Enable compiler option "/Zc:__cplusplus" in Visual Studio backends with "/std:c++??" #15528
Description
When using Visual Studio as backend the macro __cplusplus is only set if the compiler option "/Zc:__cplusplus" is enabled.
If you use ninja as backend, the macro is set correctly.
You can reproduce it in this project:
meson.build
project(
'c-version-test',
['cpp'],
version: '1.0.0',
default_options: [
'buildtype=debugoptimized',
'cpp_std=c++17'
]
)
executable(
'c_version_test',
sources: 'main.cpp',
win_subsystem: 'console',
install: true,
)
main.cpp
#include <iostream>
int main()
{
if (__cplusplus >= 201703)
std::cout << "std:c++17" << std::endl;
else
std::cout << "__cplusplus = " << __cplusplus << std::endl;
}
Running this after building with backend ninja you get
std:c++17
After building with backend vs2022 you get
__cplusplus = 199711
After setting
'cpp_std=c++17'
in meson.build I would expect the first output whatever backend I use.
Windows 11 24H2, Visual Studio 2022, meson 1.10.0