X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=src%2Fcode%2Fexhaust.lisp;h=25c038e0920434a4988ef72ffaff6421fe5d777f;hb=409c08485fd358c78107d91f9e3aec4d17b3fd0d;hp=67f5a38f9136f8bc0ec53ad49a31ac93295c62d3;hpb=8286d1fc02d1e769a766fbf1670bca474237161f;p=sbcl.git

diff --git a/src/code/exhaust.lisp b/src/code/exhaust.lisp
index 67f5a38..25c038e 100644
--- a/src/code/exhaust.lisp
+++ b/src/code/exhaust.lisp
@@ -1,4 +1,5 @@
-;;;; detecting and handling exhaustion of memory (stack or heap)
+;;;; detecting and handling exhaustion of fundamental system resources
+;;;; (stack or heap)
 
 ;;;; This software is part of the SBCL system. See the README file for
 ;;;; more information.
@@ -11,59 +12,62 @@
 
 (in-package "SB!KERNEL")
 
-;;; A native address on a 4-byte boundary can be thought of (and
-;;; passed around in Lisp code as) a FIXNUM. This function converts
-;;; from a byte address represented as an unsigned integer to such
-;;; a FIXNUM.
+;;; a soft limit on control stack overflow; the boundary beyond which
+;;; the control stack will be considered to've overflowed
 ;;;
-;;; FIXME: There should be some better place for this definition to
-;;; go. (Or a redundant definition might already exist. Especially
-;;; since this is essentially just a type pun, so there might be some
-;;; VOP or something which'd do it for us.)
-(eval-when (:compile-toplevel :load-toplevel :execute)
-  (defun native-address-encoded-as-fixnum (native-address)
-    (declare (type unsigned-byte native-address))
-    (aver (zerop (logand native-address 3)))
-    (let* (;; naive encoding
-	   (first-try (ash native-address -2))
-	   ;; final encoding
-	   (second-try 
-	    (if (<= first-try sb!vm:*target-most-positive-fixnum*)
-		;; looks good
-		first-try
-		;; When the naive encoding fails to make a FIXNUM
-		;; because the sign is wrong, subtracting *T-M-P-F*
-		;; should fix it. 
-		(- first-try sb!vm:*target-most-positive-fixnum*))))
-      (aver (<= second-try sb!vm:*target-most-positive-fixnum*))
-      second-try)))
-
-;;; a FIXNUM, to be interpreted as a native pointer, which serves
-;;; as a boundary to catch stack overflow
-;;;
-;;; When stack overflow is detected, this is to be bound to a new
-;;; value (allowing some more space for error handling) around the
-;;; call to ERROR.
+;;; When overflow is detected, this soft limit is to be bound to a new
+;;; value closer to the hard limit (allowing some more space for error
+;;; handling) around the call to ERROR, to allow space for the
+;;; error-handling logic.
 ;;;
 ;;; FIXME: Maybe (probably?) this should be in SB!VM. And maybe the
 ;;; size of the buffer zone should be set in src/compiler/cpu/parms.lisp
 ;;; instead of constantly 1Mb for all CPU architectures?
-(defvar *stack-exhaustion*
+(defvar *control-stack-exhaustion-sap*
   ;; (initialized in cold init)
   )
 (defun !exhaust-cold-init ()
-  (setf *stack-exhaustion*
-	#.(native-address-encoded-as-fixnum
-	   #!+stack-grows-downward (+ sb!vm:control-stack-start (expt 2 20))
-	   #!+stack-grows-upward (- sb!vm:control-stack-end (expt 2 20)))))
+  (let (;; initial difference between soft limit and hard limit
+	(initial-slack (expt 2 20)))
+    (setf *control-stack-exhaustion-sap*
+	  (int-sap #!+stack-grows-downward-not-upward
+		   (+ sb!vm:control-stack-start initial-slack)
+		   #!-stack-grows-downward-not-upward
+		   (- sb!vm:control-stack-end initial-slack)))))
   
 ;;; FIXME: Even though this is only called when (> SAFETY (MAX SPEED SPACE))
 ;;; it's still annoyingly wasteful for it to be a full function call.
 ;;; It should probably be a VOP calling an assembly routine or something
 ;;; like that.
 (defun %detect-stack-exhaustion ()
-  ;; FIXME: Check the stack pointer against *STACK-EXHAUSTION*, and if
-  ;; out of range signal an error (in a context where *S-E* has been
-  ;; rebound to give some space to let error handling code do its
-  ;; thing without new exhaustion problems).
-  (values))
+  (when (#!-stack-grows-downward-not-upward sap>=
+	 #!+stack-grows-downward-not-upward sap<=
+	 (current-sp)
+	 *control-stack-exhaustion-sap*)
+    (let ((*control-stack-exhaustion-sap*
+	   (revised-control-stack-exhaustion-sap)))
+      (warn "~@<ordinary control stack soft limit temporarily displaced to ~
+             allow possible interactive debugging~@:>")
+      (error "The system control stack was exhausted.")))
+  ;; FIXME: It'd be good to check other stacks (e.g. binding stack)
+  ;; here too.
+  )
+
+;;; Return a revised value for the *CONTROL-STACK-EXHAUSTION-SAP* soft
+;;; limit, allocating half the remaining space up to the hard limit in
+;;; order to allow interactive debugging to be used around the point
+;;; of a stack overflow failure without immediately failing again from
+;;; the (continuing) stack overflow.
+(defun revised-control-stack-exhaustion-sap ()
+  (let* ((old-slack
+	  #!-stack-grows-downward-not-upward
+	  (- sb!vm:control-stack-end
+	     (sap-int *control-stack-exhaustion-sap*))
+	  #!+stack-grows-downward-not-upward
+	  (- (sap-int *control-stack-exhaustion-sap*)
+	     sb!vm:control-stack-start))
+	 (new-slack (ash old-slack -1)))
+    (int-sap #!-stack-grows-downward-not-upward
+	     (- sb!vm:control-stack-end new-slack)
+	     #!+stack-grows-downward-not-upward
+	     (+ sb!vm:control-stack-start new-slack))))