[Bug tdep/30102] [gdb/tdep, amd64] Disable i386 unwinders

["cvs-commit at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=30102

--- Comment #4 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Tom de Vries <vries@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=af0d0f34d8bf7482e598308b54e7ba0ae9b0c349

commit af0d0f34d8bf7482e598308b54e7ba0ae9b0c349
Author: Tom de Vries <tdevries@suse.de>
Date:   Sat Feb 11 09:04:51 2023 +0100

    [gdb/tdep] Don't use i386 unwinder for amd64

    For i386 we have these unwinders:
    ...
    $ gdb -q -batch -ex "set arch i386" -ex "maint info frame-unwinders"
    The target architecture is set to "i386".
    dummy                   DUMMY_FRAME
    dwarf2 tailcall         TAILCALL_FRAME
    inline                  INLINE_FRAME
    i386 epilogue           NORMAL_FRAME
    dwarf2                  NORMAL_FRAME
    dwarf2 signal           SIGTRAMP_FRAME
    i386 stack tramp        NORMAL_FRAME
    i386 sigtramp           SIGTRAMP_FRAME
    i386 prologue           NORMAL_FRAME
    ...
    and for amd64:
    ...
    $ gdb -q -batch -ex "set arch i386:x86-64" -ex "maint info frame-unwinders"
    The target architecture is set to "i386:x86-64".
    dummy                   DUMMY_FRAME
    dwarf2 tailcall         TAILCALL_FRAME
    inline                  INLINE_FRAME
    python                  NORMAL_FRAME
    amd64 epilogue          NORMAL_FRAME
    i386 epilogue           NORMAL_FRAME
    dwarf2                  NORMAL_FRAME
    dwarf2 signal           SIGTRAMP_FRAME
    amd64 sigtramp          SIGTRAMP_FRAME
    amd64 prologue          NORMAL_FRAME
    i386 stack tramp        NORMAL_FRAME
    i386 sigtramp           SIGTRAMP_FRAME
    i386 prologue           NORMAL_FRAME
    ...

    ISTM me there's no reason for the i386 unwinders to be there for amd64.

    Furthermore, there's a generic need to play around with enabling and
disabling
    unwinders, see PR8434.  Currently, that's only available for both the
dwarf2
    unwinders at once using "maint set dwarf unwinders on/off".

    If I manually disable the "amd64 epilogue" unwinder, the "i386 epilogue"
    unwinder becomes active and gives the wrong answer, while I'm actually
    interested in the result of the dwarf2 unwinder.  Of course I can also
    manually disable the "i386 epilogue", but I take the fact that I have to do
    that as evidence that on amd64, the "i386 epilogue" is not only
unnecessary,
    but in the way.

    Fix this by only adding the i386 unwinders if
    "info.bfd_arch_info->bits_per_word == 32".

    Note that the x32 abi (x86_64/-mx32):
    - has the same unwinder list as amd64 (x86_64/-m64) before this commit,
    - has info.bfd_arch_info->bits_per_word == 64, the same as amd64, and
      consequently,
    - has the same unwinder list as amd64 after this commit.

    Tested on x86_64-linux, -m64 and -m32.  Not tested with -mx32.

    Reviewed-By: John Baldwin <jhb@freebsd.org>

    PR tdep/30102
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30102

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