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Subject: Re: [PATCH] Fix -Os related -Werror failures.
To: Arnd Bergmann <arnd@arndb.de>, libc-alpha@sourceware.org
References: <6eac682f-26fa-6a47-9497-357206266ba1@redhat.com>
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 <20863164.XNWC5rYB1g@wuerfel>
Cc: Jeff Law <law@redhat.com>, Florian Weimer <fweimer@redhat.com>,
 Carlos O'Donell <carlos@redhat.com>
From: Paul Eggert <eggert@cs.ucla.edu>
Message-ID: <7820c555-1463-6c3a-17e5-650a44fabd19@cs.ucla.edu>
Date: Fri, 28 Oct 2016 20:10:00 -0000
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On 10/28/2016 01:12 AM, Arnd Bergmann wrote:
> I found that most often when gcc is confused about whether a variable is uninitialized or not, the source code tends to be confusing to a human reader as well and rewriting it differently results in better readability and better object code while avoiding the warning.

I'm afraid my experience has not been so good. Maybe 1/3 of the time rewriting is better, but otherwise rewriting doesn't help or even confuses the code. When that happens with -Wmaybe-uninitialized, in Emacs we typically use C declarations like this:

       ptrdiff_t offset2 UNINIT; /* The UNINIT works around GCC bug 
78081.  */

where UNINIT is defined something like this:

   #ifdef GCC_LINT
   # define UNINIT = {0,}
   #else
   # define UNINIT /* empty */
   #endif

and configuring with --enable-gcc-warnings compiles with something like 
'gcc -Wall -Werror -DGCC_LINT'.