Use __builtin_unwind_init if available

* configure.in: Check for __builtin_unwind_init.

* src/alloc.c (mark_stack): Use __builtin_unwind_init if available.

1 files changed, 17 insertions, 4 deletions

diff --git a/src/alloc.c b/src/alloc.c
index e754e2f6aa2..089a7766ca4 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -1,6 +1,6 @@
 /* Storage allocation and gc for GNU Emacs Lisp interpreter.
    Copyright (C) 1985, 1986, 1988, 1993, 1994, 1995, 1997, 1998, 1999,
-      2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
+      2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011
       Free Software Foundation, Inc.
 
 This file is part of GNU Emacs.
@@ -4222,7 +4222,7 @@ Please mail the result to <emacs-devel@gnu.org>.\n\
    can prove that.  */
 
 static void
-test_setjmp ()
+test_setjmp (void)
 {
   char buf[10];
   register int x;
@@ -4270,7 +4270,7 @@ test_setjmp ()
 /* Abort if anything GCPRO'd doesn't survive the GC.  */
 
 static void
-check_gcpros ()
+check_gcpros (void)
 {
   struct gcpro *p;
   int i;
@@ -4286,7 +4286,7 @@ check_gcpros ()
 #elif GC_MARK_STACK == GC_USE_GCPROS_CHECK_ZOMBIES
 
 static void
-dump_zombies ()
+dump_zombies (void)
 {
   int i;
 
@@ -4321,6 +4321,11 @@ dump_zombies ()
    have to be true!  It must be verified for each system, possibly
    by taking a look at the source code of setjmp.
 
+   If __builtin_unwind_init is available (defined by GCC >= 2.8) we
+   can use it as a machine independent method to store all registers
+   to the stack.  In this case the macros described in the previous
+   two paragraphs are not used.
+
    Stack Layout
 
    Architectures differ in the way their processor stack is organized.
@@ -4359,6 +4364,13 @@ mark_stack (void)
   volatile int stack_grows_down_p = (char *) &j > (char *) stack_base;
   void *end;
 
+#ifdef HAVE___BUILTIN_UNWIND_INIT
+  /* Force callee-saved registers and register windows onto the stack.
+     This is the preferred method if available, obviating the need for
+     machine dependent methods.  */
+  __builtin_unwind_init ();
+  end = &end;
+#else /* not HAVE___BUILTIN_UNWIND_INIT */
   /* This trick flushes the register windows so that all the state of
      the process is contained in the stack.  */
   /* Fixme: Code in the Boehm GC suggests flushing (with `flushrs') is
@@ -4394,6 +4406,7 @@ mark_stack (void)
   setjmp (j.j);
   end = stack_grows_down_p ? (char *) &j + sizeof j : (char *) &j;
 #endif /* not GC_SAVE_REGISTERS_ON_STACK */
+#endif /* not HAVE___BUILTIN_UNWIND_INIT */
 
   /* 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