# add_definitions

Add `-D` define flags to the compilation of source files.

    add_definitions(-DFOO -DBAR ...)

Adds definitions to the compiler command line for targets in the current directory, whether added before or after this command is invoked, and for the ones in sub-directories added after. This command can be used to add any flags, but it is intended to add preprocessor definitions.

Note

This command has been superseded by alternatives:

- Use `add_compile_definitions()` to add preprocessor definitions.

- Use `include_directories()` to add include directories.

- Use `add_compile_options()` to add other options.

Flags beginning in `-D` or `/D` that look like preprocessor definitions are automatically added to the `COMPILE_DEFINITIONS` directory property for the current directory. Definitions with non-trivial values may be left in the set of flags instead of being converted for reasons of backwards compatibility. See documentation of the `directory`, `target`, `source file` `COMPILE_DEFINITIONS` properties for details on adding preprocessor definitions to specific scopes and configurations.

## See Also

- The `cmake-buildsystem(7)` manual for more on defining buildsystem properties.