all: struct return fixes (#221)

On amd64, there was a crash when calling objc.Send with a struct return type. This was due to calling the wrong objc message send function.

On arm64, if a struct return contained structs that only contained floats it would expect it to be in R8 instead of the expected float registers

Closes #223

Author: TotallyGamerJet

func.go

@@ -250,7 +250,8 @@ func RegisterFunc(fptr interface{}, cfn uintptr) {
 				keepAlive = append(keepAlive, val)
 				addInt(val.Pointer())
 			} else if runtime.GOARCH == "arm64" && outType.Size() > maxRegAllocStructSize {
-				if !isAllSameFloat(outType) || outType.NumField() > 4 {
+				isAllFloats, numFields := isAllSameFloat(outType)
+				if !isAllFloats || numFields > 4 {
 					val := reflect.New(outType)
 					keepAlive = append(keepAlive, val)
 					syscall.arm64_r8 = val.Pointer()
@@ -351,20 +352,34 @@ func RegisterFunc(fptr interface{}, cfn uintptr) {
 // maxRegAllocStructSize is the biggest a struct can be while still fitting in registers.
 // if it is bigger than this than enough space must be allocated on the heap and then passed into
 // the function as the first parameter on amd64 or in R8 on arm64.
+//
+// If you change this make sure to update it in objc_runtime_darwin.go
 const maxRegAllocStructSize = 16
 
-func isAllSameFloat(ty reflect.Type) bool {
-	first := ty.Field(0).Type.Kind()
+func isAllSameFloat(ty reflect.Type) (allFloats bool, numFields int) {
+	allFloats = true
+	root := ty.Field(0).Type
+	for root.Kind() == reflect.Struct {
+		root = root.Field(0).Type
+	}
+	first := root.Kind()
 	if first != reflect.Float32 && first != reflect.Float64 {
-		return false
+		allFloats = false
 	}
 	for i := 0; i < ty.NumField(); i++ {
-		f := ty.Field(i)
-		if f.Type.Kind() != first {
-			return false
+		f := ty.Field(i).Type
+		if f.Kind() == reflect.Struct {
+			var structNumFields int
+			allFloats, structNumFields = isAllSameFloat(f)
+			numFields += structNumFields
+			continue
+		}
+		numFields++
+		if f.Kind() != first {
+			allFloats = false
 		}
 	}
-	return true
+	return allFloats, numFields
 }
 
 func checkStructFieldsSupported(ty reflect.Type) {

objc/objc_runtime_darwin.go

@@ -11,6 +11,7 @@ import (
 	"math"
 	"reflect"
 	"regexp"
+	"runtime"
 	"unicode"
 	"unsafe"
 
@@ -20,28 +21,30 @@ import (
 // TODO: support try/catch?
 // https://stackoverflow.com/questions/7062599/example-of-how-objective-cs-try-catch-implementation-is-executed-at-runtime
 var (
-	objc_msgSend_fn           uintptr
-	objc_msgSend              func(obj ID, cmd SEL, args ...interface{}) ID
-	objc_msgSendSuper2_fn     uintptr
-	objc_msgSendSuper2        func(super *objc_super, cmd SEL, args ...interface{}) ID
-	objc_getClass             func(name string) Class
-	objc_getProtocol          func(name string) *Protocol
-	objc_allocateClassPair    func(super Class, name string, extraBytes uintptr) Class
-	objc_registerClassPair    func(class Class)
-	sel_registerName          func(name string) SEL
-	class_getSuperclass       func(class Class) Class
-	class_getInstanceVariable func(class Class, name string) Ivar
-	class_getInstanceSize     func(class Class) uintptr
-	class_addMethod           func(class Class, name SEL, imp IMP, types string) bool
-	class_addIvar             func(class Class, name string, size uintptr, alignment uint8, types string) bool
-	class_addProtocol         func(class Class, protocol *Protocol) bool
-	ivar_getOffset            func(ivar Ivar) uintptr
-	ivar_getName              func(ivar Ivar) string
-	object_getClass           func(obj ID) Class
-	object_getIvar            func(obj ID, ivar Ivar) ID
-	object_setIvar            func(obj ID, ivar Ivar, value ID)
-	protocol_getName          func(protocol *Protocol) string
-	protocol_isEqual          func(p *Protocol, p2 *Protocol) bool
+	objc_msgSend_fn             uintptr
+	objc_msgSend_stret_fn       uintptr
+	objc_msgSend                func(obj ID, cmd SEL, args ...interface{}) ID
+	objc_msgSendSuper2_fn       uintptr
+	objc_msgSendSuper2_stret_fn uintptr
+	objc_msgSendSuper2          func(super *objc_super, cmd SEL, args ...interface{}) ID
+	objc_getClass               func(name string) Class
+	objc_getProtocol            func(name string) *Protocol
+	objc_allocateClassPair      func(super Class, name string, extraBytes uintptr) Class
+	objc_registerClassPair      func(class Class)
+	sel_registerName            func(name string) SEL
+	class_getSuperclass         func(class Class) Class
+	class_getInstanceVariable   func(class Class, name string) Ivar
+	class_getInstanceSize       func(class Class) uintptr
+	class_addMethod             func(class Class, name SEL, imp IMP, types string) bool
+	class_addIvar               func(class Class, name string, size uintptr, alignment uint8, types string) bool
+	class_addProtocol           func(class Class, protocol *Protocol) bool
+	ivar_getOffset              func(ivar Ivar) uintptr
+	ivar_getName                func(ivar Ivar) string
+	object_getClass             func(obj ID) Class
+	object_getIvar              func(obj ID, ivar Ivar) ID
+	object_setIvar              func(obj ID, ivar Ivar, value ID)
+	protocol_getName            func(protocol *Protocol) string
+	protocol_isEqual            func(p *Protocol, p2 *Protocol) bool
 )
 
 func init() {
@@ -53,6 +56,16 @@ func init() {
 	if err != nil {
 		panic(fmt.Errorf("objc: %w", err))
 	}
+	if runtime.GOARCH == "amd64" {
+		objc_msgSend_stret_fn, err = purego.Dlsym(objc, "objc_msgSend_stret")
+		if err != nil {
+			panic(fmt.Errorf("objc: %w", err))
+		}
+		objc_msgSendSuper2_stret_fn, err = purego.Dlsym(objc, "objc_msgSendSuper2_stret")
+		if err != nil {
+			panic(fmt.Errorf("objc: %w", err))
+		}
+	}
 	purego.RegisterFunc(&objc_msgSend, objc_msgSend_fn)
 	objc_msgSendSuper2_fn, err = purego.Dlsym(objc, "objc_msgSendSuper2")
 	if err != nil {
@@ -104,12 +117,22 @@ func (id ID) SetIvar(ivar Ivar, value ID) {
 	object_setIvar(id, ivar, value)
 }
 
+// keep in sync with func.go
+const maxRegAllocStructSize = 16
+
 // Send is a convenience method for sending messages to objects that can return any type.
 // This function takes a SEL instead of a string since RegisterName grabs the global Objective-C lock.
 // It is best to cache the result of RegisterName.
 func Send[T any](id ID, sel SEL, args ...any) T {
 	var fn func(id ID, sel SEL, args ...any) T
-	purego.RegisterFunc(&fn, objc_msgSend_fn)
+	var zero T
+	if runtime.GOARCH == "amd64" &&
+		reflect.ValueOf(zero).Kind() == reflect.Struct &&
+		reflect.ValueOf(zero).Type().Size() > maxRegAllocStructSize {
+		purego.RegisterFunc(&fn, objc_msgSend_stret_fn)
+	} else {
+		purego.RegisterFunc(&fn, objc_msgSend_fn)
+	}
 	return fn(id, sel, args...)
 }
 
@@ -141,7 +164,14 @@ func SendSuper[T any](id ID, sel SEL, args ...any) T {
 		superClass: id.Class(),
 	}
 	var fn func(objcSuper *objc_super, sel SEL, args ...any) T
-	purego.RegisterFunc(&fn, objc_msgSendSuper2_fn)
+	var zero T
+	if runtime.GOARCH == "amd64" &&
+		reflect.ValueOf(zero).Kind() == reflect.Struct &&
+		reflect.ValueOf(zero).Type().Size() > maxRegAllocStructSize {
+		purego.RegisterFunc(&fn, objc_msgSendSuper2_stret_fn)
+	} else {
+		purego.RegisterFunc(&fn, objc_msgSendSuper2_fn)
+	}
 	return fn(super, sel, args...)
 }
 

objc/objc_runtime_darwin_test.go

@@ -117,3 +117,39 @@ func TestSend(t *testing.T) {
 		t.Failed()
 	}
 }
+
+func ExampleSend() {
+	type NSRange struct {
+		Location, Range uint
+	}
+	class_NSString := objc.GetClass("NSString")
+	sel_stringWithUTF8String := objc.RegisterName("stringWithUTF8String:")
+
+	fullString := objc.ID(class_NSString).Send(sel_stringWithUTF8String, "Hello, World!\x00")
+	subString := objc.ID(class_NSString).Send(sel_stringWithUTF8String, "lo, Wor\x00")
+
+	r := objc.Send[NSRange](fullString, objc.RegisterName("rangeOfString:"), subString)
+
+	fmt.Println(r)
+
+	// Output: {3 7}
+}
+
+func ExampleSendSuper() {
+	super := objc.AllocateClassPair(objc.GetClass("NSObject"), "SuperObject2", 0)
+	super.AddMethod(objc.RegisterName("doSomething"), objc.NewIMP(func(self objc.ID, _cmd objc.SEL) int {
+		return 16
+	}), "i@:")
+	super.Register()
+
+	child := objc.AllocateClassPair(super, "ChildObject2", 0)
+	child.AddMethod(objc.RegisterName("doSomething"), objc.NewIMP(func(self objc.ID, _cmd objc.SEL) int {
+		return 24
+	}), "i@:")
+	child.Register()
+
+	res := objc.SendSuper[int](objc.ID(child).Send(objc.RegisterName("new")), objc.RegisterName("doSomething"))
+
+	fmt.Println(res)
+	// Output: 16
+}

struct_arm64.go

@@ -16,17 +16,17 @@ func getStruct(outType reflect.Type, syscall syscall15Args) (v reflect.Value) {
 		return reflect.New(outType).Elem()
 	case outSize <= 8:
 		r1 := syscall.a1
-		if isAllSameFloat(outType) {
+		if isAllFloats, numFields := isAllSameFloat(outType); isAllFloats {
 			r1 = syscall.f1
-			if outType.NumField() == 2 {
+			if numFields == 2 {
 				r1 = syscall.f2<<32 | syscall.f1
 			}
 		}
 		return reflect.NewAt(outType, unsafe.Pointer(&struct{ a uintptr }{r1})).Elem()
 	case outSize <= 16:
 		r1, r2 := syscall.a1, syscall.a2
-		if isAllSameFloat(outType) {
-			switch outType.NumField() {
+		if isAllFloats, numFields := isAllSameFloat(outType); isAllFloats {
+			switch numFields {
 			case 4:
 				r1 = syscall.f2<<32 | syscall.f1
 				r2 = syscall.f4<<32 | syscall.f3
@@ -42,8 +42,8 @@ func getStruct(outType reflect.Type, syscall syscall15Args) (v reflect.Value) {
 		}
 		return reflect.NewAt(outType, unsafe.Pointer(&struct{ a, b uintptr }{r1, r2})).Elem()
 	default:
-		if isAllSameFloat(outType) && outType.NumField() <= 4 {
-			switch outType.NumField() {
+		if isAllFloats, numFields := isAllSameFloat(outType); isAllFloats && numFields <= 4 {
+			switch numFields {
 			case 4:
 				return reflect.NewAt(outType, unsafe.Pointer(&struct{ a, b, c, d uintptr }{syscall.f1, syscall.f2, syscall.f3, syscall.f4})).Elem()
 			case 3:

struct_test.go

@@ -585,6 +585,18 @@ func TestRegisterFunc_structReturns(t *testing.T) {
 			t.Fatalf("ReturnFourDoubles returned %+v wanted %+v", ret, expected)
 		}
 	}
+	{
+		type FourDoublesInternal struct {
+			f struct{ a, b float64 }
+			g struct{ c, d float64 }
+		}
+		var ReturnFourDoublesInternal func(a, b, c, d float64) FourDoublesInternal
+		purego.RegisterLibFunc(&ReturnFourDoublesInternal, lib, "ReturnFourDoublesInternal")
+		expected := FourDoublesInternal{f: struct{ a, b float64 }{a: 1, b: 2}, g: struct{ c, d float64 }{c: 3, d: 4}}
+		if ret := ReturnFourDoublesInternal(1, 2, 3, 4); ret != expected {
+			t.Fatalf("ReturnFourDoublesInternal returned %+v wanted %+v", ret, expected)
+		}
+	}
 	{
 		type FiveDoubles struct{ a, b, c, d, e float64 }
 		var ReturnFiveDoubles func(a, b, c, d, e float64) FiveDoubles

testdata/structtest/structreturn_test.c

@@ -129,6 +129,20 @@ struct FourDoubles ReturnFourDoubles(double a, double b, double c, double d) {
     return e;
 }
 
+struct FourDoublesInternal{
+    struct {
+        double a, b;
+    } f;
+    struct {
+        double c, d;
+    } g;
+};
+
+struct FourDoublesInternal ReturnFourDoublesInternal(double a, double b, double c, double d) {
+    struct FourDoublesInternal e = { {a, b}, {c, d} };
+    return e;
+}
+
 struct FiveDoubles{
     double a, b, c, d, e;
 };