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

[Khem Raj]

On Thu, Aug 29, 2019 at 1:25 PM Adrian Bunk <bunk at stusta.de> wrote:
>
> 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 at 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 at 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 at 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.
>

which is fine, since we can report it upstream to either gcc if its
gcc's fault or to package itself
and better still with a patch. Ideally we should use package defaults
or maybe be more strict
 If everyone stop using these warnings then why is compiler adding
them in the first place
here I realize lies the difference of opinion.

> 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]
>

maybe you should explain a bit more why they not correct
these patches are to define local gettid function if system libc does
not provide it
there is a new syscall wrapper in glibc 2.30, older glibcs wont have it.

> cu
> Adrian
>
> [1] pid_t is an int in glibc, which makes the lack of prototypes
>     harmless in this specific case.
>
> --
>
>        "Is there not promise of rain?" Ling Tan asked suddenly out
>         of the darkness. There had been need of rain for many days.
>        "Only a promise," Lao Er said.
>                                        Pearl S. Buck - Dragon Seed
>