* alloc.c (garbage_collect): Don't assume stack size fits in int.

(stack_copy_size): Now size_t, not int.
(stack_copy, stack_copy_size): Define only if MAX_SAVE_STACK > 0.

2 files changed, 26 insertions, 13 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index cc40c863e97..cf9ca86a798 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,9 @@
+2011-03-26  Paul Eggert  <eggert@cs.ucla.edu>
+
+        * alloc.c (garbage_collect): Don't assume stack size fits in int.
+        (stack_copy_size): Now size_t, not int.
+        (stack_copy, stack_copy_size): Define only if MAX_SAVE_STACK > 0.
+
 2011-03-26  Juanma Barranquero  <lekktu@gmail.com>
 
         * w32.c (read_unc_volume): Use parameter `henum', instead of
diff --git a/src/alloc.c b/src/alloc.c
index 66695e7a9bc..00f053e9090 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -254,8 +254,10 @@ const char *pending_malloc_warning;
 
 /* Buffer in which we save a copy of the C stack at each GC.  */
 
+#if MAX_SAVE_STACK > 0
 static char *stack_copy;
-static int stack_copy_size;
+static size_t stack_copy_size;
+#endif
 
 /* Non-zero means ignore malloc warnings.  Set during initialization.
    Currently not used.  */
@@ -4903,21 +4905,26 @@ returns nil, because real GC can't be done.  */)
 #if MAX_SAVE_STACK > 0
   if (NILP (Vpurify_flag))
     {
-      i = &stack_top_variable - stack_bottom;
-      if (i < 0) i = -i;
-      if (i < MAX_SAVE_STACK)
+      char *stack;
+      size_t stack_size;
+      if (&stack_top_variable < stack_bottom)
+        {
+          stack = &stack_top_variable;
+          stack_size = stack_bottom - &stack_top_variable;
+        }
+      else
+        {
+          stack = stack_bottom;
+          stack_size = &stack_top_variable - stack_bottom;
+        }
+      if (stack_size <= MAX_SAVE_STACK)
         {
-          if (stack_copy == 0)
-            stack_copy = (char *) xmalloc (stack_copy_size = i);
-          else if (stack_copy_size < i)
-            stack_copy = (char *) xrealloc (stack_copy, (stack_copy_size = i));
-          if (stack_copy)
+          if (stack_copy_size < stack_size)
             {
-              if ((EMACS_INT) (&stack_top_variable - stack_bottom) > 0)
-                memcpy (stack_copy, stack_bottom, i);
-              else
-                memcpy (stack_copy, &stack_top_variable, i);
+              stack_copy = (char *) xrealloc (stack_copy, stack_size);
+              stack_copy_size = stack_size;
             }
+          memcpy (stack_copy, stack, stack_size);
         }
     }
 #endif /* MAX_SAVE_STACK > 0 */