C backtraces for Emacs

[Paul Eggert]

On 08/21/2012 10:50 AM, Stefan Monnier wrote:
> If someone wants to *additionally* provide a patch to use glibc's
> `backtrace' in our `eassert' that's fine

I've prepared a patch to do this additional work, enclosed below.  The
key part is at the end; the rest is boilerplate for non-GNUish
systems.  I've tested this on Fedora 15, Solaris 11, and Solaris 10.

I'll hold off installing this to give Eli and Juanma a heads-up, as it
creates a new substitute header <execinfo.h> on non-GNUish systems,
and the Windows build will need to do something similar.  If I understand
things correctly Windows already does backtraces in a different way, so
its execinfo.h can just be a copy of execinfo.in.h.

=== modified file 'ChangeLog'
--- ChangeLog   2012-08-22 06:55:44 +0000
+++ ChangeLog   2012-08-22 08:59:10 +0000
@@ -1,3 +1,11 @@
+2012-08-22  Paul Eggert  <address@hidden>
+
+       On assertion failure, print backtrace if available.
+       Merge from gnulib, incorporating:
+       2012-08-22 execinfo: new module
+       * lib/gnulib.mk, m4/gnulib-comp.m4: Regenerate.
+       * lib/execinfo.c, lib/execinfo.in.h, m4/execinfo.m4: New files.
+
 2012-08-22  Glenn Morris  <address@hidden>
 
        * Makefile.in (install-arch-dep): If NO_BIN_LINK is non-null,

=== modified file 'admin/ChangeLog'
--- admin/ChangeLog     2012-08-16 21:58:44 +0000
+++ admin/ChangeLog     2012-08-22 08:59:10 +0000
@@ -1,3 +1,8 @@
+2012-08-22  Paul Eggert  <address@hidden>
+
+       On assertion failure, print backtrace if available.
+       * merge-gnulib (GNULIB_MODULES): Add execinfo.
+
 2012-08-16  Paul Eggert  <address@hidden>
 
        Use ASCII tests for character types.

=== modified file 'admin/merge-gnulib'
--- admin/merge-gnulib  2012-08-16 21:58:44 +0000
+++ admin/merge-gnulib  2012-08-22 08:59:10 +0000
@@ -28,7 +28,7 @@
 GNULIB_MODULES='
   alloca-opt c-ctype c-strcase
   careadlinkat crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512
-  dtoastr dtotimespec dup2 environ
+  dtoastr dtotimespec dup2 environ execinfo
   filemode getloadavg getopt-gnu gettime gettimeofday
   ignore-value intprops largefile lstat
   manywarnings mktime pselect pthread_sigmask readlink

=== added file 'lib/execinfo.c'
--- lib/execinfo.c      1970-01-01 00:00:00 +0000
+++ lib/execinfo.c      2012-08-22 08:59:10 +0000
@@ -0,0 +1,3 @@
+#include <config.h>
+#define _GL_EXECINFO_INLINE _GL_EXTERN_INLINE
+#include "execinfo.h"

=== added file 'lib/execinfo.in.h'
--- lib/execinfo.in.h   1970-01-01 00:00:00 +0000
+++ lib/execinfo.in.h   2012-08-22 08:59:10 +0000
@@ -0,0 +1,54 @@
+/* Information about executables.
+
+   Copyright (C) 2012 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* Written by Paul Eggert.  */
+
+#ifndef _GL_EXECINFO_H
+#define _GL_EXECINFO_H
+
+_GL_INLINE_HEADER_BEGIN
+#ifndef _GL_EXECINFO_INLINE
+# define _GL_EXECINFO_INLINE _GL_INLINE
+#endif
+
+_GL_EXECINFO_INLINE int
+backtrace (void **buffer, int size)
+{
+  (void) buffer;
+  (void) size;
+  return 0;
+}
+
+_GL_EXECINFO_INLINE char **
+backtrace_symbols (void *const *buffer, int size)
+{
+  (void) buffer;
+  (void) size;
+  return 0;
+}
+
+_GL_EXECINFO_INLINE void
+backtrace_symbols_fd (void *const *buffer, int size, int fd)
+{
+  (void) buffer;
+  (void) size;
+  (void) fd;
+}
+
+_GL_INLINE_HEADER_END
+
+#endif

=== modified file 'lib/gnulib.mk'
--- lib/gnulib.mk       2012-08-19 23:31:24 +0000
+++ lib/gnulib.mk       2012-08-22 08:59:10 +0000
@@ -21,7 +21,7 @@
 # the same distribution terms as the rest of that program.
 #
 # Generated by gnulib-tool.
-# Reproduce by: gnulib-tool --import --dir=. --lib=libgnu --source-base=lib 
--m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux 
--avoid=errno --avoid=fcntl --avoid=fcntl-h --avoid=fstat --avoid=msvc-inval 
--avoid=msvc-nothrow --avoid=raise --avoid=select --avoid=sigprocmask 
--avoid=sys_types --avoid=threadlib --makefile-name=gnulib.mk 
--conditional-dependencies --no-libtool --macro-prefix=gl --no-vc-files 
alloca-opt c-ctype c-strcase careadlinkat crypto/md5 crypto/sha1 crypto/sha256 
crypto/sha512 dtoastr dtotimespec dup2 environ filemode getloadavg getopt-gnu 
gettime gettimeofday ignore-value intprops largefile lstat manywarnings mktime 
pselect pthread_sigmask readlink socklen stat-time stdalign stdarg stdbool 
stdio strftime strtoimax strtoumax symlink sys_stat sys_time time timespec-add 
timespec-sub utimens warnings
+# Reproduce by: gnulib-tool --import --dir=. --lib=libgnu --source-base=lib 
--m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux 
--avoid=errno --avoid=fcntl --avoid=fcntl-h --avoid=fstat --avoid=msvc-inval 
--avoid=msvc-nothrow --avoid=raise --avoid=select --avoid=sigprocmask 
--avoid=sys_types --avoid=threadlib --makefile-name=gnulib.mk 
--conditional-dependencies --no-libtool --macro-prefix=gl --no-vc-files 
alloca-opt c-ctype c-strcase careadlinkat crypto/md5 crypto/sha1 crypto/sha256 
crypto/sha512 dtoastr dtotimespec dup2 environ execinfo filemode getloadavg 
getopt-gnu gettime gettimeofday ignore-value intprops largefile lstat 
manywarnings mktime pselect pthread_sigmask readlink socklen stat-time stdalign 
stdarg stdbool stdio strftime strtoimax strtoumax symlink sys_stat sys_time 
time timespec-add timespec-sub utimens warnings
 
 
 MOSTLYCLEANFILES += core *.stackdump
@@ -150,6 +150,31 @@
 
 ## end   gnulib module dup2
 
+## begin gnulib module execinfo
+
+BUILT_SOURCES += $(EXECINFO_H)
+
+# We need the following in order to create <execinfo.h> when the system
+# doesn't have one that works.
+if GL_GENERATE_EXECINFO_H
+execinfo.h: execinfo.in.h $(top_builddir)/config.status
+       $(AM_V_GEN)rm -f address@hidden $@ && \
+       { echo '/* DO NOT EDIT! GENERATED AUTOMATICALLY! */'; \
+         cat $(srcdir)/execinfo.in.h; \
+       } > address@hidden && \
+       mv address@hidden $@
+else
+execinfo.h: $(top_builddir)/config.status
+       rm -f $@
+endif
+MOSTLYCLEANFILES += execinfo.h execinfo.h-t
+
+EXTRA_DIST += execinfo.c execinfo.in.h
+
+EXTRA_libgnu_a_SOURCES += execinfo.c
+
+## end   gnulib module execinfo
+
 ## begin gnulib module filemode
 
 libgnu_a_SOURCES += filemode.c

=== added file 'm4/execinfo.m4'
--- m4/execinfo.m4      1970-01-01 00:00:00 +0000
+++ m4/execinfo.m4      2012-08-22 08:59:10 +0000
@@ -0,0 +1,21 @@
+# Check for GNU-style execinfo.h.
+
+dnl Copyright 2012 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_EXECINFO_H],
+[
+  AC_CHECK_HEADERS_ONCE([execinfo.h])
+
+  if test $ac_cv_header_execinfo_h = yes; then
+    EXECINFO_H=''
+  else
+    EXECINFO_H='execinfo.h'
+    AC_LIBOBJ([execinfo])
+  fi
+
+  AC_SUBST([EXECINFO_H])
+  AM_CONDITIONAL([GL_GENERATE_EXECINFO_H], [test -n "$EXECINFO_H"])
+])

=== modified file 'm4/gnulib-comp.m4'
--- m4/gnulib-comp.m4   2012-08-19 23:31:24 +0000
+++ m4/gnulib-comp.m4   2012-08-22 08:59:10 +0000
@@ -53,6 +53,7 @@
   # Code from module dtotimespec:
   # Code from module dup2:
   # Code from module environ:
+  # Code from module execinfo:
   # Code from module extensions:
   AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
   # Code from module extern-inline:
@@ -152,6 +153,7 @@
   gl_UNISTD_MODULE_INDICATOR([dup2])
   gl_ENVIRON
   gl_UNISTD_MODULE_INDICATOR([environ])
+  gl_EXECINFO_H
   AC_REQUIRE([gl_EXTERN_INLINE])
   gl_FILEMODE
   gl_GETLOADAVG
@@ -534,6 +536,8 @@
   lib/dtoastr.c
   lib/dtotimespec.c
   lib/dup2.c
+  lib/execinfo.c
+  lib/execinfo.in.h
   lib/filemode.c
   lib/filemode.h
   lib/ftoastr.c
@@ -605,6 +609,7 @@
   m4/clock_time.m4
   m4/dup2.m4
   m4/environ.m4
+  m4/execinfo.m4
   m4/extensions.m4
   m4/extern-inline.m4
   m4/filemode.m4

=== modified file 'src/ChangeLog'
--- src/ChangeLog       2012-08-22 07:20:42 +0000
+++ src/ChangeLog       2012-08-22 08:59:10 +0000
@@ -1,5 +1,9 @@
 2012-08-22  Paul Eggert  <address@hidden>
 
+       On assertion failure, print backtrace if available.
+       * alloc.c [ENABLE_CHECKING]: Include <execinfo.h>.
+       (die) [ENABLE_CHECKING]: Print a backtrace if available.
+
        * fontset.c (FONTSET_ADD): Return void, not Lisp_Object.
        Otherwise, the compiler complains about (A?B:C) where B is void
        and C is Lisp_Object.  This fixes an incompatibility with Sun C 5.12.

=== modified file 'src/alloc.c'
--- src/alloc.c 2012-08-21 23:39:56 +0000
+++ src/alloc.c 2012-08-22 08:59:10 +0000
@@ -6681,13 +6681,21 @@
 }
 
 #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