Re: [meta-oe][PATCH] libwebsockets: Fix the build with -Os

[Adrian Bunk <bunk@stusta.de>]

On Thu, Aug 29, 2019 at 12:54:16PM -0700, Khem Raj wrote:
> On Thu, Aug 29, 2019 at 12:14 PM Adrian Bunk <bunk@stusta.de> wrote:
> >
> > On Thu, Aug 29, 2019 at 11:46:55AM -0700, Khem Raj wrote:
> > > On Thu, Aug 29, 2019 at 3:39 AM Adrian Bunk <bunk@stusta.de> wrote:
> > > >
> > > > lib/event-libs/libuv/libuv.c: In function 'elops_destroy_context1_uv':
> > > > lib/event-libs/libuv/libuv.c:519:7: error: 'm' may be used uninitialized in this function [-Werror=maybe-uninitialized]
> > > >     if (m)
> > > >        ^
> > > >
> > > > Signed-off-by: Adrian Bunk <bunk@stusta.de>
> > > > ---
> > > >  .../recipes-connectivity/libwebsockets/libwebsockets_3.1.0.bb   | 2 ++
> > > >  1 file changed, 2 insertions(+)
> > > >
> > > > diff --git a/meta-oe/recipes-connectivity/libwebsockets/libwebsockets_3.1.0.bb b/meta-oe/recipes-connectivity/libwebsockets/libwebsockets_3.1.0.bb
> > > > index 50620d99e..fcabeb902 100644
> > > > --- a/meta-oe/recipes-connectivity/libwebsockets/libwebsockets_3.1.0.bb
> > > > +++ b/meta-oe/recipes-connectivity/libwebsockets/libwebsockets_3.1.0.bb
> > > > @@ -28,3 +28,5 @@ EXTRA_OECMAKE += " \
> > > >  PACKAGES =+ "${PN}-testapps"
> > > >
> > > >  FILES_${PN}-testapps += "${datadir}/libwebsockets-test-server/*"
> > > > +
> > > > +CFLAGS_append = " -Wno-error"
> > >
> > > is it possible to fix the underlying problem? since Os is not default
> > > it definitely could be a bug in upstream but
> > > by disabling warnings for all kind of builds we are  painting with broad brush
> >
> > The underlying problem is that some gcc warnings are not reliable with -Os,
> > there are bugs open in the gcc bugzilla for that.
> >
> I am aware of that for maybe-* warnings heuristics may go wrong, but
> then its better to just disable that
> one warning from being treated as error if thats possible to add
> easily something like
> -Wno-error=maybe-uninitialized could do it.

And then the package fails to build due to a different warning after the 
next gcc upgrade.

The few packages that manually set -Werror are causing so much trouble,
and seeing warnings as errors in this code from 2018 that is currently
298 commits behind upstream master won't bring actual benefits even
when the warnings are not gcc bugs.

If you are interested in warnings you shouldn't have -Werror in very few 
packages, but check for the most problematic warnings in all packages.

E.g. -Wimplicit-function-declaration warnings are often the cause for
runime crashes, and a quick grep through my build logs shows that your
gettid patches to snort/lttng-tools/lttng-ust are not correct.[1]

cu
Adrian

[1] pid_t is an int in glibc, which makes the lack of prototypes
    harmless in this specific case.

-- 

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        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed