MantisBT - CMake

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Project

Category

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Date Submitted

Last Update

0015550

CMake

public

2015-05-01 13:26

2015-11-02 09:15

Reporter

Daniel Schepler

Assigned To

Priority

normal

Severity

minor

Reproducibility

always

Status

closed

Resolution

duplicate

Platform

Debian

Linux

OS Version

stretch

Product Version

CMake 3.2.2

Target Version

Fixed in Version

Summary

0015550: check_cxx_source_compiles() does not honor CMAKE_CXX_STANDARD

Description

In a project I recently converted to use set(CMAKE_CXX_STANDARD 11) instead of the previous hard coding of -std=* compile flags in cxx_flag_overrides.cmake, I just noticed that our test for std::unordered_map<> broke.

Steps To Reproduce

set(CMAKE_CXX_STANDARD 11)
check_cxx_source_compiles(
"#include <unordered_map>

int main() {
    std::unordered_map<int, int> m;
    return m.size();
}"
    HAVE_STD_UNORDERED_MAP)

Additional Information

I can work around that with set(CMAKE_REQUIRED_FLAGS ${CMAKE_CXX11_EXTENSION_COMPILE_OPTION}) . That seems a bit ugly, though.

I'm not sure what a proper "fix" to this would be. My ideas would be adding *_STANDARD arguments to try_compile() which might not quite be scalable; or maybe having check_cxx_source_compiles add -DCMAKE_CXX_STANDARD=... to the CMAKE_FLAGS it passes to try_compile(), based on CMAKE_CXX_STANDARD which could be overridden by setting CMAKE_REQUIRED_CXX_STANDARD which also seems like it might not be the best possible solution.