CODEWITHSUNDEEP
iphoneobjective-cstructios5automatic-ref-counting
Zsolt
Zsolt

Reputation: 3760

ARC forbids Objective-C objects in structs or unions despite marking the file -fno-objc-arc

ARC forbids Objective-C objects in structs or unions despite marking the file -fno-objc-arc? Why is this so?

I had the assumption that if you mark it -fno-objc-arc you don't have this restriction.

Upvotes: 85

Views: 53328

Answers (4)

Hiroshi Ichikawa
Hiroshi Ichikawa

Reputation: 636

Looks like this now works without errors, probably after this change.

i.e., You can put normal (strong) pointers to Objective-C objects in a C struct. It is managed by ARC e.g., it is unretained when the struct is destructed. Verified with:

$ clang --version Apple LLVM version 10.0.0 (clang-1000.11.45.2)

Upvotes: 8

János
János

Reputation: 35060

Rather than using a struct, you can create an Objective-C class to manage the data instead.

Upvotes: 30

zeiteisen
zeiteisen

Reputation: 7168

If you got this message try __unsafe_unretained. It is only safe, if the objects in the struct are unretained. Example: If you use OpenFeint with ARC the Class OFBragDelegateStrings says this error in a struct.

typedef struct OFBragDelegateStrings
{
     NSString* prepopulatedText;
     NSString* originalMessage;
} OFBragDelegateStrings;

to

typedef struct OFBragDelegateStrings
{
     __unsafe_unretained NSString* prepopulatedText;
     __unsafe_unretained NSString* originalMessage;
} OFBragDelegateStrings;

Upvotes: 169

voidStern
voidStern

Reputation: 3678

That is because arc can't track objects in structs or unions (since they are at that point plain C pointers).

Even though you marked the file/class in question with -fno-objc-arc you might still pass an object controlled by arc to it as parameter, which would most likely result in a memory leak.

Upvotes: 13

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