Index: src/invocation/apple-call-x86_64.S
==================================================================
--- src/invocation/apple-call-x86_64.S
+++ src/invocation/apple-call-x86_64.S
@@ -15,10 +15,12 @@
  * file.
  */
 
 #include "config.h"
 
+#include "invoke-x86_64.h"
+
 .globl _of_invocation_call
 
 .section __TEXT, __text, regular, pure_instructions
 _of_invocation_call:
 	pushq	%rbp
@@ -63,17 +65,17 @@
 	movq	8(%rdi), %rsi
 
 	movb	225(%rdi), %r11b
 	movq	0(%rdi), %rdi
 
-	cmpb	$1, %r11b
+	cmpb	$RETURN_TYPE_STRET, %r11b
 	je	Lcall_send_stret
 
-	cmpb	$4, %r11b
+	cmpb	$RETURN_TYPE_JMP, %r11b
 	je	_objc_msgSend
 
-	cmpb	$5, %r11b
+	cmpb	$RETURN_TYPE_JMP_STRET, %r11b
 	je	_objc_msgSend_stret
 
 	call	_objc_msgSend
 
 Lafter_send:
@@ -83,14 +85,14 @@
 	movdqa	%xmm0, 64(%rdi)
 	movdqa	%xmm1, 80(%rdi)
 
 	movb	225(%rdi), %r11b
 
-	cmpb	$2, %r11b
+	cmpb	$RETURN_TYPE_X87, %r11b
 	je	Lpop_long_double
 
-	cmpb	$3, %r11b
+	cmpb	$RETURN_TYPE_COMPLEX_X87, %r11b
 	je	Lpop_complex_long_double
 
 Lreturn:
 	movq	%rbp, %rsp
 	popq	%rbp

Index: src/invocation/call-x86_64-elf.S
==================================================================
--- src/invocation/call-x86_64-elf.S
+++ src/invocation/call-x86_64-elf.S
@@ -15,10 +15,12 @@
  * file.
  */
 
 #include "config.h"
 
+#include "invoke-x86_64.h"
+
 .globl of_invocation_call
 
 .section .text
 of_invocation_call:
 	pushq	%rbp
@@ -27,13 +29,13 @@
 	subq	$16, %rsp
 	andq	$-16, %rsp
 	movq	%rdi, -8(%rbp)
 
 	movb	225(%rdi), %r11b
-	cmpb	$1, %r11b
+	cmpb	$RETURN_TYPE_STRET, %r11b
 	je	.lookup_stret
-	cmpb	$4, %r11b
+	cmpb	$RETURN_TYPE_JMP_STRET, %r11b
 	je	.lookup_stret
 
 	movq	8(%rdi), %rsi
 	movq	0(%rdi), %rdi
 	call	objc_msg_lookup@PLT
@@ -77,13 +79,13 @@
 	movq	8(%rdi), %rsi
 
 	movb	225(%rdi), %r11b
 	movq	0(%rdi), %rdi
 
-	cmpb	$4, %r11b
+	cmpb	$RETURN_TYPE_JMP, %r11b
 	je	.jmp_into_method
-	cmpb	$5, %r11b
+	cmpb	$RETURN_TYPE_JMP_STRET, %r11b
 	je	.jmp_into_method
 
 	movq	-16(%rbp), %r11
 	call	*%r11
 
@@ -94,14 +96,14 @@
 	movdqa	%xmm0, 64(%rdi)
 	movdqa	%xmm1, 80(%rdi)
 
 	movb	225(%rdi), %r11b
 
-	cmpb	$2, %r11b
+	cmpb	$RETURN_TYPE_X87, %r11b
 	je	.pop_long_double
 
-	cmpb	$3, %r11b
+	cmpb	$RETURN_TYPE_COMPLEX_X87, %r11b
 	je	.pop_complex_long_double
 
 .return:
 	movq	%rbp, %rsp
 	popq	%rbp

ADDED   src/invocation/invoke-x86_64.h
Index: src/invocation/invoke-x86_64.h
==================================================================
--- /dev/null
+++ src/invocation/invoke-x86_64.h
@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017,
+ *               2018
+ *   Jonathan Schleifer <js@heap.zone>
+ *
+ * All rights reserved.
+ *
+ * This file is part of ObjFW. It may be distributed under the terms of the
+ * Q Public License 1.0, which can be found in the file LICENSE.QPL included in
+ * the packaging of this file.
+ *
+ * Alternatively, it may be distributed under the terms of the GNU General
+ * Public License, either version 2 or 3, which can be found in the file
+ * LICENSE.GPLv2 or LICENSE.GPLv3 respectively included in the packaging of this
+ * file.
+ */
+
+#define RETURN_TYPE_NORMAL	0
+#define RETURN_TYPE_STRET	1
+#define RETURN_TYPE_X87		2
+#define RETURN_TYPE_COMPLEX_X87	3
+#define RETURN_TYPE_JMP		4
+#define RETURN_TYPE_JMP_STRET	5

Index: src/invocation/invoke-x86_64.m
==================================================================
--- src/invocation/invoke-x86_64.m
+++ src/invocation/invoke-x86_64.m
@@ -25,26 +25,19 @@
 #import "OFMethodSignature.h"
 
 #import "OFInvalidFormatException.h"
 #import "OFOutOfMemoryException.h"
 
+#import "invoke-x86_64.h"
+
 #import "macros.h"
 
 #define NUM_GPR_IN 6
 #define NUM_GPR_OUT 2
 #define NUM_SSE_IN 8
 #define NUM_X87_OUT 2
 
-enum {
-	RETURN_TYPE_NORMAL,
-	RETURN_TYPE_STRUCT,
-	RETURN_TYPE_X87,
-	RETURN_TYPE_COMPLEX_X87,
-	RETURN_TYPE_JMP,
-	RETURN_TYPE_JMP_STRET
-};
-
 struct call_context {
 	uint64_t GPR[NUM_GPR_IN + NUM_GPR_OUT];
 	__m128 SSE[NUM_SSE_IN];
 	long double X87[NUM_X87_OUT];
 	uint8_t numSSEUsed;