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

1 files changed, 23 insertions, 0 deletions

diff --git a/glib/gtestutils.c b/glib/gtestutils.c
index fdb9494..36a0a8e 100644
--- a/glib/gtestutils.c
+++ b/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();