Factor out the code to find gcc, and add a command-line option to override the default executable name. This should help cross-compilation by allowing a cross-gcc to be specified from the configuration file instead of only through the CC environment variable.

extern(C) int printf(char*, ...);

class A
{
    int i;
    void f()
    {
        printf("A.f\n");
    }
}

class B : A
{
    long l;
    void f()
    {
        printf("B.f\n");
    }
}

void main()
{
    A a = new B;
    a.f();
}