Use setjmp/longjmp for TRY/CATCH instead of sigsetjmp/siglongjmp

Now that we don't ever throw GDB exceptions from signal handlers [1],
we can switch to have TRY/CATCH implemented in terms of plain
setjmp/longjmp instead of sigsetjmp/siglongjmp.

In https://sourceware.org/ml/gdb-patches/2015-02/msg00114.html, Yichun
Zhang mentions a 11%/14%+ speedup in his GDB python scripts with a
patch that did something similar to only a specific set of TRY/CATCH
calls.

[1] - https://sourceware.org/ml/gdb-patches/2016-03/msg00351.html

Tested on x86_64 Fedora 23, native and gdbserver.

gdb/ChangeLog:
2016-04-12  Pedro Alves  <palves@redhat.com>

	* common/common-exceptions.c (struct catcher) <buf>: Now a
	'jmp_buf' instead of SIGJMP_BUF.
	(exceptions_state_mc_init): Change return type to 'jmp_buf'.
	(throw_exception): Use longjmp instead of SIGLONGJMP.
	* common/common-exceptions.h: Include <setjmp.h> instead of
	"gdb_setjmp.h".
	(exceptions_state_mc_init): Change return type to 'jmp_buf'.
	[GDB_XCPT == GDB_XCPT_SJMP] (TRY): Use setjmp instead of
	SIGSETJMP.
	* cp-support.c: Include "gdb_setjmp.h".

1 files changed, 3 insertions, 3 deletions

diff --git a/gdb/common/common-exceptions.c b/gdb/common/common-exceptions.c
index 5ea81880169..2e638620b85 100644
--- a/gdb/common/common-exceptions.c
+++ b/gdb/common/common-exceptions.c
@@ -46,7 +46,7 @@ struct catcher
 {
   enum catcher_state state;
   /* Jump buffer pointing back at the exception handler.  */
-  SIGJMP_BUF buf;
+  jmp_buf buf;
   /* Status buffer belonging to the exception handler.  */
   struct gdb_exception exception;
   struct cleanup *saved_cleanup_chain;
@@ -73,7 +73,7 @@ catcher_list_size (void)
   return size;
 }
 
-SIGJMP_BUF *
+jmp_buf *
 exceptions_state_mc_init (void)
 {
   struct catcher *new_catcher = XCNEW (struct catcher);
@@ -275,7 +275,7 @@ throw_exception (struct gdb_exception exception)
      be zero, by definition in defs.h.  */
   exceptions_state_mc (CATCH_THROWING);
   current_catcher->exception = exception;
-  SIGLONGJMP (current_catcher->buf, exception.reason);
+  longjmp (current_catcher->buf, exception.reason);
 #else
   if (exception.reason == RETURN_QUIT)
     {