[PATCH 2/2] Demangler crash handler

[Gary Benson <gbenson@redhat.com>]

This patch wraps calls to the demangler with a segmentation fault
handler.  A warning is printed the first time a segmentation fault
is caught.

gdb/
2014-05-09  Gary Benson  <gbenson@redhat.com>

	PR backtrace/16817
	* cp-support.c (signal.h): New include.
	(gdb_demangle_signal_handler): New function.
	(gdb_demangle): Install the above signal handler before calling
	bfd_demangle, and restore the original signal handler afterwards.

gdb/testsuite/
2014-05-09  Gary Benson  <gbenson@redhat.com>

	PR backtrace/16817
	* gdb.base/pr16817.exp: New file.

diff --git a/gdb/cp-support.c b/gdb/cp-support.c
index 91533e8..f1a0d49 100644
--- a/gdb/cp-support.c
+++ b/gdb/cp-support.c
@@ -36,6 +36,7 @@
 #include "value.h"
 #include "cp-abi.h"
 #include "language.h"
+#include <signal.h>
 
 #include "safe-ctype.h"
 
@@ -1505,12 +1506,71 @@ cp_lookup_rtti_type (const char *name, struct block *block)
   return rtti_type;
 }
 
+/* Signal handler for gdb_demangle.  */
+
+static void
+gdb_demangle_signal_handler (int signo)
+{
+  throw_error (GENERIC_ERROR, _("demangler failed with signal %d"),
+	       signo);
+}
+
 /* A wrapper for bfd_demangle.  */
 
 char *
 gdb_demangle (const char *name, int options)
 {
-  return bfd_demangle (NULL, name, options);
+  char *result = NULL;
+
+#ifdef SIGSEGV
+  volatile struct gdb_exception except;
+
+#if defined (HAVE_SIGACTION) && defined (SA_RESTART)
+  struct sigaction sa, old_sa;
+
+  sa.sa_handler = gdb_demangle_signal_handler;
+  sigemptyset (&sa.sa_mask);
+  sa.sa_flags = 0;
+  sigaction (SIGSEGV, &sa, &old_sa);
+#else
+  void (*ofunc) ();
+
+  ofunc = (void (*)()) signal (SIGSEGV, gdb_demangle_signal_handler);
+#endif
+#endif
+
+  TRY_CATCH (except, RETURN_MASK_ALL)
+    {
+      result = bfd_demangle (NULL, name, options);
+    }
+
+#ifdef SIGSEGV
+#if defined (HAVE_SIGACTION) && defined (SA_RESTART)
+  sigaction (SIGSEGV, &old_sa, NULL);
+#else
+  signal (SIGSEGV, ofunc);
+#endif
+#endif
+
+  if (except.reason < 0)
+    {
+      static int warning_printed = 0;
+
+      if (!warning_printed)
+	{
+	  warning ("internal error: %s\n"
+		   "Unable to demangle '%s'\n"
+		   "This is a bug, "
+		   "please report it to the GDB maintainers.",
+		   except.message, name);
+
+	  warning_printed = 1;
+	}
+
+      result = NULL;
+    }
+
+  return result;
 }
 
 /* Don't allow just "maintenance cplus".  */
diff --git a/gdb/testsuite/gdb.base/pr16817.exp b/gdb/testsuite/gdb.base/pr16817.exp
new file mode 100644
index 0000000..fff022c
--- /dev/null
+++ b/gdb/testsuite/gdb.base/pr16817.exp
@@ -0,0 +1,25 @@
+# Copyright 2014 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/>.
+
+# Test that a segmentation fault in the demangler does not cause GDB
+# to crash.  If the demangler becomes able to demangle the below
+# symbol then another symbol will need to be found for this test.
+
+set symbol "_QueueNotification_QueueController__\$4PPPPPPPM_A_INotice___Z"
+
+gdb_exit
+gdb_start
+gdb_test_no_output "set lang c++"
+gdb_test "maint demangle $symbol" ".*demangler failed.*"