You may define some flags to be passed to tasks at compile time. They will be added to compile line as -DKEY=value on every source file for a given task

Warning

Defined values when compiling a C file are unpredictable if

• This C file is shared between tasks
• The task corresponding to the C-file is instanciated more than once with different defines

If the only purpose is to pass up a numeric value, you should use consts.