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To: <zsh-workers@zsh.org>
Subject: Re: PATCH: fix occasional warning
References: <op.vwncswxenba3tw@pwspc01.europe.root.pri>
 <20110606113255.GA8105@prunille.vinc17.org>
Date: Mon, 6 Jun 2011 12:46:53 +0100
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From: Peter Stephenson <pws@csr.com>
Organization: Cambridge Silicon Radio
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On Mon, 06 Jun 2011 12:32:55 +0100, Vincent Lefevre <vincent@vinc17.net>  
wrote:
> On 2011-06-06 10:03:58 +0100, Peter Stephenson wrote:
>> The code here is actually safe, but some (now old) versions of gcc
>> produce a warning anyway.  Better to rely on more recent versions
>> optimising out the unused value.
>
> But recent or future GCC versions may warn against values set but
> unused.

The code is of this form:

   uint16 value = 0; /* this is strictly unnecessary */
   uint16 value_set = 0;

   if (some_test)
   {
      value = some_value;
      value_set = 1;
   }
   /* ... */
   if (value_set)
   {
      do_something_with(value):
   }

If compilers start warning about unused initialisation to
value in a case like this, I for one will get very cross.
It is having no other effect than making it hard for you
to write safe, portable code.

pws


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