Calling C from C++

hello.c

#include <stdio.h>
#include "hello.h"

void hello(int repeatCount) {
    int i;
    for (i = 0; i < repeatCount; i++) {
        printf("hello from C\n");
    }
}

main.cpp

extern "C" void hello(int repeatCount);

int main(int argc, char** argv) {
	hello(3);
}

In order to make the C function callable from C++, the C++ code needed to have a prototype where the function was marked as "extern C" to prevent name mangling. Normally, a C++ function's name would be mangled by the compiler to encode the return type and the argument types, allowing unique names at the assembly code level while allowing the same name to be overloaded at the source code level.