A non-functional `.m` file that contains all the features that are absent from MulleObjC.
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Bad Code

These are examples of Objective-C 2.0 code, that will not work with MulleObjC.


MulleObjC has no support for modules and the @import directive. This will give a compiler error:

@import Whatever;             // @import doesn't work

See Porting @import for code conversion tips.

Unsupported @property attributes

The attributes atomic,weak,strong,nullable,unsafe_retained class are all unknown to MulleObjC and will produce errors:

@interface Foo

// unsupported property attribute
@property( atomic) id  a;
@property( weak) id  b;
@property( strong) id  c;
@property( nullable) id  d;      // nullable can be #defined away without trouble
@property( unsafe_unretained) e; // shpuld be no different to assign though
@property( class) id  f;         // class has a chance of being supported sometime

See Porting @property for conversion tips.

@synthesize with different ivar name

You can not synthesize to a different name, ivar must be '_'<name>:

// continuing the interface declaration...
// we need the next two declarations for @synthesize to complain
@property( assign) id g;
@property( assign) id h;


@implementation Foo

@synthesize g = _g1;

// specfiying a property as dynamic with @dynamic does nothing in MulleObjC
@dynamic h;

See Porting @synthesize for code conversion tips.


Subscripting for NSArray and NSDictionary or any other class is not supported. Instead the compiler will use C indexing:

// subscripting is not supported
- (id) getFirst:(NSArray *) array
   return( array[ 0]);

See Porting Subscripting for code conversion tips.


ARC code will crash or leak depending on what you are doing:

- (id) ARC
   return( [[NSArray alloc] init]);

See Porting ARC code for code conversion tips.

Dot syntax

There is no operator overloading ‘.’ in MulleObjC. ‘.’ is used to accessed struct and union fields, not objects:

// dotsyntax is not supported
- (void) dotsyntax
   self.h = @"x";

See Porting Dot Syntax for code conversion tips.


// generics are not supported
- (void) generics:(NSArray<NSString *> *) array

See Porting Generics for code conversion tips.


// blocks are not supported
- (void) blocks:(int (^)(NSString *)) aBlock

See Porting Blocks for code conversion tips.


// synchronized is not supported
- (void) synchronized
   @synchronized( self)

See Porting @synchronized for code conversion tips.

@YES …

@YES and @NO are not supported, use @(YES),@(NO) or +numberWithBool: instead

// literal BOOL is not supported
- (NSNumber *) literalBOOL
   return( @YES);

Note there is a good chance that the mulle-clang compiler will forbid the use of non-numeric constants for boxing. So for example @INT_MAX may work currently but it may not in the future.

Protocol *

Protocol * as such doesn’t exist in MulleObjC. Use PROTOCOL instead:

// Protocol * is not supported, use PROTOCOL
- (void) keepProtocol:(Protocol *) proto
   [proto retain];  // PROTOCOL is not an object

See Porting Protocol for code conversion tips.

Casting SEL to (char *)

In the Apple runtime a SEL is basically a string, but this is not true in MulleObjC:

- (void) printSelectorAsCString:(SEL) sel
   printf( "%s\n", sel); // SEL is not a C-String in MulleObjC

Accessing variable arguments with va_list

Variable arguments are NOT va_list in MulleObjC, but mulle-vararg instead:

- (void) variableArguments:(NSString *) format, ...
   va_list   args;

   va_start( args, format);
   va_end( args);


See Porting Varargs for code conversion tips.


@package is an unsupported keyword.It will produce a compiler error:

@interface NoWorky

See Porting Protocol for code conversion tips.

See the output for yourself

Download (bad-code.m) and let the compiler tell you all about it.


Differences will list succinctly the differences between MulleObjC and Objective-C 2.0.