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))))))
+
 
 
 ;;; {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;
 
 
 
 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);