On 29 Apr 2008, at 07:39, Graham J Lee wrote:
Hi Gregory,
On 28 Apr 2008, at 22:52, Gregory John Casamento wrote:
Damn... yes, I was thinking of TEST_RELEASE.
[...]
Gregory John Casamento wrote:
RELEASE is a #define which does the standard checking that needs to
be done when doing a release.
In what way needs to be done? The scenarios for sending [obj
release] are:
1. obj is nil; nothing happens.
2. obj is not an id; crash (if you're lucky).
3. obj is an id which does not respond to @selector(release), and
has no forwarding mechanism; runtime exception.
4. obj is an id which responds to @selector(release) or consumes it
in some other way; it does its stuff.
Case 1 is a special example of case 4, so case 2 needs to be tested
for and some might argue case 3. But the macro is defined as:
#define TEST_RELEASE(object) ({ if (object) [object release]; })
which doesn't provide that.
Thanks,
RELEASE was introduced to completely remove the call to -release in
the case when gc was enabled. Apple have now effectively done the
same thing by modifying the compiler to remove the call itsself... we
went for a more portable solution, but as they control the compiler
version being used, Apples decision makes a lot of sense.
TEST_RELEASE was added to optimise the common case of sending -release
to nil when gc was not enabled ... the 'if (object)' test being much
more efficient than a method call.
Neither optimisation is really important IMO, now that processors are
*much* faster than they were when these macros were introduced. The
overheads of calling -release are generally a much smaller proportion
of the overall running time of a program than they used to be.
I think the ASSIGN, ASSIGNCOPY, and DESTROY macros are still
worthwhile having as conveniences (and because they tend to prevent
some common coding errors).
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