Author: asiri Date: Mon Jan 16 06:44:08 2017 New Revision: 292108 URL: http://llvm.org/viewvc/llvm-project?rev=292108&view=rev Log: [libcxx] Improve design documentation for the external-thread-library configuration
NFC. Differential revision: https://reviews.llvm.org/D28610 Reviewers: EricWF Modified: libcxx/trunk/docs/DesignDocs/ThreadingSupportAPI.rst Modified: libcxx/trunk/docs/DesignDocs/ThreadingSupportAPI.rst URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/docs/DesignDocs/ThreadingSupportAPI.rst?rev=292108&r1=292107&r2=292108&view=diff ============================================================================== --- libcxx/trunk/docs/DesignDocs/ThreadingSupportAPI.rst (original) +++ libcxx/trunk/docs/DesignDocs/ThreadingSupportAPI.rst Mon Jan 16 06:44:08 2017 @@ -33,13 +33,22 @@ interface normally provided by ``<__thre External Threading Library ========================== -Normally ``<__threading_support>`` provides inline definitions to each internal -threading API function it declares. However libc++ also supports using an -external library to provide the definitions. +libc++ can be compiled with its internal threading API delegating to an external +library. Such a configuration is useful for library vendors who wish to +distribute a thread-agnostic libc++ library, where the users of the library are +expected to provide the implementation of the libc++ internal threading API. -When ``_LIBCPP_HAS_THREAD_LIBRARY_EXTERNAL`` libc++ does not provide inline -definitions for the internal API, instead assuming the definitions will be -provided by an external library. +On a production setting, this would be achieved through a custom +``<__external_threading>`` header, which declares the libc++ internal threading +API but leaves out the implementation. + +The ``-DLIBCXX_BUILD_EXTERNAL_THREAD_LIBRARY`` option allows building libc++ in +such a configuration while allowing it to be tested on a platform that supports +any of the threading systems (e.g. pthread) supported in ``__threading_support`` +header. Therefore, the main purpose of this option is to allow testing of this +particular configuration of the library without being tied to a vendor-specific +threading system. This option is only meant to be used by libc++ library +developers. Threading Configuration Macros ============================== _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
