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".

4 files changed, 21 insertions, 8 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 5dfd4b0..b750266 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,18 @@
 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
 	prepare_to_throw_exception call.
 	* common/common-exceptions.h (prepare_to_throw_exception): Delete
diff --git a/gdb/common/common-exceptions.c b/gdb/common/common-exceptions.c
index 5ea8188..2e63862 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)
     {
diff --git a/gdb/common/common-exceptions.h b/gdb/common/common-exceptions.h
index 54c6249..e21713c 100644
--- a/gdb/common/common-exceptions.h
+++ b/gdb/common/common-exceptions.h
@@ -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 ())
diff --git a/gdb/cp-support.c b/gdb/cp-support.c
index c7f5074..5662f86 100644
--- a/gdb/cp-support.c
+++ b/gdb/cp-support.c
@@ -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