Silences some warnings that newer versions of the compiler(s) complain about.

1. Some of the string format argument specifiers used `%lu` to display `NSUInteger` values.

`%lu` specifies a type of `unsigned long`, and `NSUInteger` maps to either `unsigned int` or `unsigned long`, depending on whether or not you're targeting a 32-bit or 64-bit ABI, respectively.

On a 32-bit architecture (at least for the architectures / compilers that JSONKit will be used on), `unsigned long` and `unsigned int` just so happen to use the same primitive type- a 4 byte 32-bit value.

On a 64-bit architecture (again, for the architectures / compilers that JSONKit will be used on), `unsigned int` stays the same at 4 bytes, however `unsigned long` grows to 64-bits / 8 bytes.

The long and the short of it is this that using `%lu` allows you to easily support 32-bit and 64-bits with out a lot of effort.

However, technically, the C standard says that `int` and `long` are strictly different ranks, and it's generally considered poor form to take advantage of platform specific details in this case.

The proper fix is to add explicit type casts to `unsigned long`.  This makes the implied behavior explicit, and eliminates the warnings from newer versions of the compiler.

FYI, `gcc` did this for a long time and seems to be something that is either new or enabled by default in `clang` / `Xcode`.

Other good warning flags you should consider enabling by default (from Xcode 4.3):

Implicit Conversion to 32 Bit Type
Suspicious Implicit Conversions
Hidden Local Variables

2. Newer compiler warns about deprecated `id` `isa` usage.

I found jwz's commentary about breaking API's pretty funny: http://www.jwz.org/blog/2012/06/i-have-ported-xscreensaver-to-the-iphone/

Author: johnezang

JSONKit.m

@@ -742,14 +742,14 @@ - (NSUInteger)count
 - (void)getObjects:(id *)objectsPtr range:(NSRange)range
 {
   NSParameterAssert((objects != NULL) && (count <= capacity));
-  if((objectsPtr     == NULL)  && (NSMaxRange(range) > 0UL))   { [NSException raise:NSRangeException format:@"*** -[%@ %@]: pointer to objects array is NULL but range length is %lu", NSStringFromClass([self class]), NSStringFromSelector(_cmd), NSMaxRange(range)];        }
-  if((range.location >  count) || (NSMaxRange(range) > count)) { [NSException raise:NSRangeException format:@"*** -[%@ %@]: index (%lu) beyond bounds (%lu)",                          NSStringFromClass([self class]), NSStringFromSelector(_cmd), NSMaxRange(range), count]; }
+  if((objectsPtr     == NULL)  && (NSMaxRange(range) > 0UL))   { [NSException raise:NSRangeException format:@"*** -[%@ %@]: pointer to objects array is NULL but range length is %lu", NSStringFromClass([self class]), NSStringFromSelector(_cmd), (unsigned long)NSMaxRange(range)];        }
+  if((range.location >  count) || (NSMaxRange(range) > count)) { [NSException raise:NSRangeException format:@"*** -[%@ %@]: index (%lu) beyond bounds (%lu)",                          NSStringFromClass([self class]), NSStringFromSelector(_cmd), (unsigned long)NSMaxRange(range), (unsigned long)count]; }
   memcpy(objectsPtr, objects + range.location, range.length * sizeof(id));
 }
 
 - (id)objectAtIndex:(NSUInteger)objectIndex
 {
-  if(objectIndex >= count) { [NSException raise:NSRangeException format:@"*** -[%@ %@]: index (%lu) beyond bounds (%lu)", NSStringFromClass([self class]), NSStringFromSelector(_cmd), objectIndex, count]; }
+  if(objectIndex >= count) { [NSException raise:NSRangeException format:@"*** -[%@ %@]: index (%lu) beyond bounds (%lu)", NSStringFromClass([self class]), NSStringFromSelector(_cmd), (unsigned long)objectIndex, (unsigned long)count]; }
   NSParameterAssert((objects != NULL) && (count <= capacity) && (objects[objectIndex] != NULL));
   return(objects[objectIndex]);
 }
@@ -770,7 +770,7 @@ - (void)insertObject:(id)anObject atIndex:(NSUInteger)objectIndex
 {
   if(mutations   == 0UL)   { [NSException raise:NSInternalInconsistencyException format:@"*** -[%@ %@]: mutating method sent to immutable object", NSStringFromClass([self class]), NSStringFromSelector(_cmd)]; }
   if(anObject    == NULL)  { [NSException raise:NSInvalidArgumentException       format:@"*** -[%@ %@]: attempt to insert nil",                    NSStringFromClass([self class]), NSStringFromSelector(_cmd)]; }
-  if(objectIndex >  count) { [NSException raise:NSRangeException                 format:@"*** -[%@ %@]: index (%lu) beyond bounds (%lu)",          NSStringFromClass([self class]), NSStringFromSelector(_cmd), objectIndex, count + 1UL]; }
+  if(objectIndex >  count) { [NSException raise:NSRangeException                 format:@"*** -[%@ %@]: index (%lu) beyond bounds (%lu)",          NSStringFromClass([self class]), NSStringFromSelector(_cmd), (unsigned long)objectIndex, (unsigned long)(count + 1UL)]; }
 #ifdef __clang_analyzer__
   [anObject retain]; // Stupid clang analyzer...  Issue #19.
 #else
@@ -783,7 +783,7 @@ - (void)insertObject:(id)anObject atIndex:(NSUInteger)objectIndex
 - (void)removeObjectAtIndex:(NSUInteger)objectIndex
 {
   if(mutations   == 0UL)   { [NSException raise:NSInternalInconsistencyException format:@"*** -[%@ %@]: mutating method sent to immutable object", NSStringFromClass([self class]), NSStringFromSelector(_cmd)]; }
-  if(objectIndex >= count) { [NSException raise:NSRangeException                 format:@"*** -[%@ %@]: index (%lu) beyond bounds (%lu)",          NSStringFromClass([self class]), NSStringFromSelector(_cmd), objectIndex, count]; }
+  if(objectIndex >= count) { [NSException raise:NSRangeException                 format:@"*** -[%@ %@]: index (%lu) beyond bounds (%lu)",          NSStringFromClass([self class]), NSStringFromSelector(_cmd), (unsigned long)objectIndex, (unsigned long)count]; }
   _JKArrayRemoveObjectAtIndex(self, objectIndex);
   mutations = (mutations == NSUIntegerMax) ? 1UL : mutations + 1UL;
 }
@@ -792,7 +792,7 @@ - (void)replaceObjectAtIndex:(NSUInteger)objectIndex withObject:(id)anObject
 {
   if(mutations   == 0UL)   { [NSException raise:NSInternalInconsistencyException format:@"*** -[%@ %@]: mutating method sent to immutable object", NSStringFromClass([self class]), NSStringFromSelector(_cmd)]; }
   if(anObject    == NULL)  { [NSException raise:NSInvalidArgumentException       format:@"*** -[%@ %@]: attempt to insert nil",                    NSStringFromClass([self class]), NSStringFromSelector(_cmd)]; }
-  if(objectIndex >= count) { [NSException raise:NSRangeException                 format:@"*** -[%@ %@]: index (%lu) beyond bounds (%lu)",          NSStringFromClass([self class]), NSStringFromSelector(_cmd), objectIndex, count]; }
+  if(objectIndex >= count) { [NSException raise:NSRangeException                 format:@"*** -[%@ %@]: index (%lu) beyond bounds (%lu)",          NSStringFromClass([self class]), NSStringFromSelector(_cmd), (unsigned long)objectIndex, (unsigned long)count]; }
 #ifdef __clang_analyzer__
   [anObject retain]; // Stupid clang analyzer...  Issue #19.
 #else
@@ -896,7 +896,7 @@ + (id)allocWithZone:(NSZone *)zone
 };
 
 static NSUInteger _JKDictionaryCapacityForCount(NSUInteger count) {
-  NSUInteger bottom = 0UL, top = sizeof(jk_dictionaryCapacities) / sizeof(NSUInteger), mid = 0UL, tableSize = lround(floor((count) * 1.33));
+  NSUInteger bottom = 0UL, top = sizeof(jk_dictionaryCapacities) / sizeof(NSUInteger), mid = 0UL, tableSize = (NSUInteger)lround(floor(((double)count) * 1.33));
   while(top > bottom) { mid = (top + bottom) / 2UL; if(jk_dictionaryCapacities[mid] < tableSize) { bottom = mid + 1UL; } else { top = mid; } }
   return(jk_dictionaryCapacities[bottom]);
 }
@@ -2592,21 +2592,23 @@ static int jk_encode_add_atom_to_buffer(JKEncodeState *encodeState, void *object
   //     
   // XXX XXX XXX XXX
 
-  BOOL workAroundMacOSXABIBreakingBug = NO;
-  if(JK_EXPECT_F(((NSUInteger)object) & 0x1)) { workAroundMacOSXABIBreakingBug = YES; goto slowClassLookup; }
 
-       if(JK_EXPECT_T(object->isa == encodeState->fastClassLookup.stringClass))     { isClass = JKClassString;     }
-  else if(JK_EXPECT_T(object->isa == encodeState->fastClassLookup.numberClass))     { isClass = JKClassNumber;     }
-  else if(JK_EXPECT_T(object->isa == encodeState->fastClassLookup.dictionaryClass)) { isClass = JKClassDictionary; }
-  else if(JK_EXPECT_T(object->isa == encodeState->fastClassLookup.arrayClass))      { isClass = JKClassArray;      }
-  else if(JK_EXPECT_T(object->isa == encodeState->fastClassLookup.nullClass))       { isClass = JKClassNull;       }
+  BOOL   workAroundMacOSXABIBreakingBug = (JK_EXPECT_F(((NSUInteger)object) & 0x1))     ? YES  : NO;
+  void  *objectISA                      = (JK_EXPECT_F(workAroundMacOSXABIBreakingBug)) ? NULL : *((void **)objectPtr);
+  if(JK_EXPECT_F(workAroundMacOSXABIBreakingBug)) { goto slowClassLookup; }
+
+       if(JK_EXPECT_T(objectISA == encodeState->fastClassLookup.stringClass))     { isClass = JKClassString;     }
+  else if(JK_EXPECT_T(objectISA == encodeState->fastClassLookup.numberClass))     { isClass = JKClassNumber;     }
+  else if(JK_EXPECT_T(objectISA == encodeState->fastClassLookup.dictionaryClass)) { isClass = JKClassDictionary; }
+  else if(JK_EXPECT_T(objectISA == encodeState->fastClassLookup.arrayClass))      { isClass = JKClassArray;      }
+  else if(JK_EXPECT_T(objectISA == encodeState->fastClassLookup.nullClass))       { isClass = JKClassNull;       }
   else {
   slowClassLookup:
-         if(JK_EXPECT_T([object isKindOfClass:[NSString     class]])) { if(workAroundMacOSXABIBreakingBug == NO) { encodeState->fastClassLookup.stringClass     = object->isa; } isClass = JKClassString;     }
-    else if(JK_EXPECT_T([object isKindOfClass:[NSNumber     class]])) { if(workAroundMacOSXABIBreakingBug == NO) { encodeState->fastClassLookup.numberClass     = object->isa; } isClass = JKClassNumber;     }
-    else if(JK_EXPECT_T([object isKindOfClass:[NSDictionary class]])) { if(workAroundMacOSXABIBreakingBug == NO) { encodeState->fastClassLookup.dictionaryClass = object->isa; } isClass = JKClassDictionary; }
-    else if(JK_EXPECT_T([object isKindOfClass:[NSArray      class]])) { if(workAroundMacOSXABIBreakingBug == NO) { encodeState->fastClassLookup.arrayClass      = object->isa; } isClass = JKClassArray;      }
-    else if(JK_EXPECT_T([object isKindOfClass:[NSNull       class]])) { if(workAroundMacOSXABIBreakingBug == NO) { encodeState->fastClassLookup.nullClass       = object->isa; } isClass = JKClassNull;       }
+         if(JK_EXPECT_T([object isKindOfClass:[NSString     class]])) { if(workAroundMacOSXABIBreakingBug == NO) { encodeState->fastClassLookup.stringClass     = objectISA; } isClass = JKClassString;     }
+    else if(JK_EXPECT_T([object isKindOfClass:[NSNumber     class]])) { if(workAroundMacOSXABIBreakingBug == NO) { encodeState->fastClassLookup.numberClass     = objectISA; } isClass = JKClassNumber;     }
+    else if(JK_EXPECT_T([object isKindOfClass:[NSDictionary class]])) { if(workAroundMacOSXABIBreakingBug == NO) { encodeState->fastClassLookup.dictionaryClass = objectISA; } isClass = JKClassDictionary; }
+    else if(JK_EXPECT_T([object isKindOfClass:[NSArray      class]])) { if(workAroundMacOSXABIBreakingBug == NO) { encodeState->fastClassLookup.arrayClass      = objectISA; } isClass = JKClassArray;      }
+    else if(JK_EXPECT_T([object isKindOfClass:[NSNull       class]])) { if(workAroundMacOSXABIBreakingBug == NO) { encodeState->fastClassLookup.nullClass       = objectISA; } isClass = JKClassNull;       }
     else {
       if((rerunningAfterClassFormatter == NO) && (
 #ifdef __BLOCKS__
@@ -2788,7 +2790,8 @@ 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;
-            if(JK_EXPECT_F((keyObject->isa      != encodeState->fastClassLookup.stringClass)) && JK_EXPECT_F(([keyObject   isKindOfClass:[NSString class]] == NO))) { jk_encode_error(encodeState, @"Key must be a string object."); return(1); }
+            void *keyObjectISA = *((void **)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); }
             if(JK_EXPECT_F(jk_encode_add_atom_to_buffer(encodeState, (void *)CFDictionaryGetValue((CFDictionaryRef)object, keyObject)))) { return(1); }
@@ -2799,7 +2802,8 @@ 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;
-            if(JK_EXPECT_F(((id)keys[idx])->isa != 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); }
+            void *keyObjectISA = *((void **)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); }
             if(JK_EXPECT_F(jk_encode_add_atom_to_buffer(encodeState, objects[idx]))) { return(1); }