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From: ike@localhost.claranet.nl (Ike Naar)
Newsgroups: comp.compilers
Subject: Re: GCC/G++ compiler: Error goes away when run through debugger
Date: Tue, 29 Mar 2011 21:42:12 +0000 (UTC)
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George Neuner  <gneuner2@comcast.net> wrote:
>GCC's -O3 optimization level is widely known to cause strange problems
>... almost always because the program is violating assumptions made by
>the more advanced optimizations.
>
>The -O2 level typically is safe.  If you think you need the -O3
>optimizations, you should individually enable them to see if any
>breaks the program.  Specify -O3 only if you find they all work.

Sometimes using -O3 makes the program run slower than when using -O2.