RE: floatValue of nil NSNumber unreliable (was Re: Bug or feature?)
RE: floatValue of nil NSNumber unreliable (was Re: Bug or feature?)
- Subject: RE: floatValue of nil NSNumber unreliable (was Re: Bug or feature?)
- From: Guy English <email@hidden>
- Date: Tue, 14 Feb 2006 13:33:12 -0500
On Tuesday, February 14, 2006, at 01:32PM, M. Carlson <email@hidden> wrote:
>>From this Apple statement:
>
>"The Objective-C runtime assumes that the return value of a message sent to
>a nil object is nil, as long as the message returns an object or any integer
>scalar of size less than or equal to sizeof(void*)."
>
>Would it be fair to conclude that a float value takes up more stack space
>than an integer, and thus the "odd" behavior? I.e., it's only zeroing out
>space enough for an integer, not a float value, so whatever's sitting beyond
>the integer on the stack is being returned as part of the float value?
>
>--M
>
>
>From: Daniel Jalkut <email@hidden>
>To: M. Carlson <email@hidden>
>CC: email@hidden
>Subject: floatValue of nil NSNumber unreliable (was Re: Bug or feature?)
>Date: Tue, 14 Feb 2006 13:21:55 -0500
>
>Interesting. I just took your snippet and also reproduced funny behavior
>(identical config to yours, incidentally).
>
>What's interesting is the "random number" seems to correspond to the last
>"real float NSNumber" used.
>
>For instance:
>
> float fval=0.0;
> NSNumber *aNumber=nil;
> NSNumber *secondNumber = [NSNumber numberWithFloat:0.5];
> fval=[aNumber floatValue];
> NSLog(@"fval is %f",fval);
>
>fval is always 0.5.
>
>It sounds like a bug to me. Maybe somebody from Apple will have an opinion
>about this.
>
>Daniel
>
>On Feb 14, 2006, at 1:14 PM, M. Carlson wrote:
>
>>This is using Xcode 2.2, OSX 10.4.4, PM G5 2GHz x 2. When I run this, I
>>get random numbers in fval. This came about when I was retrieving a value
>>from an NSDictionary, but there was no entry in the dictionary for the key
>>I was using. I ended up getting wild values for fval, and finally boiled
>>it down to this little snippet, which seems odd to me.
>>
>>So, am I misunderstanding something about Cocoa, or is it some Xcode
>>setting I'm supposed to be using so I get 0 back?
>
>
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