On assertion failure, print backtrace if available.

Merge from gnulib, incorporating:
2012-08-24 execinfo: port to FreeBSD
2012-08-22 execinfo: new module
* admin/merge-gnulib (GNULIB_MODULES): Add execinfo.
* lib/gnulib.mk, m4/gnulib-comp.m4: Regenerate.
* lib/execinfo.c, lib/execinfo.in.h, m4/execinfo.m4: New files.
* src/alloc.c [ENABLE_CHECKING]: Include <execinfo.h>.
(die) [ENABLE_CHECKING]: Print a backtrace if available.
* src/Makefile.in (LIB_EXECINFO): New macro.
(LIBES): Use it.

1 files changed, 8 insertions, 0 deletions

diff --git a/src/alloc.c b/src/alloc.c
index f0da9416ece..961febb6dff 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -6681,13 +6681,21 @@ which_symbols (Lisp_Object obj, EMACS_INT find_max)
 }
 
 #ifdef ENABLE_CHECKING
+
+# include <execinfo.h>
+
 bool suppress_checking;
 
 void
 die (const char *msg, const char *file, int line)
 {
+  enum { NPOINTERS_MAX = 500 };
+  void *buffer[NPOINTERS_MAX];
+  int npointers;
   fprintf (stderr, "\r\n%s:%d: Emacs fatal error: %s\r\n",
            file, line, msg);
+  npointers = backtrace (buffer, NPOINTERS_MAX);
+  backtrace_symbols_fd (buffer, npointers, STDERR_FILENO);
   abort ();
 }
 #endif