Re: [RFH] CMake: detect if being run via Visual Studio, independent of build generator?

On Sat, May 29, 2021 at 9:55 PM Philip Oakley [off-list ref] wrote:

On 29/05/2021 16:49, Matt Rogers wrote:

quoted

I have some experience at my job with CMake, but some quick testing
has found that adding a check like:

message("MSVC = ${MSVC} , WIN32 = ${WIN32})

shows that the MSVC is uninitialized and WIN322 is initialized.  so the
issue is that the MSVC variable isn't being set which is causing
vcpkg_install.bat to not run, rather than the WIN32 variable.

Thanks for confirming what I'm seeing. It's good to have.

quoted

The msvc variable is intended to be set whenever the compiler is a Visual C/C++
compiler [1].  And it seems like visual studio should be setting that itself
either via a toolchain or some other mechanism.

CMake sets this variable.
Please see {CMAKE_INSTALLATION}/share/cmake-<version>/modules/Platform/Windows-MSVC.cmake.
This happens after CMake is required to find a compiler.
This happens in line:93 where we enable the C language.

To fix this I would suggest to change line:53

-  if(MSVC AND NOT EXISTS ${VCPKG_DIR})
+ if(CMAKE_GENERATOR MATCHES "Visual Studio" AND NOT EXISTS ${VCPKG_DIR})

and
add CMakeSettings.json to force Visual Studio to use MSBuild.
Please see https://docs.microsoft.com/en-us/cpp/build/cmakesettings-reference?view=msvc-160



Thank You,
Sibi Siddharthan