Support storing assertion messages into core dump

Crash interception/debugging systems like Apport or ABRT capture core dumps for
later crash analysis. However, if a program exits with an assertion failure,
the core dump is not useful since the assertion message is only printed to
stderr.

glibc recently got a patch which stores the message of assert() into the
__abort_msg global variable.
(http://sourceware.org/git/?p=glibc.git;a=commitdiff;h=48dcd0ba)
That works fine for programs which actually use the standard C assert() macro.

This patch adds the same functionality for glib's assertion tests. If we are
building against a glibc which already has __abort_msg (2.11 and later, or
backported above git commit), use that, otherwise put it into our own field
__glib_assert_msg.

Usage:

  $ cat test.c
  #include <glib.h>

  int main() {
      g_assert(1 < 0);
      return 0;
  }

  $ ./test
  **ERROR:test.c:5:main: assertion failed: (1 < 0)
  Aborted (Core dumped)

  $ gdb --batch --ex 'print (char*) __abort_msg' ./test core
  [...]
  $1 = 0x93bf028 "ERROR:test.c:5:main: assertion failed: (1 < 0)"

https://bugzilla.gnome.org/show_bug.cgi?id=594872

configure.in

@@ -2676,6 +2676,20 @@ int error = EILSEQ;
 ], have_eilseq=yes, have_eilseq=no);
 AC_MSG_RESULT($have_eilseq)
 
+dnl **********************************************************************
+dnl *** Check whether glibc has global variable for assertion messages ***
+dnl **********************************************************************
+
+AC_MSG_CHECKING(if libc has __abort_msg)
+AC_LINK_IFELSE([
+extern char *__abort_msg;
+int main() { return __abort_msg == (char*) 0; }
+], [libc_has_abort_msg=yes], [libc_has_abort_msg=no])
+AC_MSG_RESULT($libc_has_abort_msg)
+if test "$libc_has_abort_msg" = "yes"; then
+    AC_DEFINE(HAVE_LIBC_ABORT_MSG,1,[Whether libc defines __abort_msg])
+fi
+
 dnl ******************************************************************
 dnl *** Look for glib-genmarshal in PATH if we are cross-compiling ***
 dnl ******************************************************************

glib/gtestutils.c

@@ -40,6 +40,19 @@
 #ifdef HAVE_SYS_SELECT_H
 #include <sys/select.h>
 #endif /* HAVE_SYS_SELECT_H */
+ 
+/* if we have a recent enough glibc, use its __abort_msg variable for storing
+ * assertion messages (just like assert()). If not, declare our own variable,
+ * so that platforms with older glibc or different libc implementations can use
+ * this feature for debugging as well.
+ */
+#ifdef HAVE_LIBC_ABORT_MSG
+extern char *__abort_msg;
+#define ASSERT_MESSAGE_STORE __abort_msg
+#else
+char *__glib_assert_msg = NULL;
+#define ASSERT_MESSAGE_STORE __glib_assert_msg
+#endif
 
 /* --- structures --- */
 struct GTestCase
@@ -1297,6 +1310,16 @@ g_assertion_message (const char     *domain,
                    func, func[0] ? ":" : "",
                    " ", message, NULL);
   g_printerr ("**\n%s\n", s);
+
+  /* store assertion message in global variable, so that it can be found in a
+   * core dump; also, use standard C allocation here for compatiblity with
+   * glibc's __abort_msg variable */
+  if (ASSERT_MESSAGE_STORE != NULL)
+      /* free the old one */
+      free (ASSERT_MESSAGE_STORE);
+  ASSERT_MESSAGE_STORE = (char*) malloc (strlen (s) + 1);
+  strcpy (ASSERT_MESSAGE_STORE, s);
+
   g_test_log (G_TEST_LOG_ERROR, s, NULL, 0, NULL);
   g_free (s);
   abort();

tests/.gitignore

@@ -1,3 +1,4 @@
+assert-msg-test
 asyncqueue-test
 atomic-test
 base64-test

tests/Makefile.am

@@ -64,7 +64,8 @@ noinst_PROGRAMS = $(TEST_PROGS)	\
 	unicode-normalize 	\
 	unicode-collate 	\
 	$(timeloop) 		\
-	errorcheck-mutex-test
+	errorcheck-mutex-test	\
+	assert-msg-test
 
 TEST_PROGS              += scannerapi
 scannerapi_SOURCES       = scannerapi.c
@@ -82,6 +83,7 @@ testgdate_LDADD = $(libglib)
 testgdateparser_LDADD = $(libglib)
 unicode_normalize_LDADD = $(libglib)
 errorcheck_mutex_test_LDADD = $(libglib) $(libgthread) $(G_THREAD_LIBS) 
+assert_msg_test_LDADD = $(libglib)
 if ENABLE_TIMELOOP
 timeloop_LDADD = $(libglib)
 timeloop_closure_LDADD = $(libglib) $(libgobject)
@@ -136,7 +138,7 @@ test_programs =					\
 	uri-test				\
 	regex-test
 
-test_scripts = run-markup-tests.sh run-collate-tests.sh run-bookmark-test.sh
+test_scripts = run-markup-tests.sh run-collate-tests.sh run-bookmark-test.sh run-assert-msg-test.sh
 
 test_script_support_programs = markup-test unicode-collate bookmarkfile-test
 

tests/assert-msg-test.c

@@ -0,0 +1,8 @@
+#include <glib.h>
+
+int main()
+{
+    g_assert(42 < 0);
+    return 0;
+}
+

tests/run-assert-msg-test.sh

@@ -0,0 +1,48 @@
+#! /bin/sh
+
+fail ()
+{
+  echo "Test failed: $*"
+  exit 1
+}
+
+echo_v ()
+{
+  if [ "$verbose" = "1" ]; then
+    echo "$*"
+  fi
+}
+
+error_out=/dev/null
+if [ "$1" = "-v" ]; then
+  verbose=1
+  error_out=/dev/stderr
+fi  
+
+echo_v "Running assert-msg-test"
+OUT=$(./assert-msg-test 2>&1) && fail "assert-msg-test should abort"
+echo "$OUT" | grep -q '^ERROR:assert-msg-test.c:.*:main: assertion failed: (42 < 0)' || \
+  fail "does not print assertion message"
+
+if ! type gdb >/dev/null 2>&1; then
+  echo_v "Skipped (no gdb installed)"
+  exit 0
+fi
+
+# do we use libc's or our own variable?
+if grep -q '^#define HAVE_LIBC_ABORT_MSG' $(dirname $0)/../config.h; then
+  VAR=__abort_msg
+else
+  VAR=__glib_assert_msg
+fi
+
+echo_v "Running gdb on assert-msg-test"
+OUT=$(gdb --batch --ex run --ex "print (char*) $VAR" .libs/lt-assert-msg-test 2> $error_out) || \
+  fail "failed to run gdb"
+
+echo_v "Checking if assert message is in $VAR"
+if ! echo "$OUT" | grep -q '^$1.*"ERROR:assert-msg-test.c:.*:main: assertion failed: (42 < 0)"'; then
+  fail "$VAR does not have assertion message"
+fi
+
+echo_v "All tests passed."