If you have multiple relocatable DLLs loaded by your application, you must
be VERY careful about the order of libraries being linked by ld. If you
follow the same order as in the "specs" file, you should be ok. 

Here're are simple rules of thumb:

simple C app:
  LIBS = -lmingw32 -lgcc -lmoldnames -lcrtdll -lkernel32

simple C app that needs USER32.DLL:
  LIBS = -luser32 -lmingw32 -lgcc -lmoldnames -lcrtdll -lkernel32

C++ DLLs:
  LIBS = -lstdc++ -lmingw32 -lgcc -lmoldnames -lcrtdll -lkernel32

C++ DLLs that need USER32.DLL:
  LIBS = -luser32 -lstdc++ -lmingw32 -lgcc -lmoldnames -lcrtdll -lkernel32
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
you get the picture, right ;-) The critical sub-sequence order is marked
with ^^ above. Oh yes, another thing -- never link in kernel32 more than
once.

Of course, you can use 'gcc -dll' or 'c++ -dll' to have the libraries
supplied automatically by gcc/c++ etc, so you'd never have to worry about
library names (other than extra ones, such as -luser32 or -ladvap32 etc)
or the link order.