CMAKECXXCOMPILER

CMAKE_CXX_COMPILER is a CMake variable used to specify the C++ compiler that should be used for building a project. It is a cache variable that holds the path to the C++ compiler executable and can be set by the user through command line options, such as -DCMAKE_CXX_COMPILER, or by editing the CMake cache in an existing build directory.

When configuring a project, CMake relies on this variable to determine the C++ toolchain. If the variable is not provided, CMake attempts to locate a suitable C++ compiler on the system by probing common tools such as g++, clang++, or cl.exe, depending on the platform and available toolchains. The chosen compiler affects supported language features, available standards, and the flags that CMake can generate for the build.

CMAKE_CXX_COMPILER is specific to the C++ language; there is a separate CMAKE_C_COMPILER for C. In multi-language projects, separate compiler variables may be used for each language. The variable also interacts with compiler identification variables such as CMAKE_CXX_COMPILER_ID and CMAKE_CXX_COMPILER_VERSION, which CMake sets after identifying the compiler.

Changing the compiler after an initial configuration typically requires reconfiguring the project or starting a new build directory, since an existing build is tied to the previously detected toolchain. This variable can be used to enable cross-compilation by pointing to a compiler for a target architecture.

Example: cmake -S . -B build -DCMAKE_CXX_COMPILER=/usr/bin/clang++.