setCMAKECXXCOMPILER

setCMAKECXXCOMPILER is not a separate CMake command; the relevant variable is CMAKE_CXX_COMPILER. This variable stores the full path to the C++ compiler that CMake will use for building C++ targets. It is intended to be set before the project is configured, so that CMake can select and configure the build with the desired compiler.

Ways to set it include passing it on the configure command line, using a toolchain file, or assigning it in the top-level CMakeLists.txt before project() is called. Common forms are: cmake -S . -B build -DCMAKE_CXX_COMPILER=/path/to/compiler, or in a toolchain file via set(CMAKE_CXX_COMPILER /path/to/compiler). You can also set it in the CMake cache with FORCE, but this is typically discouraged for routine use.

Notes and caveats: CMAKE_CXX_COMPILER must be set before enabling languages or calling project(). If you set it after CMake has configured the project, the change will not take effect in the current configure; you usually need to reconfigure in a clean build directory. The variable is part of the cache in practice, so changing it may require removing CMakeCache.txt or starting a new build directory to avoid stale state. It is commonly used for cross-compiling or selecting a specific toolchain on multi-compiler systems.

In summary, CMAKE_CXX_COMPILER specifies the C++ compiler CMake uses, and should be configured prior to project() to ensure a consistent and reproducible build.