Often times it is useful to construct a string visible to the pre-compiler and assemble it from one more more other values, defined by means of a #define dierctive. Here’s some example code (this is some custom environemnt config for U-Boot for a STM-based device I work with):

#if defined( DEVELOPER_ALAN ) #define CONFIG_ETHADDR 00:23:b0:00:00:00 […]