On Jun 6, 2008, at 16:42, Bill Bumgarner wrote:

The easiest way to do this is to simply to use data once after the for() loop:

        NSData* data = <get it from somewhere>;
        const unsigned char* bytes = [data bytes];
        NSUInteger count = [data length];
        for (NSUInteger i = 0; i < count; i++)
                something = bytes [i];
        [data self];

Yup. I don't particularly like it either. Fortunately, it is an uncommon case -- most of the objects in the AppKit/Foundation "just work". This kind of a problem arises when something leverages the C in Objective-C.

Thanks, and to Shawn for the same suggestion. It's a pragmatic solution I can deal with.

A little inner voice insists on asking, though, how we know some future version of the compiler might not optimize '[data self]' upwards before the loop, if it decides that nothing inside the loop references anything non-local:

        NSData* data = <get it from somewhere>;
        const unsigned char* bytes = [data bytes];
        NSUInteger count = [data length];
        NSUInteger largestByte = 0;
        for (NSUInteger i = 0; i < count; i++)
                largestByte = MAX (largestByte , bytes [i]);
        [data self];

TBH, I don't see any real solution without making the compiler aware of the GC consequences of its optimizations.


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