Re: stack overflow

[Neil Jerram <neil@ossau.uklinux.net>]

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"Mikael Djurfeldt" <mikael@djurfeldt.com> writes:

> I was thinking about inserting code which actually *measures* the size
> of frames during startup.  This could be done, for example, by
> introducing a primitive which uses the internal stack measuring
> functions.  One could use this primitive to measure how much stack
> space some code sample uses.  By our knowledge of how many evaluator
> stack frames this code sample uses, we can compute a reliable estimate
> for the running instance of Guile.

Below is a proposed patch to do this.  When and if this gets deployed,
the third arg to %calibrate-stack-depth would be removed, so that it
doesn't generate any output.  But for now it's interesting to see what
results people on various OSs get.

Could people who've being getting "Stack overflow" errors try this
out, and also report (for interest) the ";; Stack calibration" line
that they get?

Thanks,
     Neil



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Index: ice-9/boot-9.scm
===================================================================
RCS file: /cvsroot/guile/guile/guile-core/ice-9/boot-9.scm,v
retrieving revision 1.356.2.10
diff -u -r1.356.2.10 boot-9.scm
--- ice-9/boot-9.scm	1 Sep 2007 17:11:00 -0000	1.356.2.10
+++ ice-9/boot-9.scm	25 Feb 2008 21:45:44 -0000
@@ -2289,6 +2289,14 @@
    (print-options print-enable print-disable)
    (print-set!)))
 
+;;; Stack depth calibration, for the 'stack debug option.
+
+(let ((x (%get-stack-depth)))
+  (let loop ((count 10))
+    (if (zero? count)
+	(%calibrate-stack-depth x (%get-stack-depth) 'report)
+	(cons count (loop (- count 1))))))
+
 \f
 
 ;;; {Running Repls}
Index: libguile/debug.h
===================================================================
RCS file: /cvsroot/guile/guile/guile-core/libguile/debug.h,v
retrieving revision 1.58
diff -u -r1.58 debug.h
--- libguile/debug.h	4 Nov 2005 21:20:24 -0000	1.58
+++ libguile/debug.h	25 Feb 2008 21:45:44 -0000
@@ -75,6 +75,7 @@
     && scm_is_true (SCM_EXIT_FRAME_HDLR);\
   scm_debug_mode_p = SCM_DEVAL_P\
     || scm_check_entry_p || scm_check_apply_p || scm_check_exit_p;\
+  scm_calculate_stack_limit ();\
 } while (0)
 
 /* {Evaluator}
Index: libguile/stackchk.c
===================================================================
RCS file: /cvsroot/guile/guile/guile-core/libguile/stackchk.c,v
retrieving revision 1.28.2.1
diff -u -r1.28.2.1 stackchk.c
--- libguile/stackchk.c	12 Feb 2006 13:42:51 -0000	1.28.2.1
+++ libguile/stackchk.c	25 Feb 2008 21:45:44 -0000
@@ -30,6 +30,13 @@
 
 #ifdef STACK_CHECKING
 int scm_stack_checking_enabled_p;
+int scm_stack_limit;
+
+/* As in y = mx + c.  These numbers define a linear transformation
+   from the stack depth specified as the 'stack debug option, to the
+   actual max stack depth that we allow. */
+static double calibrated_m = 1;
+static double calibrated_c = 0;
 
 SCM_SYMBOL (scm_stack_overflow_key, "stack-overflow");
 
@@ -44,6 +51,58 @@
 	     SCM_BOOL_F);
 }
 
+/* Stack depth calibration. */
+
+SCM_DEFINE (scm_sys_get_stack_depth, "%get-stack-depth", 0, 0, 0,
+	    (),
+	    "Return current stack depth.")
+#define FUNC_NAME s_scm_sys_get_stack_depth
+{
+  SCM_STACKITEM stack;
+  return scm_from_int (SCM_STACK_DEPTH (&stack));
+}
+#undef FUNC_NAME
+
+SCM_DEFINE (scm_sys_calibrate_stack_depth, "%calibrate-stack-depth", 2, 1, 0,
+	    (SCM d1, SCM d2, SCM debugp),
+	    "Calibrate linear transformation for stack depth limit checking.")
+#define FUNC_NAME s_scm_sys_calibrate_stack_depth
+{
+  /* x1 and x2 are the stack depth values that we get on a Debian
+     GNU/Linux ia32 system - which we take as our canonical system.
+     y1 and y2 are the values measured on the system where Guile is
+     currently running. */
+  int x1 = 170, x2 = 690, y1, y2;
+
+  SCM_VALIDATE_INT_COPY (1, d1, y1);
+  SCM_VALIDATE_INT_COPY (2, d2, y2);
+
+  calibrated_m = ((double) (y2 - y1)) / (x2 - x1);
+  calibrated_c = ((double) y2) - calibrated_m * x2;
+
+  if (scm_is_true (debugp) && !SCM_UNBNDP (debugp))
+    {
+      scm_puts (";; Stack calibration: (x1 x2 y1 y2 m c) = ",
+		scm_current_output_port ());
+      scm_write (scm_list_n (scm_from_int (x1), scm_from_int (x2),
+			     d1, d2,
+			     scm_from_double (calibrated_m),
+			     scm_from_double (calibrated_c),
+			     SCM_UNDEFINED),
+		 SCM_UNDEFINED);
+      scm_newline (SCM_UNDEFINED);
+    }
+
+  return SCM_UNSPECIFIED;
+}
+#undef FUNC_NAME
+
+void
+scm_calculate_stack_limit ()
+{
+  scm_stack_limit = (int) (calibrated_m * SCM_STACK_LIMIT + calibrated_c);
+}
+
 #endif
 
 long
Index: libguile/stackchk.h
===================================================================
RCS file: /cvsroot/guile/guile/guile-core/libguile/stackchk.h,v
retrieving revision 1.20.2.1
diff -u -r1.20.2.1 stackchk.h
--- libguile/stackchk.h	12 Feb 2006 13:42:51 -0000	1.20.2.1
+++ libguile/stackchk.h	25 Feb 2008 21:45:44 -0000
@@ -35,14 +35,11 @@
 
 #ifdef STACK_CHECKING
 # if SCM_STACK_GROWS_UP
-#  define SCM_STACK_OVERFLOW_P(s)\
-   (SCM_STACK_PTR (s) \
-    > (SCM_I_CURRENT_THREAD->base + SCM_STACK_LIMIT))
+#  define SCM_STACK_DEPTH(s) (SCM_STACK_PTR (s) - SCM_I_CURRENT_THREAD->base)
 # else
-#  define SCM_STACK_OVERFLOW_P(s)\
-   (SCM_STACK_PTR (s) \
-    < (SCM_I_CURRENT_THREAD->base - SCM_STACK_LIMIT))
+#  define SCM_STACK_DEPTH(s) (SCM_I_CURRENT_THREAD->base - SCM_STACK_PTR (s))
 # endif
+# define SCM_STACK_OVERFLOW_P(s) (SCM_STACK_DEPTH (s) > scm_stack_limit)
 # define SCM_CHECK_STACK\
     {\
        SCM_STACKITEM stack;\
@@ -54,10 +51,14 @@
 #endif /* STACK_CHECKING */
 
 SCM_API int scm_stack_checking_enabled_p;
+SCM_API int scm_stack_limit;
 
 \f
 
 SCM_API void scm_report_stack_overflow (void);
+SCM_API SCM scm_sys_get_stack_depth (void);
+SCM_API SCM scm_sys_calibrate_stack_depth (SCM d1, SCM d2, SCM debugp);
+SCM_API void scm_calculate_stack_limit (void);
 SCM_API long scm_stack_size (SCM_STACKITEM *start);
 SCM_API void scm_stack_report (void);
 SCM_API void scm_init_stackchk (void);