Re: Meson build

On Tue, Sep 01, 2020 at 03:50:36PM +0200, Ján Tomko wrote: > On a Tuesday in 2020, Pavel Hrdina wrote: >> On Tue, Sep 01, 2020 at 03:13:39PM +0200, Ján Tomko wrote: >>> On a Tuesday in 2020, Pavel Hrdina wrote: >>>> On Sun, Aug 30, 2020 at 02:34:56AM +0200, Toolybird wrote: >>>>> Hi, >>>>> >>>>> Just a heads up on my experiences with the new build system. >>>>> >>>>> Arch Linux >>>>> meson-0.55.1 >>>>> >>>>> Overall, it looks good, so well done! >>>>> >>>>> Just a couple of minor things I noted: >>>>> >>>>> 1. Arch uses a meson wrapper script (arch-meson) that sets: >>>>> >>>>>   --buildtype plain >>>>> >>>>> This seems to trigger a bug in meson that results in copious bogus compiler warnings: >>>>> >>>>> cc1: warning: ‘-Wformat-y2k’ ignored without ‘-Wformat’ [-Wformat-y2k] >>>>> cc1: warning: ‘-Wformat-extra-args’ ignored without ‘-Wformat’ [-Wformat-extra-args] >>>>> cc1: warning: ‘-Wformat-zero-length’ ignored without ‘-Wformat’ [-Wformat-zero-length] >>>>> cc1: warning: ‘-Wformat-contains-nul’ ignored without ‘-Wformat’ [-Wformat-contains-nul] >>>>> cc1: warning: ‘-Wformat-security’ ignored without ‘-Wformat’ [-Wformat-security] >>>>> >>>>> which of course breaks -Werror builds. >>>>> >>>>> I can easily work around it by setting `-D git_werror=disabled' or even better still: >>>>> >>>>> CFLAGS+=" -Wall" arch-meson... >>>> >>>> This should be easily fixable by adding -Wformat in our list of flags >>>> that we pass to compiler. We were incorrectly relying on meson to add >>>> -Wformat automatically and since we add the other -Wformat* flags >>>> manually we should add -Wformat as well. I'll post a patch to fix this. >>>> >>> >>> What would that fix? >>> >>> It would neither be a plain build, nor a full -Werror build (since we're >>> missing -Wall). >> >> It would fix building libvirt from git in case user uses >> buildtype=plain. >> > > For a build from git, we expect people to build with all the warnings > and -Werror. > > Per your comment in the below issue: > https://github.com/mesonbuild/meson/issues/7399#issuecomment-684856012 > meson does not add the warnings there on purpose. > > The combination of disabling the most important warnings and enabling > just the extras doesn't make much sense. Especially if we still pretend > it's a -Werror build. Yeah, I'd recommend distros to NOT use buildtype=plain.

Having the full set of warnings including -Werror enabled is a good thing in general, even for distros. There have certainly been cases where distros backported a patch incorrectly and warning flags would have identified it, especially combined with -Werror.