Re: Arc: Switch case is in protected scope
Re: Arc: Switch case is in protected scope
- Subject: Re: Arc: Switch case is in protected scope
- From: ChanMaxthon <email@hidden>
- Date: Tue, 22 Oct 2013 16:06:04 +0800
Compiler issue. All cases in a switch statement shares a same scope, and ARC works by inserting code into beginning and end of scopes. switch() statement jumps around, making code path very unpredictable, confusing ARC.
Sent from my iPhone
> On 2013年10月22日, at 16:02, "Gerriet M. Denkmann" <email@hidden> wrote:
>
>
>> On 22 Oct 2013, at 14:48, ChanMaxthon <email@hidden> wrote:
>>
>> Just put a set of braces after every case: and it should be okay. A set of braces here actually sets up a mini stack frame that makes ARC work.
>
> 非常感谢
> Works perfectly now.
> (I still would like to know whether my code was faulty, or whether this is a compiler bug)
>
>
> Kind regards
>
> Gerriet.
>
>>> On 2013年10月22日, at 15:41, "Gerriet M. Denkmann" <email@hidden> wrote:
>>>
>>> Converting to Arc (Xcode 5.0).
>>>
>>> This works fine without Arc (regardless whether TRIGGER_ERROR is defined or not):
>>>
>>> NSMutableString *mus = [ NSMutableString string ];
>>> NSString *word = @"abc";
>>>
>>> switch( self.colourType )
>>> {
>>> case colour_link:
>>> [ mus appendString: @"<a href=\"" ];
>>> #define TRIGGER_ERROR
>>> #ifdef TRIGGER_ERROR
>>> NSString *urlStr = [ word stringByAddingPercentEscapesUsingEncoding: NSUTF8StringEncoding ];
>>> [ mus appendString: urlStr ];
>>> #else // no_ERROR
>>> [ mus appendString: [ word stringByAddingPercentEscapesUsingEncoding: NSUTF8StringEncoding ] ];
>>> #endif // no_ERROR
>>>
>>> break;
>>>
>>> default:
>>> [ mus appendString: word ];
>>> };
>>>
>>> But with Arc, if TRIGGER_ERROR is defined, I get an error: "Switch case is in protected scope" with the further explanation: "Jump bypasses initialization of retaining variable".
>>>
>>>
>>> Was the old (non-arc) code faulty (but the compiler did not notice this)?
>>> Why is the arc-version (with TRIGGER_ERROR defined) wrong?
>
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