func main() {
// Simple C function call.
C.f0()
// Call with constant.
C.f1(5)
// Call with Go int - cast to C int.
var i int = 8
C.f1(C.int(i))
// Convert Go string to C string (char*) and back.
cs := C.CString("Go string")
csRet := C.f2(cs)
fmt.Printf("fmt: %s\n", C.GoString(csRet))
C.free(unsafe.Pointer(cs)) // free memory right now ...
defer C.free(unsafe.Pointer(csRet)) // ... or later
// Pass C struct to C function by value.
s1 := C.struct_s1{a: 5} // or cast with C.int: s1 := C.struct_s1{C.int(i)}
s1Ret := C.f31(s1)
fmt.Printf("f31: s1=%v, s1Ret=%v\n", s1, s1Ret)
// Pass C struct to C function by pointer.
s1 = C.struct_s1{a: 5}
s1Ret = *C.f32(&s1)
fmt.Printf("f32: s1=%v, s1Ret=%v\n", s1, s1Ret)
// Pass C struct with int pointer to C function.
// s2 := C.struct_s2{&C.int(i)} - compile error "cannot take the address of _Ctype_int(i)", create variable as below
ci := C.int(i)
s2 := C.struct_s2{p: &ci}
fmt.Printf("s2=%v, *s2.p=%d, i=%d\n", s2, *s2.p, i)
C.f4(s2)
fmt.Printf("f4: s2=%v, *s2.p=%d, i=%d\n", s2, *s2.p, i)
// Pass C function pointer to C function.
// C.f5(C.f1) - compile error "must call C.f1"
// fp := unsafe.Pointer(C.f1) - compile error "must call C.f1"
// It is not possible to pass C function pointer via Go.
// Pass C function pointer to C function with simple C wrapper (see top of this file).
C.call_f5_with_f1()
// Pass Go function pointer to C function.
f := func(i C.int) {
fmt.Println("Go f()")
}
fp := unsafe.Pointer(&f)
// C.f5((*[0]byte)(fp)) - Compiles but explodes. Do not do this!
// Pass global Go function pointer to C function.
f = F
fp = unsafe.Pointer(&f)
// C.f5((*[0]byte)(fp)) - Compiles but explodes. Do not do this!
// It is possible to call Go function from C. See main2.go for solution.
_ = fp
}
func CrashTraceback() {
runtime.SetCgoTraceback(0, unsafe.Pointer(C.cgoTraceback), nil, unsafe.Pointer(C.cgoSymbolizer))
C.f1()
}