[cfe-dev] Which version of libc++ provides C++14 shared_mutex header

Eric Fiselier eric at efcs.ca
Tue Jun 9 09:03:59 PDT 2015

There currently no useful versioning information provided by the
libc++ headers. I hope to change this before 3.7 so that
`_LIBCPP_VERSION` matches the major and minor release version numbers.


On Tue, Jun 9, 2015 at 1:15 AM, Edward Diener
<eldlistmailingz at tropicsoft.com> wrote:
> I asked this question about libc++ on the LLVM developers mailing list but
> since no one had any informatory answer there they suggested I come here.
> I want to determine, for a given _LIBCPP_VERSION of libc++, whether the
> C++14 header file shared_mutex is supported/provided at compile time through
> some sort of predefined macro or combination of macros.
> Since libc++ appears to be independent of clang, gcc, or whatever compiler
> might want to use it as its C++ standard library, I would have expected that
> the optimum way of doing this was to find libc++ documentation that
> explained that for a particular _LIBCPP_VERSION a particular set of header
> files were supported. Or, at the very least, for a particular
> _LIBCPP_VERSION C++03 header files only were supported, for another
> particular _LIBCPP_VERSION C++03 and C++11 header files were supported, for
> another particular _LIBCPP_VERSION C++03, C++11, and C++14 header files were
> supported etc. Or something like that.
> I do know about the clang include file checking macros but I don't know with
> what version of clang I can expect this to work. But given that the include
> file checking macros were introduced in gcc with version 5.1, and given that
> other compilers could potentially be using libc++, I am hoping that there is
> a strictly libc++ solution to my problem.
> If there is not I would like to recommed to the libc++ developers that there
> should be.
> I am working to potentially add support in Boost.config to shared_mutex
> header file detection, and libc++ is one of the standard libraries supported
> by Boost.config. Unfortunately the detection of standard header files for
> Boost.config in libc++ is pretty primitive. Is there any documentation about
> the predefined macros in libc++ which could help us at Boost come up with a
> much better way to determine what libc++ supports and does not support for
> any given release of the library ? If I have missed a discussion or
> discussions about this regarding libc++ please feel free to point me in the
> right direction. My google search regarding libc++ and how to tell what is
> supports for any given release yields almost nothing of value and its
> documentation page at http://libcxx.llvm.org/ does not tell me anything like
> what I want to know either.
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