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authorPedro Alves <palves@redhat.com>2016-12-20 15:46:44 +0000
committerPedro Alves <palves@redhat.com>2016-12-20 15:46:44 +0000
commit2693a26216c329bd7ec2aae7743409f572de4fa5 (patch)
treee9456ea347835745090a897e127677e61619ce43
parentff71884063d048e8f8c03de27d2bac343df4f77a (diff)
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Fix longjmp across readline w/ --enable-sjlj-exceptions toolchains
Nowadays, GDB propagates C++ exceptions across readline using setjmp/longjmp 89525768cd08 ("Propagate GDB/C++ exceptions across readline using sj/lj-based TRY/CATCH") because DWARF-based unwinding can't cross C functions compiled without -fexceptions (see details from the commit above). Unfortunately, toolchains that use SjLj-based C++ exceptions got broken with that fix, because _Unwind_SjLj_Unregister, which is put at the exit of a function, is not executed due to the longjmp added by that commit. (gdb) [New Thread 2936.0xb80] kill Thread 1 received signal SIGSEGV, Segmentation fault. 0x03ff662b in ?? () top?bt 15 #0 0x03ff662b in ?? () #1 0x00526b92 in stdin_event_handler (error=0, client_data=0x172ed8) at ../../binutils-gdb/gdb/event-top.c:555 #2 0x00525a94 in handle_file_event (ready_mask=<optimized out>, file_ptr=0x3ff5cb8) at ../../binutils-gdb/gdb/event-loop.c:733 #3 gdb_wait_for_event (block=block@entry=1) at ../../binutils-gdb/gdb/event-loop.c:884 #4 0x00525bfb in gdb_do_one_event () at ../../binutils-gdb/gdb/event-loop.c:347 #5 0x00525ce5 in start_event_loop () at ../../binutils-gdb/gdb/event-loop.c:371 #6 0x0051fada in captured_command_loop (data=0x0) at ../../binutils-gdb/gdb/main.c:324 #7 0x0051cf5d in catch_errors ( func=func@entry=0x51fab0 <captured_command_loop(void*)>, func_args=func_args@entry=0x0, errstring=errstring@entry=0x7922bf <VEC_interp_factory_p_quick_push(VEC_inte rp_factory_p*, interp_factory*, char const*, unsigned int)::__PRETTY_FUNCTION__+351> "", mask=mask@entry=RETURN_MASK_ALL) at ../../binutils-gdb/gdb/exceptions.c:236 #8 0x00520f0c in captured_main (data=0x328feb4) at ../../binutils-gdb/gdb/main.c:1149 #9 gdb_main (args=args@entry=0x328feb4) at ../../binutils-gdb/gdb/main.c:1159 #10 0x0071e400 in main (argc=1, argv=0x171220) at ../../binutils-gdb/gdb/gdb.c:32 Fix this by making the functions involved in setjmp/longjmp as noexcept, so that the compiler knows it doesn't need to emit the _Unwind_SjLj_Register / _Unwind_SjLj_Unregister calls for C++ exceptions. Tested on x86_64 Fedora 23 with: - GCC 5.3.1 w/ DWARF-based exceptions. - GCC 7 built with --enable-sjlj-exceptions. gdb/ChangeLog: 2016-12-20 Pedro Alves <palves@redhat.com> Yao Qi <yao.qi@linaro.org> PR gdb/20977 * event-top.c (gdb_rl_callback_read_char_wrapper_noexcept): New noexcept function, factored out from ... (gdb_rl_callback_read_char_wrapper): ... this. (gdb_rl_callback_handler): Mark noexcept.
-rw-r--r--gdb/ChangeLog9
-rw-r--r--gdb/event-top.c23
2 files changed, 27 insertions, 5 deletions
diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 233a43c..5f0e6fe 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,12 @@
+2016-12-20 Pedro Alves <palves@redhat.com>
+ Yao Qi <yao.qi@linaro.org>
+
+ PR gdb/20977
+ * event-top.c (gdb_rl_callback_read_char_wrapper_noexcept): New
+ noexcept function, factored out from ...
+ (gdb_rl_callback_read_char_wrapper): ... this.
+ (gdb_rl_callback_handler): Mark noexcept.
+
2016-12-20 Antoine Tremblay <antoine.tremblay@ericsson.com>
* .dir-locals.el: Set c++ mode for the directory and set indent
diff --git a/gdb/event-top.c b/gdb/event-top.c
index acf8474..fa58def 100644
--- a/gdb/event-top.c
+++ b/gdb/event-top.c
@@ -157,10 +157,12 @@ void (*after_char_processing_hook) (void);
sjlj-based TRY/CATCH mechanism, which knows to handle multiple
levels of active setjmp/longjmp frames, needed in order to handle
the readline callback recursing, as happens with e.g., secondary
- prompts / queries, through gdb_readline_wrapper. */
+ prompts / queries, through gdb_readline_wrapper. This must be
+ noexcept in order to avoid problems with mixing sjlj and
+ (sjlj-based) C++ exceptions. */
-static void
-gdb_rl_callback_read_char_wrapper (gdb_client_data client_data)
+static struct gdb_exception
+gdb_rl_callback_read_char_wrapper_noexcept () noexcept
{
struct gdb_exception gdb_expt = exception_none;
@@ -180,6 +182,15 @@ gdb_rl_callback_read_char_wrapper (gdb_client_data client_data)
}
END_CATCH_SJLJ
+ return gdb_expt;
+}
+
+static void
+gdb_rl_callback_read_char_wrapper (gdb_client_data client_data)
+{
+ struct gdb_exception gdb_expt
+ = gdb_rl_callback_read_char_wrapper_noexcept ();
+
/* Rethrow using the normal EH mechanism. */
if (gdb_expt.reason < 0)
throw_exception (gdb_expt);
@@ -187,10 +198,12 @@ gdb_rl_callback_read_char_wrapper (gdb_client_data client_data)
/* GDB's readline callback handler. Calls the current INPUT_HANDLER,
and propagates GDB exceptions/errors thrown from INPUT_HANDLER back
- across readline. See gdb_rl_callback_read_char_wrapper. */
+ across readline. See gdb_rl_callback_read_char_wrapper. This must
+ be noexcept in order to avoid problems with mixing sjlj and
+ (sjlj-based) C++ exceptions. */
static void
-gdb_rl_callback_handler (char *rl)
+gdb_rl_callback_handler (char *rl) noexcept
{
struct gdb_exception gdb_rl_expt = exception_none;
struct ui *ui = current_ui;