[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.
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2015-11-17 Pedro Alves <palves@redhat.com>
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* common/common-exceptions.h (GDB_XCPT_SJMP, GDB_XCPT_TRY)
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(GDB_XCPT_RAW_TRY, GDB_XCPT): Define.
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Replace __cplusplus checks with GDB_XCPT checks throughout.
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* common/common-exceptions.c: Replace __cplusplus checks with
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GDB_XCPT checks throughout.
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2015-11-17 Pedro Alves <palves@redhat.com>
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* common/common-defs.h (ATTRIBUTE_PRINTF): Redefine in terms of
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@ -22,7 +22,7 @@
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const struct gdb_exception exception_none = { (enum return_reason) 0, GDB_NO_ERROR, NULL };
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#ifndef __cplusplus
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#if GDB_XCPT == GDB_XCPT_SJMP
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/* Possible catcher states. */
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enum catcher_state {
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@ -213,7 +213,7 @@ exceptions_state_mc_action_iter_1 (void)
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return exceptions_state_mc (CATCH_ITER_1);
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}
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#else /* !__cplusplus */
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#else /* !GDB_XCPT_SJMP */
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/* How many nested TRY blocks we have. See exception_messages and
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throw_it. */
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@ -261,7 +261,7 @@ gdb_exception_sliced_copy (struct gdb_exception *to, const struct gdb_exception
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*to = *from;
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}
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#endif /* !__cplusplus */
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#endif /* !GDB_XCPT_SJMP */
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/* Return EXCEPTION to the nearest containing catch_errors(). */
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@ -272,7 +272,7 @@ throw_exception (struct gdb_exception exception)
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do_cleanups (all_cleanups ());
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#ifndef __cplusplus
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#if GDB_XCPT == GDB_XCPT_SJMP
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/* Jump to the containing catch_errors() call, communicating REASON
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to that call via setjmp's return value. Note that REASON can't
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be zero, by definition in defs.h. */
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@ -320,7 +320,7 @@ throw_it (enum return_reason reason, enum errors error, const char *fmt,
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{
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struct gdb_exception e;
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char *new_message;
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#ifndef __cplusplus
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#if GDB_XCPT == GDB_XCPT_SJMP
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int depth = catcher_list_size ();
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#else
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int depth = try_scope_depth;
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@ -116,12 +116,32 @@ struct gdb_exception
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const char *message;
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};
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/* The different exception mechanisms that TRY/CATCH can map to. */
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/* Make GDB exceptions use setjmp/longjmp behind the scenes. This is
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the only mode supported when GDB is built as a C program. */
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#define GDB_XCPT_SJMP 1
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/* Make GDB exceptions use try/catch behind the scenes. Can't be made
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the default until we stop throwing exceptions from signal
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handlers. */
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#define GDB_XCPT_TRY 2
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/* Specify this mode to build with TRY/CATCH mapped directly to raw
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try/catch. GDB won't work correctly, but building that way catches
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code tryin to break/continue out of the try block, along with
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spurious code between the TRY and the CATCH block. */
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#define GDB_XCPT_RAW_TRY 3
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/* Always use setjmp/longmp, even in C++ mode. */
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#define GDB_XCPT GDB_XCPT_SJMP
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/* Functions to drive the exceptions state machine. Though declared
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here by necessity, these functions should be considered internal to
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the exceptions subsystem and not used other than via the TRY/CATCH
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macros defined below. */
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#ifndef __cplusplus
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#if GDB_XCPT == GDB_XCPT_SJMP
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extern SIGJMP_BUF *exceptions_state_mc_init (void);
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extern int exceptions_state_mc_action_iter (void);
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extern int exceptions_state_mc_action_iter_1 (void);
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@ -157,7 +177,7 @@ extern void exception_rethrow (void);
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*/
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#ifndef __cplusplus
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#if GDB_XCPT == GDB_XCPT_SJMP
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#define TRY \
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{ \
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#define END_CATCH \
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}
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#else
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#endif /* GDB_XCPT_SJMP */
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#if GDB_XCPT == GDB_XCPT_TRY || GDB_XCPT == GDB_XCPT_RAW_TRY
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/* Prevent error/quit during TRY from calling cleanups established
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prior to here. This pops out the scope in either case of normal
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@ -195,13 +217,7 @@ struct exception_try_scope
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void *saved_state;
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};
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/* Define this to build with TRY/CATCH mapped directly to raw
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try/catch. GDB won't work correctly, but building that way catches
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code tryin to break/continue out of the try block, along with
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spurious code between the TRY and the CATCH block. */
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//#define USE_RAW_CXX_TRY
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#ifndef USE_RAW_CXX_TRY
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#if GDB_XCPT == GDB_XCPT_TRY
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/* We still need to wrap TRY/CATCH in C++ so that cleanups and C++
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exceptions can coexist. The TRY blocked is wrapped in a
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{ \
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exception_rethrow (); \
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}
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#else
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#define TRY try
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@ -249,7 +266,7 @@ struct gdb_exception_RETURN_MASK_QUIT : public gdb_exception_RETURN_MASK_ALL
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{
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};
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#endif
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#endif /* GDB_XCPT_TRY || GDB_XCPT_RAW_TRY */
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/* *INDENT-ON* */
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