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.
This command has been superseded by alternatives:
Flags beginning in
/D that look like preprocessor definitions are
automatically added to the
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
properties for details on adding preprocessor definitions to specific
scopes and configurations.
cmake-buildsystem(7) manual for more on defining