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.

3 files changed, 17 insertions, 0 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 95b9a57f24b..fbaf555f8b2 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,11 @@
 2012-08-25  Paul Eggert  <eggert@cs.ucla.edu>
 
+        On assertion failure, print backtrace if available.
+        * alloc.c [ENABLE_CHECKING]: Include <execinfo.h>.
+        (die) [ENABLE_CHECKING]: Print a backtrace if available.
+        * Makefile.in (LIB_EXECINFO): New macro.
+        (LIBES): Use it.
+
         * bytecode.c, callint.c, callproc.c: Use bool for boolean.
         * bytecode.c (exec_byte_code):
         * callint.c (check_mark, Fcall_interactively):
diff --git a/src/Makefile.in b/src/Makefile.in
index 1d89af31401..85645222052 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -159,6 +159,8 @@ DBUS_LIBS = @DBUS_LIBS@
 ## dbusbind.o if HAVE_DBUS, else empty.
 DBUS_OBJ = @DBUS_OBJ@
 
+LIB_EXECINFO=@LIB_EXECINFO@
+
 SETTINGS_CFLAGS = @SETTINGS_CFLAGS@
 SETTINGS_LIBS = @SETTINGS_LIBS@
 
@@ -383,6 +385,7 @@ otherobj= $(TERMCAP_OBJ) $(PRE_ALLOC_OBJ) $(GMALLOC_OBJ) $(RALLOC_OBJ) \
 ## with GCC, we might need LIB_GCC again after them.
 LIBES = $(LIBS) $(LIBX_BASE) $(LIBX_OTHER) $(LIBSOUND) \
    $(RSVG_LIBS) $(IMAGEMAGICK_LIBS) $(LIB_CLOCK_GETTIME) $(DBUS_LIBS) \
+   $(LIB_EXECINFO) \
    $(LIBXML2_LIBS) $(LIBGPM) $(LIBRESOLV) $(LIBS_SYSTEM) \
    $(LIBS_TERMCAP) $(GETLOADAVG_LIBS) $(SETTINGS_LIBS) $(LIBSELINUX_LIBS) \
    $(FREETYPE_LIBS) $(FONTCONFIG_LIBS) $(LIBOTF_LIBS) $(M17N_FLT_LIBS) \
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