Index: src/atomic_builtins.h
==================================================================
--- src/atomic_builtins.h
+++ src/atomic_builtins.h
@@ -24,11 +24,11 @@
 of_atomic_int32_add(volatile int32_t *_Nonnull p, int32_t i)
 {
 	return __atomic_add_fetch(p, i, __ATOMIC_RELAXED);
 }
 
-static OF_INLINE void*
+static OF_INLINE void *_Nullable
 of_atomic_ptr_add(void *volatile _Nullable *_Nonnull p, intptr_t i)
 {
 	return __atomic_add_fetch(p, i, __ATOMIC_RELAXED);
 }
 
@@ -42,11 +42,11 @@
 of_atomic_int32_sub(volatile int32_t *_Nonnull p, int32_t i)
 {
 	return __atomic_sub_fetch(p, i, __ATOMIC_RELAXED);
 }
 
-static OF_INLINE void*
+static OF_INLINE void *_Nullable
 of_atomic_ptr_sub(void *volatile _Nullable *_Nonnull p, intptr_t i)
 {
 	return __atomic_sub_fetch(p, i, __ATOMIC_RELAXED);
 }
 

Index: src/atomic_no_threads.h
==================================================================
--- src/atomic_no_threads.h
+++ src/atomic_no_threads.h
@@ -24,11 +24,11 @@
 of_atomic_int32_add(volatile int32_t *_Nonnull p, int32_t i)
 {
 	return (*p += i);
 }
 
-static OF_INLINE void*
+static OF_INLINE void *_Nullable
 of_atomic_ptr_add(void *volatile _Nullable *_Nonnull p, intptr_t i)
 {
 	return (*(char* volatile*)p += i);
 }
 
@@ -42,11 +42,11 @@
 of_atomic_int32_sub(volatile int32_t *_Nonnull p, int32_t i)
 {
 	return (*p -= i);
 }
 
-static OF_INLINE void*
+static OF_INLINE void *_Nullable
 of_atomic_ptr_sub(void *volatile _Nullable *_Nonnull p, intptr_t i)
 {
 	return (*(char* volatile*)p -= i);
 }
 

Index: src/atomic_osatomic.h
==================================================================
--- src/atomic_osatomic.h
+++ src/atomic_osatomic.h
@@ -26,11 +26,11 @@
 of_atomic_int32_add(volatile int32_t *_Nonnull p, int32_t i)
 {
 	return OSAtomicAdd32(i, p);
 }
 
-static OF_INLINE void*
+static OF_INLINE void *_Nullable
 of_atomic_ptr_add(void *volatile _Nullable *_Nonnull p, intptr_t i)
 {
 #ifdef __LP64__
 	return (void*)OSAtomicAdd64(i, (int64_t*)p);
 #else
@@ -48,11 +48,11 @@
 of_atomic_int32_sub(volatile int32_t *_Nonnull p, int32_t i)
 {
 	return OSAtomicAdd32(-i, p);
 }
 
-static OF_INLINE void*
+static OF_INLINE void *_Nullable
 of_atomic_ptr_sub(void *volatile _Nullable *_Nonnull p, intptr_t i)
 {
 #ifdef __LP64__
 	return (void*)OSAtomicAdd64(-i, (int64_t*)p);
 #else

Index: src/atomic_powerpc.h
==================================================================
--- src/atomic_powerpc.h
+++ src/atomic_powerpc.h
@@ -44,11 +44,11 @@
 	);
 
 	return i;
 }
 
-static OF_INLINE void*
+static OF_INLINE void *_Nullable
 of_atomic_ptr_add(void *volatile _Nullable *_Nonnull p, intptr_t i)
 {
 	__asm__ __volatile__ (
 	    "0:\n\t"
 	    "lwarx	%0, 0, %2\n\t"
@@ -92,11 +92,11 @@
 	);
 
 	return i;
 }
 
-static OF_INLINE void*
+static OF_INLINE void *_Nullable
 of_atomic_ptr_sub(void *volatile _Nullable *_Nonnull p, intptr_t i)
 {
 	__asm__ __volatile__ (
 	    "0:\n\t"
 	    "lwarx	%0, 0, %2\n\t"

Index: src/atomic_sync_builtins.h
==================================================================
--- src/atomic_sync_builtins.h
+++ src/atomic_sync_builtins.h
@@ -24,11 +24,11 @@
 of_atomic_int32_add(volatile int32_t *_Nonnull p, int32_t i)
 {
 	return __sync_add_and_fetch(p, i);
 }
 
-static OF_INLINE void*
+static OF_INLINE void *_Nullable
 of_atomic_ptr_add(void *volatile _Nullable *_Nonnull p, intptr_t i)
 {
 	return __sync_add_and_fetch(p, (void*)i);
 }
 
@@ -42,11 +42,11 @@
 of_atomic_int32_sub(volatile int32_t *_Nonnull p, int32_t i)
 {
 	return __sync_sub_and_fetch(p, i);
 }
 
-static OF_INLINE void*
+static OF_INLINE void *_Nullable
 of_atomic_ptr_sub(void *volatile _Nullable *_Nonnull p, intptr_t i)
 {
 	return __sync_sub_and_fetch(p, (void*)i);
 }
 

Index: src/atomic_x86.h
==================================================================
--- src/atomic_x86.h
+++ src/atomic_x86.h
@@ -55,11 +55,11 @@
 	);
 
 	return i;
 }
 
-static OF_INLINE void*
+static OF_INLINE void *_Nullable
 of_atomic_ptr_add(void *volatile _Nullable *_Nonnull p, intptr_t i)
 {
 #if defined(OF_X86_64_ASM)
 	__asm__ __volatile__ (
 	    "lock\n\t"
@@ -125,11 +125,11 @@
 	);
 
 	return i;
 }
 
-static OF_INLINE void*
+static OF_INLINE void *_Nullable
 of_atomic_ptr_sub(void *volatile _Nullable *_Nonnull p, intptr_t i)
 {
 #if defined(OF_X86_64_ASM)
 	__asm__ __volatile__ (
 	    "negq	%0\n\t"