Re: -Wall
Re: -Wall
- Subject: Re: -Wall
- From: Alastair Houghton <email@hidden>
- Date: Thu, 5 Jun 2008 11:56:11 +0100
On 5 Jun 2008, at 01:15, Stuart Malin wrote:
I'm curious of the efficacy of doing so. For instance, even with -
Wall, some of my lazy coding styles, e.g.:
if (anInstance = [enumerator nextObject]) doSomethingWithAnInstance;
generated warnings and I was led to code such as:
if ((anInstance = [enumerator nextObject]) != nil)
doSomethingWithAnInstance;
I guess this makes explicit my intent, and so can be argued this is
better coding practice...
FWIW, it's sufficient to write
if ((anInstance = [enumerator nextObject)) doSomethingWithAnInstance;
The extra "!= nil" isn't required, though some people think it's
clearer (it isn't *my* cup of tea, mind, not least because I think
attempts to make C "easier to read" just encourage people not to learn
C properly.)
It's quite possible to write warning-free code even with relatively
high warning levels (I tend to go for "-W -Wall" and I have a zero-
tolerance approach to warnings), which brings me to:
On 5 Jun 2008, at 01:33, Jean-Daniel Dupas wrote:
Some warning like unused param should be ignored (and so disabled).
You're right in general that some warnings are a little pointless, but
the unused parameter warning *is* actually a useful one. It has
occasionally saved me considerable headaches where either (a) I'd
forgotten to implement part of a function I was writing, or (b) I'd
mis-spelt one of the parameter names, and it just so happened that
there was already a variable with the other name I'd accidentally used.
On 5 Jun 2008, at 02:53, Alex Curylo wrote:
Option A) which I use since it works with compilers from that other,
lesser, platform most people write code for:
- (void)emptyMethod:(NSNotification*)notification
{
(void)notification;
}
Or the slightly better version that works everywhere *and* makes it
clear that something is unused:
#define UNUSED(x) (void)(x)
...
- (void)emptyMethod:(NSNotification *)aNotification
{
UNUSED (aNotification);
}
Option B) when you can assume the requirement of compilers which do
not suck:
- (void)emptyMethod:(NSNotification*)notification
{
#pragma unused (notification)
}
The advantage (which nobody seems to have mentioned) of the pragma or
the GNU __attribute__((__unused__)) being that the compiler should
then tell you if you've declared something unused and it, in reality,
*is* being used somewhere.
It's a little unfortunate that it isn't possible to #define something
to a pragma prior to C99, but as of C99 you can even do something like
(written in Mail and not tested):
#if __STDC_VERSION__ >= 199901L && __APPLE__
#define UNUSED_PRAGMA(x) _Pragma(#x)
#define UNUSED(x) UNUSED_PRAGMA(unused (x))
#else
#define UNUSED(x) (void)(x)
#endif
which will use the pragma where it's supported and fall back to the
old-fashioned cast-to-void where it isn't.
Kind regards,
Alastair.
--
http://alastairs-place.net
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