Fedora's Mesa Drivers Have Been Running Slower As They Were Accidentally Debug Builds

[Tim4]

IMO first who spotted this bug this person https://bugs.freedesktop.org/show_bug.cgi?id=109939

[andreano]

Why -Db_ndebug=true and not -Dbuildtype=release (as even suggested in the report)?

[dungeon]

Why -Db_ndebug=true and not -Dbuildtype=release (as even suggested in the report)?

Because *only* explicit -Db_ndebug=true disables assertions, with meson that is not automatic like with autotools

-Db_ndebug This option controls assertions in meson projects. When set to false (the default) assertions are enabled, when set to true they are disabled. This is unrelated to the buildtype; setting the latter to release will not turn off assertions.

https://www.mesa3d.org/meson.html

[aejsmith]

Because *only* explicit -Db_ndebug=true disables assertions, with meson that is not automatic like with autotools



https://www.mesa3d.org/meson.html

I think that documentation is actually incorrect - Mesa has b_ndebug defaulting to if-release, which will disable asserts for buildtype=release. Just wasn't doing so for buildtype=plain, though a Meson PR has been posted to include plain as part of if-release: https://github.com/mesonbuild/meson/pull/5143

[dungeon]

I think that documentation is actually incorrect

I don't care about that really , file a bug for doc if you think that is the case

Let alone that Meson's release buildtype assumes O3 and that is something not recommended for building Mesa for distros... with that some users will have a bug which is not a bug General purpose binary distros should go with plain O2 generic nondebug plus distro flags

[FireBurn]

IMO first who spotted this bug this person https://bugs.freedesktop.org/show_bug.cgi?id=109939

Who didn't hit the issue because their distro did the right thing already

[wizard69]

Whoops!!

Mistakes happen.

[sa666666]

Is there any way to test whether a Mesa build was built properly (other than by benchmarks, of course)?

[treba]

If I understand things right, this is a meson bug. So it could affect many more packages, like the gnome shell.

[andreano]

meson bug

If they actually set buildtype to release, then I agree, but if they set it to plain, or even left it at the default (which is debug), then they simply got what they asked for.

EDIT:
I just tested Meson 0.45.1, and --buildtype=release (which is the right way to set buildtype to release) does not define NDEBUG on the compiler command. This is contrary to my expectation, confirms what dungeon wrote, and implies that the documentation was correct after all – it wasn't a bug.