[Bug symtab/30911] [gdb/symtab] Cannot call ifunc strstr with debuginfo installed

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

https://sourceware.org/bugzilla/show_bug.cgi?id=30911

--- Comment #5 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=1d45d90934b10862c00a22bcf4075815a785001b

commit 1d45d90934b10862c00a22bcf4075815a785001b
Author: Tom de Vries <tdevries@suse.de>
Date:   Mon Oct 16 16:32:28 2023 +0200

    [gdb/symtab] Work around PR gas/29517

    When using glibc debuginfo generated with gas 2.39, we run into PR
gas/29517:
    ...
    $ gdb -q -batch a.out -ex start -ex "p (char *)strstr (\"haha\", \"ah\")"
    Temporary breakpoint 1 at 0x40051b: file hello.c, line 6.

    Temporary breakpoint 1, main () at hello.c:6
    6         printf ("hello\n");
    Invalid cast.
    ...
    while without glibc debuginfo installed we get the expected result:
    ...
    $n = 0x7ffff7daa1b1 "aha"
    ...
    and likewise with glibc debuginfo generated with gas 2.40.

    The strstr ifunc resolves to __strstr_sse2_unaligned.  The problem is that
gas
    generates dwarf that states that the return type is void:
    ...
    <1><3e1e58>: Abbrev Number: 2 (DW_TAG_subprogram)
        <3e1e59>   DW_AT_name        : __strstr_sse2_unaligned
        <3e1e5d>   DW_AT_external    : 1
        <3e1e5e>   DW_AT_low_pc      : 0xbbd2e
        <3e1e66>   DW_AT_high_pc     : 0xbc1c3
    ...
    while the return type should be a DW_TAG_unspecified_type, as is the case
    with gas 2.40.

    We can still use the workaround of casting to another function type for
both
    __strstr_sse2_unaligned:
    ...
    (gdb) p ((char * (*) (const char *, const char *))__strstr_sse2_unaligned)
\
      ("haha", "ah")
    $n = 0x7ffff7daa211 "aha"
    ...
    and strstr (which requires using *strstr to dereference the ifunc before we
    cast):
    ...
    gdb) p ((char * (*) (const char *, const char *))*strstr) ("haha", "ah")
    $n = 0x7ffff7daa251 "aha"
    ...
    but that's a bit cumbersome to use.

    Work around this in the dwarf reader, such that we have instead:
    ...
    (gdb) p (char *)strstr ("haha", "ah")
    $n = 0x7ffff7daa1b1 "aha"
    ...

    This also requires fixing producer_is_gcc to stop returning true for
    producer "GNU AS 2.39.0".

    Tested on x86_64-linux.

    Approved-By: Andrew Burgess <aburgess@redhat.com>

    PR symtab/30911
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30911

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