I\'ve been developing a school project in XCode. The final product has to be submitted in source code with a makefile, so I wrote a makefile and to start compiling that way,
To link C++ code, you need to use the g++ command, not the gcc command.
When compiling, the gcc command knows that it's compiling C++ code because of the .cpp suffix (but it's a good idea to use the g++ command anyway).
When linking, the gcc command just sees a bunch of .o files. The g++ command differs from the gcc command in that it knows where to find the C++-specific libraries.
(The fact that the name gcc refers both to the command, which is usually used to compile C code, and the "GNU Compiler Collection" as a whole, can be a little confusing.)