The ST_USE_MEMORY constant determines whether memory management functions are included or excluded from compilation. These functions will be compiled if the value is set to 1. If the value is set to 0, they will not be compiled.

If this constant is not defined, it defaults to 1, causing the functions to be included in the output code. If memory management functions are not required (e.g., when using standard C library functions), they can be excluded by setting ST_USE_MEMORY to 0, thereby reducing the output code size.