On 04/20/2014 03:57 AM, Stephen Kelly wrote: >> Perhaps we can have a feature name like "cxx_std_11" to require a >> given standard level with an error if it is not available. > > Which compilers would provide that feature? GCC 4.8.1 and Clang 3.4 > (complete support)? GCC 4.7 (First release after ratification. Has compile > flag -std=c++11)? GCC 4.3 (Has -std=c++0x)? MSVC? MSVC 2015 (speculative > full support)? MSVC 2010 (partial support)? MSVC 2008 (Has override > keyword)?
Consider a project that writes set(CMAKE_CXX_STANDARD 11) and someone tries to build with a compiler for which CMake does not know about a -std=c++11 flag. Currently CMake generates no error and "decays" to build with no flag at all. Let's say the project happens to build without the flag because the compiler defaults to a hypothetical -std=ext11 flag. Furthermore the project code happens to (unintentionally) depend on that compiler's extensions to c++11 to compile. Everything appears to work. Later CMake learns about the -std=c++11 flag for that compiler and honors the CXX_STANDARD request by passing it. Now the compiler has its extensions disabled and the project fails to build. This was due to an update in CMake, not the project. We need a way for a project to say that it should not build unless CMake knows how to nominally enable support for the given language level. Within that level the project could do its own preprocessor tests or use WriteCompilerDetectionHeader to adapt to the subset of the language level the compiler actually supports. However, when CMake is asked to use a compiler it does not know supports the language level at all, it should be an error. -Brad -- Powered by www.kitware.com Please keep messages on-topic and check the CMake FAQ at: http://www.cmake.org/Wiki/CMake_FAQ Kitware offers various services to support the CMake community. For more information on each offering, please visit: CMake Support: http://cmake.org/cmake/help/support.html CMake Consulting: http://cmake.org/cmake/help/consulting.html CMake Training Courses: http://cmake.org/cmake/help/training.html Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html Follow this link to subscribe/unsubscribe: http://public.kitware.com/cgi-bin/mailman/listinfo/cmake-developers
