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[Bug gdb/20977] GDB exception handling is broken on i686-w64-mingw32


https://sourceware.org/bugzilla/show_bug.cgi?id=20977

--- Comment #2 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The gdb-7.12-branch branch has been updated by Pedro Alves
<palves@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=ada8ff522ce970e11dae4a3463c899b64e6f5006

commit ada8ff522ce970e11dae4a3463c899b64e6f5006
Author: Pedro Alves <palves@redhat.com>
Date:   Tue Dec 20 16:25:54 2016 +0000

    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.

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