Demangler crash handler

This commit wraps calls to the demangler with a segmentation fault
handler.  The first time a segmentation fault is caught a core file
is generated and the user is prompted to file a bug and offered the
choice to exit or to continue their GDB session.  A maintainence
option is provided to allow the user to disable the crash handler
if required.

gdb/
2014-06-19  Gary Benson  <gbenson@redhat.com>

	* configure.ac [AC_CHECK_FUNCS] <sigaltstack>: New check.
	* configure: Regenerate.
	* config.in: Likewise.
	* main.c (signal.h): New include.
	(setup_alternate_signal_stack): New function.
	(captured_main): Call the above.
	* cp-support.c (signal.h): New include.
	(catch_demangler_crashes): New flag.
	(SIGJMP_BUF): New define.
	(SIGSETJMP): Likewise.
	(SIGLONGJMP): Likewise.
	(gdb_demangle_jmp_buf): New static global.
	(gdb_demangle_attempt_core_dump): Likewise.
	(gdb_demangle_signal_handler): New function.
	(gdb_demangle): If catch_demangler_crashes is set, install the
	above signal handler before calling bfd_demangle, and restore
	the original signal handler afterwards.  Display the offending
	symbol and call demangler_warning the first time a segmentation
	fault is caught.
	(_initialize_cp_support): New maint set/show command.

gdb/doc/
2014-06-19  Gary Benson  <gbenson@redhat.com>

	* gdb.texinfo (Maintenance Commands): Document new
	"maint set/show catch-demangler-crashes" option.

1 files changed, 25 insertions, 0 deletions

diff --git a/gdb/main.c b/gdb/main.c
index 108759dcc3..0d4d5122f2 100644
--- a/gdb/main.c
+++ b/gdb/main.c
@@ -45,6 +45,7 @@
 
 #include "filenames.h"
 #include "filestuff.h"
+#include <signal.h>
 
 /* The selected interpreter.  This will be used as a set command
    variable, so it should always be malloc'ed - since
@@ -288,6 +289,27 @@ get_init_files (const char **system_gdbinit,
   *local_gdbinit = localinit;
 }
 
+/* Try to set up an alternate signal stack for SIGSEGV handlers.
+   This allows us to handle SIGSEGV signals generated when the
+   normal process stack is exhausted.  If this stack is not set
+   up (sigaltstack is unavailable or fails) and a SIGSEGV is
+   generated when the normal stack is exhausted then the program
+   will behave as though no SIGSEGV handler was installed.  */
+
+static void
+setup_alternate_signal_stack (void)
+{
+#ifdef HAVE_SIGALTSTACK
+  stack_t ss;
+
+  ss.ss_sp = xmalloc (SIGSTKSZ);
+  ss.ss_size = SIGSTKSZ;
+  ss.ss_flags = 0;
+
+  sigaltstack(&ss, NULL);
+#endif
+}
+
 /* Call command_loop.  If it happens to return, pass that through as a
    non-zero return status.  */
 
@@ -785,6 +807,9 @@ captured_main (void *data)
       quiet = 1;
   }
 
+  /* Try to set up an alternate signal stack for SIGSEGV handlers.  */
+  setup_alternate_signal_stack ();
+
   /* Initialize all files.  Give the interpreter a chance to take
      control of the console via the deprecated_init_ui_hook ().  */
   gdb_init (gdb_program_name);