git-floatn-gcc-13-support

git-floatn-gcc-13-support

commit 3e5760fcb48528d48deeb60cb885a97bb731160c
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Wed Sep 28 20:09:34 2022 +0000

    Update _FloatN header support for C++ in GCC 13

    GCC 13 adds support for _FloatN and _FloatNx types in C++, so breaking
    the installed glibc headers that assume such support is not present.
    GCC mostly works around this with fixincludes, but that doesn't help
    for building glibc and its tests (glibc doesn't itself contain C++
    code, but there's C++ code built for tests).  Update glibc's
    bits/floatn-common.h and bits/floatn.h headers to handle the GCC 13
    support directly.

    In general the changes match those made by fixincludes, though I think
    the ones in sysdeps/powerpc/bits/floatn.h, where the header tests
    __LDBL_MANT_DIG__ == 113 or uses #elif, wouldn't match the existing
    fixincludes patterns.

    Some places involving special C++ handling in relation to _FloatN
    support are not changed.  There's no need to change the
    __HAVE_FLOATN_NOT_TYPEDEF definition (also in a form that wouldn't be
    matched by the fixincludes fixes) because it's only used in relation
    to macro definitions using features not supported for C++
    (__builtin_types_compatible_p and _Generic).  And there's no need to
    change the inline function overloads for issignaling, iszero and
    iscanonical in C++ because cases where types have the same format but
    are no longer compatible types are handled automatically by the C++
    overload resolution rules.

    This patch also does not change the overload handling for iseqsig, and
    there I think changes *are* needed, beyond those in this patch or made
    by fixincludes.  The way that overload is defined, via a template
    parameter to a structure type, requires overloads whenever the types
    are incompatible, even if they have the same format.  So I think we
    need to add overloads with GCC 13 for every supported _FloatN and
    _FloatNx type, rather than just having one for _Float128 when it has a
    different ABI to long double as at present (but for older GCC, such
    overloads must not be defined for types that end up defined as
    typedefs for another type).

    Tested with build-many-glibcs.py: compilers build for
    aarch64-linux-gnu ia64-linux-gnu mips64-linux-gnu powerpc-linux-gnu
    powerpc64le-linux-gnu x86_64-linux-gnu; glibcs build for
    aarch64-linux-gnu ia64-linux-gnu i686-linux-gnu mips-linux-gnu
    mips64-linux-gnu-n32 powerpc-linux-gnu powerpc64le-linux-gnu
    x86_64-linux-gnu.

Gbp-Pq: Topic any
Gbp-Pq: Name git-floatn-gcc-13-support.diff