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

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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".
This commit is contained in:
Pedro Alves 2016-04-12 17:20:04 +01:00
parent 2afc13ff80
commit 173981bc49
4 changed files with 21 additions and 8 deletions
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13
gdb/ChangeLog
View file

@ -1,3 +1,16 @@
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".
2016-04-12 Pedro Alves <palves@redhat.com>
* common/common-exceptions.c (exception_rethrow): Remove

6
gdb/common/common-exceptions.c
View file

@ -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)
{

8
gdb/common/common-exceptions.h
View file

@ -20,7 +20,7 @@
#ifndef COMMON_EXCEPTIONS_H
#define COMMON_EXCEPTIONS_H
#include "gdb_setjmp.h"
#include <setjmp.h>
/* Reasons for calling throw_exceptions(). NOTE: all reason values
must be less than zero. enum value 0 is reserved for internal use
@ -142,7 +142,7 @@ struct gdb_exception
macros defined below. */
#if GDB_XCPT == GDB_XCPT_SJMP
extern SIGJMP_BUF *exceptions_state_mc_init (void);
extern jmp_buf *exceptions_state_mc_init (void);
extern int exceptions_state_mc_action_iter (void);
extern int exceptions_state_mc_action_iter_1 (void);
extern int exceptions_state_mc_catch (struct gdb_exception *, int);
@ -181,9 +181,9 @@ extern void exception_rethrow (void);
#define TRY \
{ \
SIGJMP_BUF *buf = \
jmp_buf *buf = \
exceptions_state_mc_init (); \
SIGSETJMP (*buf); \
setjmp (*buf); \
} \
while (exceptions_state_mc_action_iter ()) \
while (exceptions_state_mc_action_iter_1 ())

2
gdb/cp-support.c
View file

@ -34,7 +34,7 @@
#include "cp-abi.h"
#include "namespace.h"
#include <signal.h>
#include "gdb_setjmp.h"
#include "safe-ctype.h"
#define d_left(dc) (dc)->u.s_binary.left