Simple linking problem

[Matthew Woehlke]

gccNewbie wrote:
> So it is really a very simple riddle. 'gcc -lmylib mysource.c' uses a
> function 'foo' which nm shows is defined in libmylib.a. gcc does not
> complain about not being able to find mylib, but it does complain that 'foo'
> is an 'undefined reference'. In what situation could that happen?

Linux lets you get away with this wrong link order due to lazy symbol 
resolution, whereas Windows does not. What you have done is asked to 
first link to libmylib. Since no objects (actually, you don't *have* any 
objects yet!) require any symbols from libmylib, no symbols are 
imported. Next you have asked to link 'mysource.c' (which is first 
compiled to object form, of course), which has unresolved symbols. And 
now you are at the end of the link step with unresolved symbols, which 
are not permitted on Windows.

The correct order is to first compile/link 'mysource.c', which (as 
expected) has unresolved symbols, and /then/ to link 'libmylib' which 
contains the unresolved symbols. Now when you reach the end of the list 
of things to link, you do not have unresolved symbols, and so you can 
successfully produce a binary.

-- 
Matthew
"Ah, yes. Control the media and you control the world."
   -- from a story by Raven Blackmane