https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61761

--- Comment #10 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Author: redi
Date: Thu Oct 24 12:55:21 2019
New Revision: 277392

URL: https://gcc.gnu.org/viewcvs?rev=277392&root=gcc&view=rev
Log:
PR libstdc++/61761 fix std::proj for targets without C99 cproj

The current generic implementation of __complex_proj used when cproj is
not available calculates the wrong projection, giving a different result
than given by C99's cproj.

When C99 cproj is not available but isinf and copysign are, use those to
give correct results for float, double and long double. Otherwise, and
for other specializations of std::complex, just use a generic version
that returns its argument, and so doesn't support infinities.

We might want to consider adding additional overloads of __complex_proj
to support extended types such as _Float64x, _Float128 etc.

Backport from mainline
2019-05-01  Jonathan Wakely  <jwak...@redhat.com>

        PR libstdc++/61761
        * include/std/complex (__complex_proj): Return parameter unchanged.
        [_GLIBCXX_USE_C99_COMPLEX] (__complex_proj): Change overloads for
        floating-point types to take std::complex arguments.
        [_GLIBCXX_USE_C99_MATH_TR1] (__complex_proj): Add overloads for
        floating-point types.
        * testsuite/26_numerics/complex/proj.cc: New test.

Added:
    branches/gcc-9-branch/libstdc++-v3/testsuite/26_numerics/complex/proj.cc
Modified:
    branches/gcc-9-branch/libstdc++-v3/ChangeLog
    branches/gcc-9-branch/libstdc++-v3/include/std/complex

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