[Bug debug/111735] incorrect BTF representation of forward-declared enums

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111735

--- Comment #2 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by David Faust <dfaust@gcc.gnu.org>:

https://gcc.gnu.org/g:1502d724df85163b14b04e8f67072ca88eac411d

commit r14-6716-g1502d724df85163b14b04e8f67072ca88eac411d
Author: David Faust <david.faust@oracle.com>
Date:   Tue Dec 12 13:55:59 2023 -0800

    btf: change encoding of forward-declared enums [PR111735]

    The BTF specification does not formally define a representation for
    forward-declared enum types such as:

      enum Foo;

    Forward-declarations for struct and union types are represented by
    BTF_KIND_FWD, which has a 1-bit flag distinguishing the two.

    The de-facto standard format used by other tools like clang and pahole
    is to represent forward-declared enums as BTF_KIND_ENUM with vlen=0,
    i.e. as a regular enum type with no enumerators.  This patch changes
    GCC to adopt that format, and makes a couple of minor cleanups in
    btf_asm_type ().

    gcc/

            PR debug/111735
            * btfout.cc (btf_fwd_to_enum_p): New.
            (btf_asm_type_ref): Special case references to enum forwards.
            (btf_asm_type): Special case enum forwards. Rename btf_size_type to
            btf_size, and change chained ifs switching on btf_kind into else
ifs.

    gcc/testsuite/

            PR debug/111735
            * gcc.dg/debug/btf/btf-forward-2.c: New test.