On Tue, 8 Feb 2011 17:07:00 -0600, Fritz Anderson <fri...@manoverboard.org> said: >On 8 Feb 2011, at 2:51 PM, Quincey Morris wrote: > >> P.S. It's OT, but initializing 'error' to nil before passing it to an >> error-returning method is both a waste of time and semantically incorrect -- >> it's an *output only* parameter to the method. OTOH, setting it to nil isn't >> inherently harmful. :)
We've been through this many times before, and I'm going to quote two different views (from this list, October 2009) that seem to me definitive. They are commenting on this code: > NSStringEncoding enc = nil; > NSError *error = nil; > > NSString *file = [NSString > stringWithContentsOfFile:@"/Users/colin/developer/Trace/glass.csv" > usedEncoding:&enc error:&error]; From Bill Bumgarner: > If the method fails -- if file is nil -- the 'error' will be filled in > with an [autoreleased] NSError instance describing the error. > However, 'enc' will be undefined. > > If the method succeeds, file and enc will be non-nil references to the > result, but 'error' will be undefined. > From Ben Trumbull, in response: > Not initializing locals is imho, > professionally, realistically, and morally wrong. It's just a bug > waiting to happen. And you have to know it is, just looking at it. > Whatever might have been saved / gained by not initializing them was > wasted, for all of time, the first time I had to debug the segfault. So the take-home message is: To touch "error" after this call without first learning that "file" is nil is wrong and can lead to undefined behavior. But not to initialize a local pointer variable is an accident waiting to happen. So my rule is: do initialize "error" to nil, but then follow the rules about when it is safe to touch. m. -- matt neuburg, phd = m...@tidbits.com, <http://www.apeth.net/matt/> A fool + a tool + an autorelease pool = cool! AppleScript: the Definitive Guide - Second Edition! http://www.apeth.net/matt/default.html#applescriptthings_______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
