Error: functions that differ only in their return type cannot be overloaded

I'm using mac os 10.9, I have a C++ program that uses freeglut library. When I try to make the project. It gives an error which I don't know if it's my fault or not. This is the message:

In file included from /usr/X11/include/GL/freeglut.h:18:
/usr/X11/include/GL/freeglut_ext.h:177:27: error: functions that differ only in their return type cannot be overloaded
FGAPI GLUTproc FGAPIENTRY glutGetProcAddress( const char *procName );

More information: I used CMake (version 2.8.12) to generate the Makefile, and installed the latest version of Xcode and XQuartz.

Any help is appreciated. Thank you.

In glut.h and freeglut_ext.h files:

In glut.h:

#if (GLUT_API_VERSION >= 5)
extern void * APIENTRY glutGetProcAddress(const char *procName) OPENGL_DEPRECATED(10_3, 10_9);
#endif

In freeglut_ext.h:

/*
 * Extension functions, see freeglut_ext.c
 */
typedef void (*GLUTproc)();
FGAPI GLUTproc FGAPIENTRY glutGetProcAddress( const char *procName );

Solution

One of the declarations returns a function type GLUTproc (specifying a function that takes no arguments), and the other declaration returns a pointer (void*). Both functions take the same arguments (a single const char*). What the compiler says is true.

You're only seeing a complaint about "overloading" because it's C++. In C++, if a compiler thinks it's seen two different functions with the same name then each one needs to have different arguments (e.g. a different number of arguments, or distinct types).

In this case, I doubt the functions are meant to be different; they're meant to be the same, and at some point the API evolved and changed the declaration.

You need to find some way to prevent the compiler from seeing both declarations at the same time (perhaps by setting GLUT_API_VERSION). If you have to, you can #include just one of the files and see if you really need the other file (and if you did, you may have to manually declare some things to avoid a 2nd #include).