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From: Dai Conrad <dai DOT conrad AT gmail DOT com>
Date: Wed, 30 May 2018 12:54:58 -0400
Message-ID: <CAEotdwmH+KbJqDSQstgAgaFra_gmrxxADY_EaV5GCoT_QeKX5A@mail.gmail.com>
Subject: Re: Updated: gcc-7.3.0-2 (x86/x86_64)
To: cygwin mailing list <cygwin AT cygwin DOT com>
Content-Type: text/plain; charset="UTF-8"

On Wed, 30 May 2018 11:58 AM, JonY <10walls AT gmail DOT com> wrote:
>
> Does -static change anything?

Interesting! It succeeds with g++ -std=c++17, and does this with
clang++ -std=c++17:

$ clang++ -std=c++17 -static -Wall -Wextra -O2 -o testa testa.cc
/usr/lib/gcc/x86_64-pc-cygwin/7.3.0/libstdc++.a(cow-string-inst.o):cow-string-inst.cc:(.data$_ZNSs4_Rep20_S_empty_rep_storageE[_ZNSs4_Rep20_S_empty_rep_storageE]+0x0):
multiple definition of `std::string::_Rep::_S_empty_rep_storage'
/tmp/testa-c0acb8.o:(.bss[_ZNSs4_Rep20_S_empty_rep_storageE]+0x0):
first defined here
clang-5.0: error: linker command failed with exit code 1 (use -v to
see invocation)


>> #include <shared_mutex>
>
> I'm guessing Cygwin does not support the functionality declared in the
> headers yet.

If that were the case, it should not compile with g++ -std=c++11,
gnu++14, or gnu++17,
but it does. Also, a much cleaner error message could be shown with:

#error shared_mutex not supported

in the header file, instead of lots of "pthread_rwlock_* not declared
in this scope".

(Note: the first one, with the std::stringstream, still fails with -std=gnu++17)

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