Conceptually, the Compiler & Linker are separate tools.

In some products, they are separate executables; eg Keil has a separate C51.exe (compiler) and BL51.exe or LK51.exe (linkers)

On UNIX systems, it is common for a single command to invoke the Compiler, the Linker, or both! This seems to be the model followed by SDCC.

However, SDCC can only Compiler a single source file at a time - see:

http://sdcc.sourceforge.net/doc/sdccm...ode42.html

So, to compile multiple source files, either:

sdcc -c file-1.c                          -- just compile file-1.c to file-1.rel
sdcc -c file-2.c                          -- just compile file-2.c to file-2.rel
:
sdcc -c file-n.c                          -- just compile file-n.c to file-n.rel

sdcc file-1.rel file-2.rel ... file-n.rel -- link all the objects together

Or:

sdcc -c file-1.c                          -- just compile file-1.c to file-1.rel
sdcc -c file-2.c                          -- just compile file-2.c to file-2.rel
:

sdcc file-n.c file-1.rel file-2.rel ... -- compile file-1.c and link with all the other objects

Because the Listing files are the result of the Compilation process - hence they only reflect the individual source files in isolation.
Also, because they reflect the un-linked, relocatable object files, external references are not completed