CMAKEBUILDTYPE

CMAKE_BUILD_TYPE is a CMake cache variable used by single-configuration generators to select a build configuration during the configure step. It affects which per-configuration compiler and linker flags are applied, by choosing among configuration-specific variables such as CMAKE_C_FLAGS_DEBUG, CMAKE_C_FLAGS_RELEASE, CMAKE_CXX_FLAGS_DEBUG, and similar for other languages. The typical, standard values are Debug, Release, RelWithDebInfo, and MinSizeRel, though projects may define additional or custom types.

Usage and impact: When configuring a project, you usually pass -DCMAKE_BUILD_TYPE=<type> to CMake, for example cmake -DCMAKE_BUILD_TYPE=Release .. This sets up the appropriate flags and settings for the chosen configuration for single-configuration generators like Unix Makefiles or Ninja. The build then uses those flags when compiling and linking.

Generators and scope: CMAKE_BUILD_TYPE does not apply to multi-configuration generators such as Visual Studio or Xcode, where the active configuration is selected at build time inside the IDE or with a --config option to cmake --build. For these generators, CMAKE_CONFIGURATION_TYPES defines the available configurations, and the actual build configuration is chosen independently of CMAKE_BUILD_TYPE.

Notes: If CMAKE_BUILD_TYPE is not set for a single-configuration generator, no configuration-specific flags are automatically selected unless the project provides defaults. In practice, developers often configure separate build trees for different configurations (e.g., Debug and Release) or rely on multi-configuration generators when building across configurations in one environment.