Some reusable routines may be compiled into a library, see the documentation
for the assembler and linkage editor (which are in <installdir>/share/sdcc/doc)
for how to create a .lib library file. Libraries
created in this manner can be included in the command line. Make sure
you include the -L <library-path> option to tell the linker where
to look for these files if they are not in the current directory.
Here is an example, assuming you have the source file foomain.c
and a library foolib.lib in the directory mylib (if
that is not the same as your current project):
sdcc foomain.c foolib.lib -L mylib
Note here that mylib must be an absolute path name.
The most efficient way to use libraries is to keep separate modules
in separate source files. The lib file now should name all the modules.rel
files. For an example see the standard library file libsdcc.lib
in the directory <installdir>/share/lib/small.