On Dec 6, 2011, at 2:47 PM, Larry Campbell wrote:
> void allocAndRaise()
> {
> [[[NSString alloc] initWithString:@"foo bar and zot"] autorelease];
> [NSException raise:@"foo" format:@"bar"];
> }
>
> //#define LEAK
>
> void foo()
> {
> NSAutoreleasePool *pool = [NSAutoreleasePool new];
> NS_DURING {
> allocAndRaise();
> } NS_HANDLER {
> #ifdef LEAK
> [localException raise];
> #else
> [localException retain]; // I don't think this workaround should
> be necessary, but it is
> [pool release];
> [[localException autorelease] raise];
> #endif
> } NS_ENDHANDLER
> [pool release];
> }
The workaround is necessary because the exception object raised in
allocAndRaise() has been autoreleased. It is no longer owned by anything and
is only still around because the pool containing the pending release(s) has not
been drained. When you drain it, that executes the pending release(s) and
ultimately deallocates it.
That is one of the reasons you are discouraged from releasing/draining
autorelease pools in exception handlers or @finally blocks.
As Greg Parker said, the "#ifdef LEAK" code is preferred and will not leak the
objects that have been autoreleased.
Regards,
Ken
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