I'd like to port some code from PureC to Gcc.
I know what to do about C files, but I have also some S files where I do not know what to do.
Any advice?
It depends what do you want to "do". You can rewrite the preprocessor directives (section text -> .text, local labels, etc -- fair amount of them is already supported by gnu as) or you can use vasm (compatible with devpac/pure asm) -- it produces a.out output, compatible with gnu linker.