Re: [gentoo-dev] Changing policy about -Werror

[Jason Zaman]

On Mon, Sep 10, 2018 at 01:51:15PM -0700, Matt Turner wrote:
> On Mon, Sep 10, 2018 at 1:34 PM Chí-Thanh Christopher Nguyễn
> <chithanh@g.o> wrote:
> >
> > Jason Zaman schrieb:
> > >> No. With -Werror, upstream indicates that if a warning occurs, the build
> > >> should fail and the resulting code not be installed on user systems.
> > >>
> > >> Instead, someone knowledgeable should look at the situation *first* and
> > >> determine whether it is a bogus warning, a trivial issue, or something which
> > >> warrants further attention.
> > >>
> > >> I have long disagreed with QA policy on this, and think that ebuilds should
> > >> respect upstream here. Of course giving users the ability to override.
> > >
> > > I disagree. -Werror means that upstream wants it to build without
> > > warnings on their distro with their version of the compiler with their
> > > versions of all the libraries.
> >
> > It means, upstream wants it to build without warnings everywhere. And if a
> > warning occurs (due to change in compiler, libraries, architecture, etc.),
> > have a developer look at it first before installing the code on user systems.
>
> This sounds good in theory, but I think it's pretty well established
> that in practice this isn't effective and instead is a large waste of
> time. In fact, the foundational premise that it's possible to build
> without warnings everywhere is simply wrong.
>
> Consider again the bug that started this. The maintainer had not built
> this configuration. None of the arch teams had built this
> configuration until I did for the last architecture Cc'd. The patch
> committed doesn't change anything installed on the system, if not for
> Werror preventing the code from building.

Replying to a somewhat random post. There are two separate things here
that people are discussing here but are not the same thing.

1) We want to know when a package has terrible warnings when installing
it so we can report upstream and know that something might have gone
wrong.

2) There are a lot of spurious warnings that are worthless and would
just annoy *everyone*. They are still legit warnings so its not like
they should go away but they should not break the build.

-Werror trips up on both of these which is why everyone dislikes it.
We want to inform people about only 1) not 2). The solution to this is
https://gitweb.gentoo.org/proj/portage.git/tree/bin/install-qa-check.d/90gcc-warnings
(There is also an equivalent clang-warnings check too). These spit out 
"QA Notice: Package triggers severe warnings which indicate that it may
exhibit random runtime failures." and a huge list of them.

These are a focused list of the worst warnings that should be fixed
first before all the others. If your goal is to improve the quality of
code in general this qa-check is much better than using Werror on
everything.

Stick this in your make.conf:
PORTAGE_ELOG_SYSTEM="echo save"
PORTAGE_ELOG_CLASSES="warn error log qa"
I'm pretty sure toralf's tinderbox already has these enabled but all
devs should too.

-- Jason