Re: Avoid C stack overflow

[Dmitry Antipov]

On 03/14/2014 10:59 AM, Paul Eggert wrote:

> Good point, I forgot about the stack-scanning problem.

After reading http://gcc.gnu.org/wiki/SplitStacks and
looking into libgcc sources, this looks reasonably simple:

=== modified file 'src/alloc.c'
--- src/alloc.c 2014-02-28 21:45:34 +0000
+++ src/alloc.c 2014-03-14 11:17:42 +0000
@@ -4866,11 +4866,30 @@
 #endif /* not GC_SAVE_REGISTERS_ON_STACK */
 #endif /* not HAVE___BUILTIN_UNWIND_INIT */

+#ifdef SPLIT_STACK
+
+  /* This assumes gcc >= 4.6.0 with -fsplit-stack
+     and corresponding support in libgcc.  */
+  {
+    size_t stack_size;
+    extern void * __splitstack_find (void *, void *, size_t *,
+                                    void **, void **, void **);
+    void *next_segment = NULL, *next_sp = NULL, *initial_sp = NULL, *stack;
+
+    while ((stack = __splitstack_find (next_segment, next_sp, &stack_size,
+                                      &next_segment, &next_sp, &initial_sp)))
+      mark_memory (stack, (char *) stack + stack_size);
+  }
+
+#else /* not SPLIT_STACK */
+
   /* This assumes that the stack is a contiguous region in memory.  If
      that's not the case, something has to be done here to iterate
      over the stack segments.  */
   mark_memory (stack_base, end);

+#endif /* SPLIT_STACK */
+
   /* Allow for marking a secondary stack, like the register stack on the
      ia64.  */
 #ifdef GC_MARK_SECONDARY_STACK

After compiling with CPPFLAGS='-DSPLIT_STACK' and CFLAGS='-O0 -fsplit-stack 
-g3',
I even got the binary which doesn't crash immediately (but do it somewhat
later, after a long byte-compile run :-().

Dmitry