How to build x86 and/or x64 on Windows from command line with CMAKE?

Question

One way to get cmake to build x86 on Windows with Visual Studio is like so:

1. Start Visual Studio Command prompt for x86
2. Run cmake: cmake -G "NMake Makefiles" \path_to_source\
3. nmake

One way to get cmake to build x64 on Windows with Visual Studio is like so:

1. Start Visual Studio Command prompt for x64
2. Run cmake: cmake -G "NMake Makefiles" \path_to_source\
3. nmake

Using Cmake, how do I compile either or both architectures? (like how Visual Studio does it from in the IDE)

Answer 1

This cannot be done with CMake. You have to generate two separate build folders. One for the x86 NMake build and one for the x64 NMake build. You cannot generate a single Visual Studio project covering both architectures with CMake, either.

To build Visual Studio projects from the command line for both 32-bit and 64-bit without starting a Visual Studio command prompt, use the regular Visual Studio generators.

For CMake 3.13 or newer, run the following commands:

cmake -G "Visual Studio 16 2019" -A Win32 -S \path_to_source\ -B "build32"
cmake -G "Visual Studio 16 2019" -A x64 -S \path_to_source\ -B "build64"
cmake --build build32 --config Release
cmake --build build64 --config Release

For earlier versions of CMake, run the following commands:

mkdir build32 & pushd build32
cmake -G "Visual Studio 15 2017" \path_to_source\
popd
mkdir build64 & pushd build64
cmake -G "Visual Studio 15 2017 Win64" \path_to_source\
popd
cmake --build build32 --config Release
cmake --build build64 --config Release

CMake generated projects that use one of the Visual Studio generators can be built from the command line with using the option --build followed by the build directory. The --config options specifies the build configuration.