments about other
 ;;;; CL:*FEATURES* tags which have special meaning to SBCL or which
@@ -40,13 +42,17 @@
  ;; our standard
  :ansi-cl :common-lisp
  ;; FIXME: Isn't there a :x3jsomething feature which we should set too?
+ ;; No. CLHS says ":x3j13 [...] A conforming implementation might or
+ ;; might not contain such a feature." -- CSR, 2002-02-21
 
  ;; our dialect
  :sbcl
 
  ;; Douglas Thomas Crosher's conservative generational GC (the only one
- ;; we currently support for X86)
- :gencgc
+ ;; we currently support for X86).
+ ;; :gencgc used to be here; CSR moved it into
+ ;; local-target-features.lisp-expr via make-config.sh, as alpha,
+ ;; sparc and ppc ports don't currently support it. -- CSR, 2002-02-21
 
  ;; We're running under a UNIX. This is sort of redundant, and it was also
  ;; sort of redundant under CMU CL, which we inherited it from: neither SBCL
@@ -102,14 +108,15 @@
 
  ;; Build SBCL with the old CMU CL low level debugger, "ldb". If 
  ;; are aren't messing with CMU CL at a very low level (e.g. 
- ;; trying to diagnose GC problems) you shouldn't need this.
+ ;; trying to diagnose GC problems, or trying to debug assembly
+ ;; code for a port to a new CPU) you shouldn't need this.
  ; :sb-ldb
 
  ;; This isn't really a target Lisp feature at all, but controls
  ;; whether the build process produces an after-xc.core file. This
- ;; can be useful for shortening the edit/compile/debug cycle if
- ;; you're messing around with low-level internals of the system,
- ;; as in slam.sh. Otherwise you don't need it.
+ ;; can be useful for shortening the edit/compile/debug cycle when
+ ;; you modify SBCL's own source code, as in slam.sh. Otherwise
+ ;; you don't need it.
  ; :sb-after-xc-core
 
  ;; Enable extra debugging output in the assem.lisp assembler/scheduler
@@ -241,6 +248,19 @@
  ;; documented in the CMU CL code that SBCL is derived from, and is
  ;; present but stale in SBCL as of 0.6.12.)
  ;;
+ ;; properties derived from the machine architecture
+ ;;   :control-stack-grows-downward-not-upward
+ ;;     On the X86, the Lisp control stack grows downward. On the
+ ;;     other supported CPU architectures as of sbcl-0.7.1.40, the
+ ;;     system stack grows upward. 
+ ;;   Note that there are other stack-related differences between the
+ ;;   X86 port and the other ports. E.g. on the X86, the Lisp control
+ ;;   stack coincides with the C stack, meaning that on the X86 there's
+ ;;   stuff on the control stack that the Lisp-level debugger doesn't
+ ;;   understand very well. As of sbcl-0.7.1.40 things like that are
+ ;;   just parameterized by #!+X86, but it'd probably be better to
+ ;;   use new flags like :CONTROL-STACK-CONTAINS-C-STACK.
+ ;;
  ;; operating system features:
  ;;   :linux   = We're intended to run under some version of Linux.
  ;;   :bsd     = We're intended to run under some version of BSD Unix. (This