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[C++] Always use setjmp/longjmp for exceptions 

We currently throw exceptions from signal handlers (e.g., for
Quit/ctrl-c).  But throwing C++ exceptions from signal handlers is
undefined.  (That doesn't restore signal masks, like siglongjmp does,
and, because asynchronous signals can arrive at any instruction, we'd
have to build _everything_ with -fasync-unwind-tables to make it
reliable.)  It happens to work on x86_64 GNU/Linux at least, but it's
likely broken on other ports.

Until we stop throwing from signal handlers, use setjmp/longjmp based
exceptions in C++ mode as well.

gdb/ChangeLog:
2015-11-17  Pedro Alves  <palves@redhat.com>

	* common/common-exceptions.h (GDB_XCPT_SJMP, GDB_XCPT_TRY)
	(GDB_XCPT_RAW_TRY, GDB_XCPT): Define.
	Replace __cplusplus checks with GDB_XCPT checks throughout.
	* common/common-exceptions.c: Replace __cplusplus checks with
	GDB_XCPT checks throughout.
This commit is contained in:
Pedro Alves 2015-11-17 15:17:46 +00:00
parent 91ee7171d0
commit eec461d0a8
3 changed files with 41 additions and 16 deletions
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8
gdb/ChangeLog
View File

@ -1,3 +1,11 @@
2015-11-17 Pedro Alves <palves@redhat.com>
* common/common-exceptions.h (GDB_XCPT_SJMP, GDB_XCPT_TRY)
(GDB_XCPT_RAW_TRY, GDB_XCPT): Define.
Replace __cplusplus checks with GDB_XCPT checks throughout.
* common/common-exceptions.c: Replace __cplusplus checks with
GDB_XCPT checks throughout.
2015-11-17 Pedro Alves <palves@redhat.com>
* common/common-defs.h (ATTRIBUTE_PRINTF): Redefine in terms of

10
gdb/common/common-exceptions.c
View File

@ -22,7 +22,7 @@
const struct gdb_exception exception_none = { (enum return_reason) 0, GDB_NO_ERROR, NULL };
#ifndef __cplusplus
#if GDB_XCPT == GDB_XCPT_SJMP
/* Possible catcher states. */
enum catcher_state {
@ -213,7 +213,7 @@ exceptions_state_mc_action_iter_1 (void)
return exceptions_state_mc (CATCH_ITER_1);
}
#else /* !__cplusplus */
#else /* !GDB_XCPT_SJMP */
/* How many nested TRY blocks we have. See exception_messages and
throw_it. */
@ -261,7 +261,7 @@ gdb_exception_sliced_copy (struct gdb_exception *to, const struct gdb_exception
*to = *from;
}
#endif /* !__cplusplus */
#endif /* !GDB_XCPT_SJMP */
/* Return EXCEPTION to the nearest containing catch_errors(). */
@ -272,7 +272,7 @@ throw_exception (struct gdb_exception exception)
do_cleanups (all_cleanups ());
#ifndef __cplusplus
#if GDB_XCPT == GDB_XCPT_SJMP
/* Jump to the containing catch_errors() call, communicating REASON
to that call via setjmp's return value. Note that REASON can't
be zero, by definition in defs.h. */
@ -320,7 +320,7 @@ throw_it (enum return_reason reason, enum errors error, const char *fmt,
{
struct gdb_exception e;
char *new_message;
#ifndef __cplusplus
#if GDB_XCPT == GDB_XCPT_SJMP
int depth = catcher_list_size ();
#else
int depth = try_scope_depth;

39
gdb/common/common-exceptions.h
View File

@ -116,12 +116,32 @@ struct gdb_exception
const char *message;
};
/* The different exception mechanisms that TRY/CATCH can map to. */
/* Make GDB exceptions use setjmp/longjmp behind the scenes. This is
the only mode supported when GDB is built as a C program. */
#define GDB_XCPT_SJMP 1
/* Make GDB exceptions use try/catch behind the scenes. Can't be made
the default until we stop throwing exceptions from signal
handlers. */
#define GDB_XCPT_TRY 2
/* Specify this mode to build with TRY/CATCH mapped directly to raw
try/catch. GDB won't work correctly, but building that way catches
code tryin to break/continue out of the try block, along with
spurious code between the TRY and the CATCH block. */
#define GDB_XCPT_RAW_TRY 3
/* Always use setjmp/longmp, even in C++ mode. */
#define GDB_XCPT GDB_XCPT_SJMP
/* Functions to drive the exceptions state machine. Though declared
here by necessity, these functions should be considered internal to
the exceptions subsystem and not used other than via the TRY/CATCH
macros defined below. */
#ifndef __cplusplus
#if GDB_XCPT == GDB_XCPT_SJMP
extern SIGJMP_BUF *exceptions_state_mc_init (void);
extern int exceptions_state_mc_action_iter (void);
extern int exceptions_state_mc_action_iter_1 (void);
@ -157,7 +177,7 @@ extern void exception_rethrow (void);
*/
#ifndef __cplusplus
#if GDB_XCPT == GDB_XCPT_SJMP
#define TRY \
{ \
@ -176,7 +196,9 @@ extern void exception_rethrow (void);
#define END_CATCH \
}
#else
#endif /* GDB_XCPT_SJMP */
#if GDB_XCPT == GDB_XCPT_TRY || GDB_XCPT == GDB_XCPT_RAW_TRY
/* Prevent error/quit during TRY from calling cleanups established
prior to here. This pops out the scope in either case of normal
@ -195,13 +217,7 @@ struct exception_try_scope
void *saved_state;
};
/* Define this to build with TRY/CATCH mapped directly to raw
try/catch. GDB won't work correctly, but building that way catches
code tryin to break/continue out of the try block, along with
spurious code between the TRY and the CATCH block. */
//#define USE_RAW_CXX_TRY
#ifndef USE_RAW_CXX_TRY
#if GDB_XCPT == GDB_XCPT_TRY
/* We still need to wrap TRY/CATCH in C++ so that cleanups and C++
exceptions can coexist. The TRY blocked is wrapped in a
@ -224,6 +240,7 @@ struct exception_try_scope
{ \
exception_rethrow (); \
}
#else
#define TRY try
@ -249,7 +266,7 @@ struct gdb_exception_RETURN_MASK_QUIT : public gdb_exception_RETURN_MASK_ALL
{
};
#endif
#endif /* GDB_XCPT_TRY || GDB_XCPT_RAW_TRY */
/* *INDENT-ON* */