Brad King wrote: > On 09/16/2015 02:22 PM, Stephen Kelly wrote: >>> The default dialect computed with the compiler id may not be the >>> same as the effective default dialect when CMAKE_CXX_FLAGS is >>> considered. >> >> I pushed another fixup which may disable the test in that case, and may >> also disable it with GNU 6 and other compilers with default standard >= >> 11. > > That may fix the trouble for CMake's test suite, but might this > also be a problem for projects in general? Actually this could > be an existing problem whether CMake computes or memorizes the > raw compiler default. If we're making decisions about what flags > to add based on CMAKE_<LANG>_STANDARD_DEFAULT, but the user has > already specified their own -std= flags in CMAKE_<LANG>_FLAGS, > might we end up with the incorrect standard level, or multiple > flags?
Multiple flags, apparently. I made a project with target_compile_features(hello PRIVATE cxx_decltype_auto) # -std=c++14 and built it with GNU 5.1(default dialect 98). I ran cmake with -DCMAKE_CXX_FLAGS=-std=c++11. The result is that a default of 11 is computed (with my branch) for the CXX_STANDARD_DEFAULT because of the CMAKE_CXX_FLAGS=-std=c++11, but 14 is the requirement, so -std=c++11 -std=gnu++14 appears on the command line. The latter 'wins' in this case. If I instead use target_compile_features(hello PRIVATE cxx_static_assert) # -std=c++11 Then -std=c++11 -std=gnu++11 appears instead, which is consistent with the design of CompileFeatures. Arguably the -std=gnu++11 should not be added in that case, but changing that existing behavior would be a different topic. Thanks, Steve. -- 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/mailman/listinfo/cmake-developers
