Question

When I return a CFDataRef by

(CFDataRef)MyFunction{
    .....
    CFDataRef data = CFDataCreate(NULL, buf, bufLen);
    free(buf);
    return data;
}

There is a memory leak, how to make CFDataRef autorelease?
the method [data autorelease] doesn’t exit.

Answer 1

You can’t autorelease Core Foundation objects. (However, you can autorelease Core Foundation objects that support toll-free bridging such as CFDataRef; see @newacct’s answer below.)

The Objective-C convention is to name your method such that it starts with the word new to indicate that the caller is responsible for releasing its return value. For example:

+ (CFDataRef)newDataRef {
    return CFDataCreate(...);
}

CFDataRef myDataRef = [self newDataRef];
...
CFRelease(myDataRef);

If you conform to this naming convention, the Xcode static analyzer will correctly flag Core Foundation memory managment issues.