[Development] Fwd: Change in qt/qtbase[dev]: Enable -Werror for all of qtbase

Konstantin Ritt ritt.ks at gmail.com
Sun Sep 8 22:21:10 CEST 2013


Whilst I'm with Oliver and André in that part that affects the Qt user (and
I can imagine users in panic filing "latest dev build fails" bugs right
now), I agree with Thiago in that part that we could try fixing existing
warnings on some configurations at very least.
Throwing warnings is not a way for compiler to simply bother you, most
often warnings are "almost errors". I.e. if compiler says there is a
possible issue, go and check it.

Despite that fact we all don't like wasting our time, several potential
issues were fixed already (i.e. 5dd2713c8ba98e06ae5c4f3da44b2ed73121d247 );
so let's give it a try for a short time, at least.
However, I'd like to ask someone to blog about this experiment and show the
user how to switch -Werror of at configure time.

Kind regards,
Konstantin

2013/9/5 Thiago Macieira <thiago.macieira at intel.com>

> On quinta-feira, 5 de setembro de 2013 09:41:11, Giuseppe D'Angelo wrote:
> > On 5 September 2013 08:44, Thiago Macieira <thiago.macieira at intel.com>
> wrote:
> > > Can we please give the feature a try, for a week or two, with
> > > -warnings-are- errors enabled in all CI builds?
> >
> > I don't think this is the point. We already do have several
> > -developer-build configurations active in CI, and, as you say, that's
> > enough for enabling -Werror there. Eventually, the configurations
> > without -developer-build could get -warnings-are-errors, but that's
> > another story...
>
> That's part of what I am asking.
>
> > The problem (*) is that the CI is not testing common configurations
> > that developers use daily, for instance GCC 4.7/4.8 under Linux. If a
> > patch of mine triggers warnings (= errors) under one of those
> > compilers, but not for the other compilers used by CI (see [1]) it
> > will get merged. And as soon as the other hundred developers pull the
> > branches with that patch, they'll have a broken build, and they'll
> > have to act to solve / work around the warning (instead of doing their
> > job [2]).
> >
> > That's why I was proposing to limit the -Werror to those compilers
> > which are actually in the CI, so those patches don't get merged in the
> > first place and the *submitter* is forced to act to solve the warning:
>
> I disagree. That's why I am asking for two weeks of testing.
>
> I don't think -Werror are any worse than any other changes going on. Let me
> give you several examples:
>
> 1) developer A writes code on Ubuntu, for example the same version that we
> have on CI. It compiles, so it gets integrated. Developer B gets the code
> and
> is running brand-new Gentoo or Fedora Rawhide, with glibc 2.19-pre. Code
> fails
> to compile because glibc removed an indirect include.
>
> This has happened in the past, just with different version numbers.
>
> 2) developer A submits code that uses non-standard header names and bad
> include guards, and it passes CI integration. Developer B downloads the
> code
> and does some extra checks, causing the problems to show.
>
> Developer A = Lars & Simon, the code was V4.
>
> 3) code exists in the Qt repositories and compiles on all compilers we've
> so
> far tested. A new compiler version is released, so we test and find that it
> fails to compile due to a stricter checking of some C++ feature.
>
> This has also happened in the past, like with aliasing violations.
>
> My points are:
> * The CI can *never* check everything. We rely on crowdsourcing by our own
>   devs to catch those mistakes.
> * New compilers need to be validated anyway.
> * Upgrades of third-party libraries can cause build failures anyway.
>
> So I am asserting here that -Werror is no different from the cases above.
> The
> issues we're seeing now is that we've only had a limited time to fix the
> *existing* warnings. That's why I am asking for one or two weeks, so we
> find
> out how often this continues to happen, after the initial warnings get
> fixed.
>
> --
> Thiago Macieira - thiago.macieira (AT) intel.com
>   Software Architect - Intel Open Source Technology Center
>
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>
>
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