Date: Sat, 10 Jun 2017 15:24:01 -0700 From: Patrick Mahan <mahan@mahan.org> To: FreeBSD Mailing List <freebsd-questions@freebsd.org>, serpent7776@gmail.com Subject: Re: -O2 flag Message-ID: <dbe711db-2090-6e61-9306-4e451317098f@mahan.org> In-Reply-To: <20170610230928.581e3cf9@DaemONX> References: <593C4679.5010104@gmail.com> <20170610230928.581e3cf9@DaemONX>
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On 6/10/17 2:09 PM, Serpent7776 wrote: > On Sat, 10 Jun 2017 16:20:25 -0300 > Friedrich Locke <friedrich.locke@gmail.com> wrote: > >> Hi folks, >> >> i am trying compile a program with cc on freebsd 11. >> When i use -O2 compilation flag, the compiled code is giving error on >> execution, but with i omit -O2 everything works ok. >> >> Have anybody already faced such problem ? > Yes, a few times in the past. Your code may have hidden bug which is triggered > only with optimizations enabled. It might be relying on some kind of undefined > behaviour. > Unfortunately, I don't have any helpful advices on how to find this error - > try enabling all compiler warnings flags. > I'd suspect a bug in your code rather than a bug in compiler, but the latter is > not impossible. > This is especially noticeable when you use uninitialized stack variables in a function. Non-optimized generally gets you a cleaner stack. But I've seen code that assumes a stack variable always has a certain value. Patrick
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