I've been testing some of our older libraries under GC, and have
found one coding pattern (that may well have been bad practice
anyway) that really does not work well under GC.
I used to use convenience constructors for NSMutableData objects as
a kind of lazy replacement for malloc.
That is, an assignment like this:
float *myPointer = [[NSMutableData dataWithLength:size*sizeof
(float)] mutableBytes]; // Memory freed at end of event loop
[...]
It seems like this (not surprisingly) doesn't work reliably under
GC, as the collector obviously has no way of knowing that you are
later looking at the memory originally addressed by myPointer. It
keeps track of objects and not pointers.
You kept a (default, no strong or weak modifier) pointer to data
inside the object, but no one kept a pointer to the object, so it was
collected.
As there are probably better ways of approaching this kind of
situation, I'd be interested in any suggestions or comments. The
way I was doing it before was probably just bad...
You can allocate GC'd memory with NSAllocateCollectable.
Jim
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