Ported the runtime test to Go. It works in both 32-bit and 64-bit!

darwintest/runtimetest.c

@@ -1,22 +0,0 @@
-// 27 february 2014
-#include <stdio.h>
-#include <objc/message.h>
-#include <objc/objc.h>
-#include <objc/runtime.h>
-
-int main(void)
-{
-	id NSString = objc_getClass("NSString");
-	SEL stringFromUTF8String =
-		sel_getUid("stringWithUTF8String:");
-	id str = objc_msgSend(NSString,
-		stringFromUTF8String,
-		"hello, world\n");
-	SEL UTF8String =
-		sel_getUid("UTF8String");
-
-	printf("%s",
-		(char *) objc_msgSend(str,
-			UTF8String));
-	return 0;
-}

darwintest/runtimetest.go

@@ -0,0 +1,41 @@
+// 27 february 2014
+package main
+
+import (
+	"fmt"
+	"unsafe"
+)
+
+// #cgo LDFLAGS: -lobjc -framework Foundation
+// #include <stdlib.h>
+// #include <objc/message.h>
+// #include <objc/objc.h>
+// #include <objc/runtime.h>
+// /* cgo doesn't handle ... */
+// id objc_msgSend_noargs(id obj, SEL sel) { return objc_msgSend(obj, sel); }
+// id objc_msgSend_strarg(id obj, SEL sel, char *a) { return objc_msgSend(obj, sel, a); }
+import "C"
+
+func main() {
+	_NSString := C.CString("NSString")
+	defer C.free(unsafe.Pointer(_NSString))
+	_stringWithUTF8String := C.CString("stringWithUTF8String:")
+	defer C.free(unsafe.Pointer(_stringWithUTF8String))
+	_UTF8String := C.CString("UTF8String")
+	defer C.free(unsafe.Pointer(_UTF8String))
+	_hello := C.CString("hello, world\n")
+	defer C.free(unsafe.Pointer(_hello))
+
+	NSString := C.objc_getClass(_NSString)
+	stringWithUTF8String :=
+		C.sel_getUid(_stringWithUTF8String)
+	str := C.objc_msgSend_strarg(NSString,
+		stringWithUTF8String,
+		_hello)
+	UTF8String :=
+		C.sel_getUid(_UTF8String)
+	res := C.objc_msgSend_noargs(str,
+			UTF8String)
+	cres := (*C.char)(unsafe.Pointer(res))
+	fmt.Printf("%s", C.GoString(cres))
+}