... not only keeps track of function names but also the type of a name. In your case, there is no mod_a_sub_a defined (normally marked 't') in mod_c.o, it's probably a stub mod_b_sub_a ('U') in the ojbect file, do a 'nm' to see what's going on. Also you can experiment by creating a real mod_a_sub_a in mod_c.o, in which case I expect the linker to issue a name ambiguity error. Fei...

.... A linker not only keeps track of function names but also the type of a name. In your case, there is no mod_a_sub_a defined (normally marked 't') in mod_c.o, it's probably a stub mod_b_sub_a ('U') in the ojbect file, do a 'nm' to see what's going on. Also you can experiment by creating a real mod_a_sub_a in mod_c.o, in which case I expect the linker to issue a name ambiguity error. Fei