C code compiled with C++: undefined reference

Question

I have a small program that I can compile with GCC and ICC without any difficulties, but I would also like the code to work with G++ and ICPC. I tried to add this:

Answer 1

You get undefined references because the declaration and the definition are not matching if you put extern "C", which prevents name mangling from happening: but in this case this is happening only in your header files.