Meson build

[Ján Tomko]

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).

>> Maybe this github issue is related?:
>>
>> https://github.com/mesonbuild/meson/issues/7399
>>
>> 2. Arch currently builds libvirt with support for ZFS. Seeing as ZFS is not in the distro proper, a simple Autoconf tweak is used:
>>
>> ZFS=/usr/bin/zfs ZPOOL=/usr/bin/zpool \
>> ./configure ...
>>
>> This is surprisingly hard to emulate with meson, in fact it appears impossible, unless I resort to dodgy hacks with sed etc.
>
>I'm not sure I understand the reasoning behind this.
>
>For normal usage users of libvirt should not fake that something exists
>to make libvirt building the support for it because obviously it will
>not work.
>
>If you are asking from packager POV you should add ZFS as regular build
>dependency and also run dependency.
>

If it's possible to fake it, it's not a build dependency.

Jano

>I'm looking into the arch linux packaging and if that's your concern I
>guess you should create libvirt-storage-zfs sub-package like it is done
>for gluster, iscsi-direct and rbd.
>
>Pavel


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