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Date: Wed, 17 Mar 2010 15:41:18 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] [PATCH] [TRIVIAL] usb-linux: remove unreachable
	default in switch statement
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To: Blue Swirl <blauwirbel@gmail.com>
Cc: Paul Bolle <pebolle@tiscali.nl>, Paul Brook <paul@codesourcery.com>, qemu-devel@nongnu.org

On 03/17/2010 03:15 PM, Blue Swirl wrote:
> On 3/17/10, Paul Brook<paul@codesourcery.com>  wrote:
>    
>>>> If something should never happen (as in this case) then an abort/assert
>>>>          
>>   >  >  is completely appropriate. Once things get that screwed up there's no
>>   >  >  right answer, and the best thing we can do is terminate immediately to
>>   >  >  try and avoid further damage.
>>   >
>>   >  This case was:
>>   >
>>   >  switch (foo&  0x03) {
>>   >  case 0: case 1: case 2: case 3:
>>   >  default:
>>   >  }
>>   >
>>   >  The default is unreachable.  Having it there just introduces more code
>>   >  that serves no purpose.  Unless someone does something totally foolish
>>   >  and changes the mask in the switch statement, there's no way it will
>>   >  ever be reachable.
>>
>>
>> I mistakenly remembered this was using a symbolic mask rather than a literal
>>   0x03. In that case I'd argue it's much easier to make the dumb error you
>>   describe, and the assert can be a handy cluebat.
>>
>>   I guess it's largely personal preference - I prefer to add the default case to
>>   make it clear that falling through is never gong to be the right answer.
>>      
> This breaks build (gcc 4.3.2):
>    CC    usb-linux.o
> cc1: warnings being treated as errors
> /src/qemu/usb-linux.c: In function 'usb_linux_update_endp_table':
> /src/qemu/usb-linux.c:759: error: 'type' may be used uninitialized in
> this function
>    

That's unfortunate.  I'll revert.

Regards,

Anthony Liguori