the C++ standard used by a CMake project is specified by CMAKE_CXX_STANDARD, but if this variable is not specified, the default standard used by the compiler is used. at the moment of writing, GCC-14.2 uses C++17 as its default C++ standard. but Seastar by default uses the highest C++ standard supported by the configured compiler. and it is C++23 for GCC-14.2.
in 52dab12a, we added the compatibility checks to avoid the build failure caused by the discrepancies between different compilers and the different C++ standards. and let CMake warn at seeing different compilers or different C++ standands used when building Seastar and its parent project.
in the sample, we didn't specify the C++ standard. so user is very likely to run into the build failure reported by #2181, where the Seastar library was compiled using C++23, while the Seastar application is compiled using C++17.
in this change, we specify CMAKE_CXX_STANDARD explicitly to avoid this confusion.
the C++ standard used by a CMake project is specified by
CMAKE_CXX_STANDARD, but if this variable is not specified, the default standard used by the compiler is used. at the moment of writing, GCC-14.2 uses C++17 as its default C++ standard. but Seastar by default uses the highest C++ standard supported by the configured compiler. and it is C++23 for GCC-14.2.in 52dab12a, we added the compatibility checks to avoid the build failure caused by the discrepancies between different compilers and the different C++ standards. and let CMake warn at seeing different compilers or different C++ standands used when building Seastar and its parent project.
in the sample, we didn't specify the C++ standard. so user is very likely to run into the build failure reported by #2181, where the Seastar library was compiled using C++23, while the Seastar application is compiled using C++17.
in this change, we specify
CMAKE_CXX_STANDARDexplicitly to avoid this confusion.