feat(cgo): support pointer args in Call

Co-Authored-By: Virgil <virgil@lethean.io>

call_test.go

@@ -177,6 +177,20 @@ func TestCallSupportsCUintptrArgument(t *testing.T) {
 	}
 }
 
+func TestCallSupportsArbitraryPointerArgument(t *testing.T) {
+	t.Parallel()
+
+	payload := []byte("agent")
+	if err := Call(callAnyPointerArgumentFunction(), &payload[0]); err != nil {
+		t.Fatalf("expected success for pointer argument, got %v", err)
+	}
+
+	var pointer *byte
+	if err := Call(callAnyPointerArgumentFunction(), pointer); err == nil {
+		t.Fatal("expected error for nil pointer argument")
+	}
+}
+
 func TestCallSupportsByteSliceArgument(t *testing.T) {
 	t.Parallel()
 

call_test_support.go

@@ -90,6 +90,10 @@ int call_uintptr_argument(uintptr_t value) {
     return value == 42 ? 0 : 13;
 }
 
+int call_any_pointer_argument(uintptr_t value) {
+    return value == 0 ? 13 : 0;
+}
+
 uintptr_t call_sum_length_ptr(void) {
     return (uintptr_t)&call_sum_length;
 }
@@ -146,6 +150,10 @@ uintptr_t call_uintptr_argument_ptr(void) {
     return (uintptr_t)&call_uintptr_argument;
 }
 
+uintptr_t call_any_pointer_argument_ptr(void) {
+    return (uintptr_t)&call_any_pointer_argument;
+}
+
 */
 import "C"
 
@@ -221,6 +229,11 @@ func callCUintptrArgumentFunction() unsafe.Pointer {
 	return *(*unsafe.Pointer)(unsafe.Pointer(&function))
 }
 
+func callAnyPointerArgumentFunction() unsafe.Pointer {
+	function := C.call_any_pointer_argument_ptr()
+	return *(*unsafe.Pointer)(unsafe.Pointer(&function))
+}
+
 func callWithErrnoZero() (int, error) {
 	return WithErrno(func() C.int {
 		return 0

string_conversion.go

@@ -811,6 +811,11 @@ func toSyscallArg(value interface{}) (uintptr, bool) {
 	default:
 		reflected := reflect.ValueOf(value)
 		switch reflected.Kind() {
+		case reflect.Pointer, reflect.UnsafePointer:
+			if reflected.IsNil() {
+				return 0, true
+			}
+			return reflected.Pointer(), true
 		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
 			return uintptr(reflected.Int()), true
 		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr: