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From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug libstdc++/109883] Stack Overflow in <cmath> functions with
 <stdfloat> types and -std=c++23
Date: Wed, 17 May 2023 19:27:28 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109883

--- Comment #11 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-13 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:c42950e2d380d0da26203fb1eb39497c0a400b2d

commit r13-7341-gc42950e2d380d0da26203fb1eb39497c0a400b2d
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Wed May 17 21:21:23 2023 +0200

    libstdc++: Fix up some <cmath> templates [PR109883]

    As can be seen on the following testcase, for
=20=20=20
std::{atan2,fmod,pow,copysign,fdim,fmax,fmin,hypot,nextafter,remainder,remq=
uo,fma}
    if one operand type is std::float{16,32,64,128}_t or std::bfloat16_t and
    another one some integral type or some other floating point type which
    promotes to the other operand's type, we can end up with endless recurs=
ion.
    This is because of a declaration ordering problem in <cmath>, where the
    float, double and long double overloads of those functions come before
    the templates which use __gnu_cxx::__promote_{2,3}, but the
    std::float{16,32,64,128}_t and std::bfloat16_t overloads come later in =
the
    file.  If the result of those promotions is _Float{16,32,64,128} or
    __gnu_cxx::__bfloat16_t, say std::pow(_Float64, int) calls
    std::pow(_Float64, _Float64) and the latter calls itself.

    The following patch fixes that by moving those templates later in the f=
ile,
    so that the calls from those templates see also the other overloads.

    I think other templates in the file like e.g. isgreater etc. shouldn't =
be
    a problem, because those just use __builtin_isgreater etc. in their bod=
ies.

    2023-05-17  Jakub Jelinek  <jakub@redhat.com>

            PR libstdc++/109883
            * include/c_global/cmath (atan2, fmod, pow): Move
            __gnu_cxx::__promote_2 using templates after _Float{16,32,64,12=
8}
and
            __gnu_cxx::__bfloat16_t overloads.
            (copysign, fdim, fmax, fmin, hypot, nextafter, remainder, remqu=
o):
            Likewise.
            (fma): Move __gnu_cxx::__promote_3 using template after
            _Float{16,32,64,128} and __gnu_cxx::__bfloat16_t overloads.

            * testsuite/26_numerics/headers/cmath/constexpr_std_c++23.cc: N=
ew
test.

    (cherry picked from commit 883f1e25dc7907c9bb37f480b900336a050218f1)=