The -xassembler-with-cpp
option allows you to specify
that all assembly source files need to be preprocessed, irrespective of the source file’s
extension. For example:
xc8-cc
-mcpu=18f4520 -xassembler-with-cpp proj.c init.s
will tell the compiler to run the preprocessor over the assembly source file, even though the file name does not use a .S extension.