Tagged pointer format changes in iOS 14 break JSONKit on ARM64

[Dir9119]

Hello,

As described here, Apple decided to change tagged pointers format in iOS 14 on ARM64. This causes JSONKit's jk_object_class function to determine object classes incorrectly and makes JSONKit virtually unusable.

[asgeo1]

I'm having this issue too. Is there any workaround?

[adancondori]

I'm having this issue too. Exist any alternative for this error.?

[garyZJ]

I'm having this issue too.

[Kirow]

If you using code from #158 you can replace (straight forward solution)

return(((uintptr_t)objectPtr) >> 60);

with

if (@available(iOS 14, *)) {
   return(((uintptr_t)objectPtr) & 0x7);
} else {
   return(((uintptr_t)objectPtr) >> 60);
}

if you using code from master branch you will need to update isa usage

patch.diff

diff --git a/JSONKit.m b/JSONKit.m
index 0e9331f..c47ab02 100644
--- a/JSONKit.m
+++ b/JSONKit.m
@@ -677,7 +677,7 @@ static JKArray *_JKArrayCreate(id *objects, NSUInteger count, BOOL mutableCollec
   NSCParameterAssert((objects != NULL) && (_JKArrayClass != NULL) && (_JKArrayInstanceSize > 0UL));
   JKArray *array = NULL;
   if(JK_EXPECT_T((array = (JKArray *)calloc(1UL, _JKArrayInstanceSize)) != NULL)) { // Directly allocate the JKArray instance via calloc.
-    array->isa      = _JKArrayClass;
+    object_setClass(array, _JKArrayClass);
     if((array = [array init]) == NULL) { return(NULL); }
     array->capacity = count;
     array->count    = count;
@@ -928,7 +928,7 @@ static JKDictionary *_JKDictionaryCreate(id *keys, NSUInteger *keyHashes, id *ob
   NSCParameterAssert((keys != NULL) && (keyHashes != NULL) && (objects != NULL) && (_JKDictionaryClass != NULL) && (_JKDictionaryInstanceSize > 0UL));
   JKDictionary *dictionary = NULL;
   if(JK_EXPECT_T((dictionary = (JKDictionary *)calloc(1UL, _JKDictionaryInstanceSize)) != NULL)) { // Directly allocate the JKDictionary instance via calloc.
-    dictionary->isa      = _JKDictionaryClass;
+    object_setClass(dictionary, _JKDictionaryClass);
     if((dictionary = [dictionary init]) == NULL) { return(NULL); }
     dictionary->capacity = _JKDictionaryCapacityForCount(count);
     dictionary->count    = 0UL;
@@ -2596,7 +2596,7 @@ static int jk_encode_add_atom_to_buffer(JKEncodeState *encodeState, void *object
 
 
   BOOL   workAroundMacOSXABIBreakingBug = (JK_EXPECT_F(((NSUInteger)object) & 0x1))     ? YES  : NO;
-  void  *objectISA                      = (JK_EXPECT_F(workAroundMacOSXABIBreakingBug)) ? NULL : *((void **)objectPtr);
+  void  *objectISA                      = (JK_EXPECT_F(workAroundMacOSXABIBreakingBug)) ? NULL : ((void *)object_getClass(objectPtr));
   if(JK_EXPECT_F(workAroundMacOSXABIBreakingBug)) { goto slowClassLookup; }
 
        if(JK_EXPECT_T(objectISA == encodeState->fastClassLookup.stringClass))     { isClass = JKClassString;     }
@@ -2792,7 +2792,7 @@ static int jk_encode_add_atom_to_buffer(JKEncodeState *encodeState, void *object
           for(id keyObject in enumerateObject) {
             if(JK_EXPECT_T(printComma)) { if(JK_EXPECT_F(jk_encode_write1(encodeState, 0L, ","))) { return(1); } }
             printComma = 1;
-            void *keyObjectISA = *((void **)keyObject);
+            void *keyObjectISA = (void *)object_getClass(keyObject);
             if(JK_EXPECT_F((keyObjectISA != encodeState->fastClassLookup.stringClass)) && JK_EXPECT_F(([keyObject isKindOfClass:[NSString class]] == NO))) { jk_encode_error(encodeState, @"Key must be a string object."); return(1); }
             if(JK_EXPECT_F(jk_encode_add_atom_to_buffer(encodeState, keyObject)))                                                        { return(1); }
             if(JK_EXPECT_F(jk_encode_write1(encodeState, 0L, ":")))                                                                      { return(1); }
@@ -2804,7 +2804,7 @@ static int jk_encode_add_atom_to_buffer(JKEncodeState *encodeState, void *object
           for(idx = 0L; idx < dictionaryCount; idx++) {
             if(JK_EXPECT_T(printComma)) { if(JK_EXPECT_F(jk_encode_write1(encodeState, 0L, ","))) { return(1); } }
             printComma = 1;
-            void *keyObjectISA = *((void **)keys[idx]);
+            void *keyObjectISA = (void *)object_getClass(keys[idx]);
             if(JK_EXPECT_F(keyObjectISA != encodeState->fastClassLookup.stringClass) && JK_EXPECT_F([(id)keys[idx] isKindOfClass:[NSString class]] == NO)) { jk_encode_error(encodeState, @"Key must be a string object."); return(1); }
             if(JK_EXPECT_F(jk_encode_add_atom_to_buffer(encodeState, keys[idx])))    { return(1); }
             if(JK_EXPECT_F(jk_encode_write1(encodeState, 0L, ":")))                  { return(1); }

however there was comment not to use object_getClass due to performance impact, but goal was to fix the crashes.

P.S. Did not test this deeply, but seems to be working...

[miyiyake]

NSNumber 类型数据都有问题，换成NSString类型就没有问题

[codedeman]

If you using code from #158 you can replace (straight forward solution)

return(((uintptr_t)objectPtr) >> 60);

with

if (@available(iOS 14, *)) {
   return(((uintptr_t)objectPtr) & 0x7);
} else {
   return(((uintptr_t)objectPtr) >> 60);
}

if you using code from master branch you will need to update isa usage

patch.diff
however there was comment not to use object_getClass due to performance impact, but goal was to fix the crashes.

P.S. Did not test this deeply, but seems to be working...

it's work for me

[jcbertin]

I have fixed #158 for new format of tagged pointers in macOS on Apple Silicon and last versions of iOS, watchOS and tvOS. Also replaced isa dereference by fast class lookup.

Please comment if it is not working for you…

[jcbertin]

For people curious to compare #158 and NSJSON, see JSONKitTest.