Fixed jump address calculation

src/build/asm/Finalize.go

@@ -57,23 +57,25 @@ func (a Assembler) Finalize() ([]byte, []byte) {
 			code = x64.Call(code, 0x00_00_00_00)
 			size := 4
 			label := x.Data.(*Label)
-			nextInstructionAddress := Address(len(code))
 
-			pointers = append(pointers, &Pointer{
+			pointer := &Pointer{
 				Position: Address(len(code) - size),
 				OpSize:   1,
 				Size:     uint8(size),
-				Resolve: func() Address {
-					destination, exists := labels[label.Name]
+			}
 
-					if !exists {
-						panic("unknown call label")
-					}
+			pointer.Resolve = func() Address {
+				destination, exists := labels[label.Name]
 
-					distance := destination - nextInstructionAddress
-					return Address(distance)
-				},
-			})
+				if !exists {
+					panic("unknown jump label")
+				}
+
+				distance := destination - (pointer.Position + Address(pointer.Size))
+				return Address(distance)
+			}
+
+			pointers = append(pointers, pointer)
 
 		case COMMENT:
 			continue
@@ -106,23 +108,25 @@ func (a Assembler) Finalize() ([]byte, []byte) {
 
 			size := 1
 			label := x.Data.(*Label)
-			nextInstructionAddress := Address(len(code))
 
-			pointers = append(pointers, &Pointer{
+			pointer := &Pointer{
 				Position: Address(len(code) - size),
 				OpSize:   1,
 				Size:     uint8(size),
-				Resolve: func() Address {
-					destination, exists := labels[label.Name]
+			}
 
-					if !exists {
-						panic("unknown jump label")
-					}
+			pointer.Resolve = func() Address {
+				destination, exists := labels[label.Name]
 
-					distance := destination - nextInstructionAddress
-					return Address(distance)
-				},
-			})
+				if !exists {
+					panic("unknown jump label")
+				}
+
+				distance := destination - (pointer.Position + Address(pointer.Size))
+				return Address(distance)
+			}
+
+			pointers = append(pointers, pointer)
 
 		case LABEL:
 			labels[x.Data.(*Label).Name] = Address(len(code))
@@ -269,8 +273,16 @@ restart:
 				following.Position += offset
 			}
 
-			code = append(left, jump...)
-			code = append(code, right...)
+			for key, address := range labels {
+				if address > pointer.Position {
+					labels[key] += offset
+				}
+			}
+
+			code = make([]byte, len(left)+len(jump)+len(right))
+			copy(code, left)
+			copy(code[len(left):], jump)
+			copy(code[len(left)+len(jump):], right)
 			goto restart
 		}