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Compile CMake as C++17 if supported by the compiler
Add a check that a simple source file can compile as C++17 that uses some of the features we need. Do this only when hosted by CMake 3.8 or above because those versions are aware of C++17. Check for unordered_map as we do in bootstrap since commit 375eca7 (bootstrap: Check support for unordered_map from compiler mode, 2017-11-30). Also maintain the existing C++14 cstdio check.
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@@ -0,0 +1,36 @@ | ||
set(CMake_CXX17_BROKEN 0) | ||
if(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang") | ||
if(NOT CMAKE_CXX17_STANDARD_COMPILE_OPTION) | ||
set(CMake_CXX17_WORKS 0) | ||
endif() | ||
if(NOT DEFINED CMake_CXX17_WORKS) | ||
message(STATUS "Checking if compiler supports needed C++17 constructs") | ||
try_compile(CMake_CXX17_WORKS | ||
${CMAKE_CURRENT_BINARY_DIR} | ||
${CMAKE_CURRENT_LIST_DIR}/cm_cxx17_check.cpp | ||
CMAKE_FLAGS -DCMAKE_CXX_STANDARD=17 | ||
OUTPUT_VARIABLE OUTPUT | ||
) | ||
if(CMake_CXX17_WORKS AND "${OUTPUT}" MATCHES "error: no member named.*gets.*in the global namespace") | ||
set_property(CACHE CMake_CXX17_WORKS PROPERTY VALUE 0) | ||
endif() | ||
if(CMake_CXX17_WORKS) | ||
message(STATUS "Checking if compiler supports needed C++17 constructs - yes") | ||
file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeOutput.log | ||
"Determining if compiler supports needed C++17 constructs passed with the following output:\n" | ||
"${OUTPUT}\n" | ||
"\n" | ||
) | ||
else() | ||
message(STATUS "Checking if compiler supports needed C++17 constructs - no") | ||
file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log | ||
"Determining if compiler supports needed C++17 constructs failed with the following output:\n" | ||
"${OUTPUT}\n" | ||
"\n" | ||
) | ||
endif() | ||
endif() | ||
if(NOT CMake_CXX17_WORKS) | ||
set(CMake_CXX17_BROKEN 1) | ||
endif() | ||
endif() |
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Original file line number | Diff line number | Diff line change |
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#include <cstdio> | ||
#include <unordered_map> | ||
|
||
int main() | ||
{ | ||
return 0; | ||
} |