88 lines
2.9 KiB
CMake
88 lines
2.9 KiB
CMake
# Detect if compiler version is sufficient for supporting C++17.
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# If it is, CMAKE_CXX_FLAGS are modified appropriately and HAVE_CXX17
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# is set to a true value. Else, CMake exits with a fatal error message.
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# This currently only works for GCC and Clang compilers.
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# In Cmake 3.8+, CMAKE_CXX_STANDARD_REQUIRED should be able to replace
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# all the logic below.
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if (DEFINED HAVE_CXX17)
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return()
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endif ()
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set(required_gcc_version 8.0)
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set(required_clang_version 9.0)
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set(required_msvc_version 19.14)
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set(required_apple_clang_version 11.4)
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if (MSVC)
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if (CMAKE_CXX_COMPILER_VERSION VERSION_LESS ${required_msvc_version})
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message(
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FATAL_ERROR
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"MSVC version must be at least "
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"${required_gcc_version} for C++17 support, detected: "
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"${CMAKE_CXX_COMPILER_VERSION}")
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endif ()
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set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /std:c++17")
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set(HAVE_CXX17 true)
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return()
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endif ()
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include(CheckCXXSourceCompiles)
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set(cxx17_testcode "#include <optional>
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int main() { std::optional<int> a; }")
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check_cxx_source_compiles("${cxx17_testcode}" cxx17_already_works)
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if (cxx17_already_works)
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# Nothing to do. Flags already select a suitable C++ version.
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set(HAVE_CXX17 true)
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return()
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endif ()
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set(cxx17_flag "-std=c++17")
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if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
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if (CMAKE_CXX_COMPILER_VERSION VERSION_LESS ${required_gcc_version})
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message(
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FATAL_ERROR
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"GCC version must be at least "
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"${required_gcc_version} for C++17 support, detected: "
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"${CMAKE_CXX_COMPILER_VERSION}")
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endif ()
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elseif (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
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if (CMAKE_CXX_COMPILER_VERSION VERSION_LESS ${required_clang_version})
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message(
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FATAL_ERROR
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"Clang version must be at least "
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"${required_clang_version} for C++17 support, detected: "
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"${CMAKE_CXX_COMPILER_VERSION}")
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endif ()
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if (CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5)
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set(cxx17_flag "-std=c++1z")
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endif ()
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elseif (CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang")
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if (CMAKE_CXX_COMPILER_VERSION VERSION_LESS ${required_apple_clang_version})
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message(
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FATAL_ERROR
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"Apple Clang version must be at least "
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"${required_apple_clang_version} for C++17 support, detected: "
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"${CMAKE_CXX_COMPILER_VERSION}")
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endif ()
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else ()
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# Unrecognized compiler: fine to be permissive of other compilers as long
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# as they are able to support C++17 and can compile the test program, but
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# we just won't be able to give specific advice on what compiler version a
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# user needs in the case it actually doesn't support C++17.
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endif ()
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set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${cxx17_flag}")
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check_cxx_source_compiles("${cxx17_testcode}" cxx17_works)
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if (NOT cxx17_works)
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message(FATAL_ERROR "failed using C++17 for compilation")
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endif ()
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set(HAVE_CXX17 true)
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