etc/config/windows/fun_present_check.cpp

extern "C"
{
    typedef void (*funptr_t)();
}

// take the address of the function in a way
// that foils even clever optimizers

union {
    funptr_t      pf;
    unsigned long ul;
} funptri;

#ifdef CHECK_DECL

#  if defined (__linux__) && defined (__GNUG__) && __GNUG__ < 3
     // prevent empty exception specifications from triggering
     // gcc 2.9x -fhonor-std link errors looking for std::terminate()
#    include <features.h>
#    undef __THROW
#    define __THROW
#  endif   // gcc < 3 on Linux

#  include HDRNAME

#  ifndef NONAMESPACE

namespace std { }
using namespace std;

#  endif   // NONAMESPACE

int main (int argc, char**)
{
    // with gcc, prevent intrinsics from causing false positives

#  if TAKE_ADDR

    funptri.pf = (funptr_t)&FUNNAME;

    return (argc < 1 ? !funptri.ul : !!funptri.ul) + 0;
    
#  else   // if !TAKE_ADDR

    // disable warnings about an unused variable
    (void)&argc;

    // call the function using the supplied arguments
    #ifdef FUN_PARAMS
        FUN_PARAMS;
    #endif
    (void)FUN;

    return 0;

#  endif   // TAKE_ADDR

}

#else   // if !defined (CHECK_DECL)

extern "C" void FUNNAME ();

int main (int argc, char**)
{
    funptri.pf = (funptr_t)&FUNNAME;

    return (argc < 1 ? !funptri.ul : !!funptri.ul) + 0;
}

#endif   // CHECK_DECL