> On Sep 13, 2018, at 12:03 PM, Fabian Groffen <grob...@gentoo.org> wrote:
> 
>> On 13-09-2018 07:36:09 -0400, Richard Yao wrote:
>> 
>> 
>>>> On Sep 12, 2018, at 6:55 PM, Thomas Deutschmann <whi...@gentoo.org> wrote:
>>>> 
>>>> On 2018-09-12 16:50, Rich Freeman wrote:
>>>> There is also the case where we want these warnings to block
>>>> installation, because the risk of there being a problem is too great.
>>> 
>>> I really disagree with that. So many devs have already said multiple
>>> times in this thread that "-Werror" is only turning existing warnings
>>> into fatal errors but "-Werror" itself doesn't add any new checks and
>>> more often requires "-O3" to be useful.
>> The way that compilers work is that the warnings are generated in the front 
>> end while the optimization level affects the backend. That means that -O3 
>> has no effect on the code that does error generation. This remark about -O3 
>> being needed to make -Werror useful is just plain wrong. 
> 
> Huh?  -O3 enables more checks, which can generate more warnings.

What checks are those? -O3 affects backend optimization while warnings are 
generated by the front end. Once the immediate representation is generated, 
there are no other warnings aside from those from the linker.
>  -O3
> isn't "needed", but if upstream is so interested in clean and correct
> code, they should've fixed all warnings in the first place and thus
> enabled all of them.  In fact, I expect every sane upstream to use "-O3
> -Wall -Werror" in one of their automated builds.  Not that this catches
> anything useful on x86{,_64} when there is for instance use of signed
> and unsigned char types, so it isn't conclusive.
> 
> The whole point in here is that -Werror doesn't add much if you care.
> The whole point why it is not desired in Gentoo is that users don't
> necessarily are developers, or even interested in fixing warnings --
> regardless whether they point to real problems or not.
> 
> If there are real problems in a package (exposed by a compiler or not)
> then this should ideally stand out during ~arch testing, or even before
> when the Gentoo maintainer examines the build (might even use -Werror
> for his own purposes).  If such code ends up in stable arch we just made
> a stabilisation mistake, or got royally messed up by upstream, depending
> how you look at it.
> 
> Fabian
> 
> -- 
> Fabian Groffen
> Gentoo on a different level


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