can you provide the ACTUAL function declaration? can you provide the ACTUAL full error message? it just seems like you're asking for help without providing all of the relevant information. I'm surprised that nobody has said anything before. it's likely an extern "C" sort of thing, but we won't know until you give us more relevant info. also, if you don't have the source, but only the .o of one of the objects, you can maybe use objdump or nm to list the symbols in the .o file. you could then use that list to figure out why you're getting the error.