Give more-useful info on a fatal error (Bug#12328).

* doc/emacs/trouble.texi (Crashing): New section, documenting this.
* etc/NEWS: Document the change.
* src/alloc.c [ENABLE_CHECKING]: Do not include <execinfo.h>.
(die) [ENABLE_CHECKING]: Call fatal_error_backtrace instead
of doing the work ourselves.
* src/emacs.c (fatal_error_signal): Let fatal_error_backtrace
do most of the work.
(fatal_error_backtrace): New function, taken from the guts
of the old fatal_error_signal, but with a new option to output
a backtrace.
(shut_down_emacs) [!DOS_NT]: Use strsignal to give more-useful
info about the signal than just its number.
* src/lisp.h (fatal_error_backtrace, emacs_backtrace): New decls.
* src/sysdep.c: Include <execinfo.h>
(emacs_backtrace): New function, taken partly from the previous
code of the 'die' function.
(emacs_abort): Call fatal_error_backtrace rather than abort.

2 files changed, 10 insertions, 0 deletions

diff --git a/etc/ChangeLog b/etc/ChangeLog
index f3f244c7e39..aa788275256 100644
--- a/etc/ChangeLog
+++ b/etc/ChangeLog
@@ -1,3 +1,8 @@
+2012-09-04  Paul Eggert  <eggert@cs.ucla.edu>
+
+        Give more-useful info on a fatal error (Bug#12328).
+        * NEWS: Document the change.
+
 2012-09-01  Paul Eggert  <eggert@cs.ucla.edu>
 
         Better seeds for (random).
diff --git a/etc/NEWS b/etc/NEWS
index e4a612f6a9e..9a38deef05c 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -97,6 +97,11 @@ machines.  Other functions that use this format, such as
 file-attributes and format-time-string, have been changed accordingly.
 Old-format time stamps are still accepted.
 
+** Emacs now generates backtraces on fatal errors.
+On encountering a fatal error, Emacs now outputs a textual description
+of the fatal signal, and a short backtrace on platforms like glibc
+that support backtraces.
+
 ** New functions `system-users', `system-groups' return lists of the user
 name, group names known to the system (where possible).