Segmentation faults with Mutter 47/48 on Gentoo

[pimvullers]

What Happened?

Using Gala 8.4.0. Gala works fine when built against mutter-46.
When starting gala on Gentoo when built against mutter 47 or 48, it crashes.

Today I spent some time to debug and located a few cases where segfaults are generated:

1. Cogl.color.from_string("Black") --> based on default mutter/cogl documentation this expects a color code (RGB/RGBA/HSL) instead of a name. Replacing "Black" with "#000" resolves the segfault.

2. BackgroundBlurEffect Clutter actor does not seem to have a context. below "patches" cause to proceed in the gala startup, but then I get another segfault when the object is created by the BlurManager (see attached gdb backtraces). Not sure whether the get_context() replacements have a meaningful effect, but it looked cleaner to me in my attempt to analyze the problem. quick fix for window switcher was just to remove the effect.

   sed -i -e "s/Black/#000/" src/Background/BackgroundContainer.vala
   sed -i -e "s/actor.context/actor.get_context()/" src/Background/BlurEffect.vala
   sed -i -e "s/actor.context/actor.get_context()/" src/BackgroundBlurEffect.vala
   sed -i -e "/blur_effect/d" src/Widgets/WindowSwitcher/WindowSwitcher.vala
   sed -i -e "s/black/#000/" src/Widgets/SessionLocker.vala

Steps to Reproduce

1. Build gala against unpatched mutter-48 (I'm using 48.5)
2. Start gala (I'm using gdb --args gala --replace)
3. Attached backtraces from the fails (for the various cases).

bt.txt

Expected Behavior

Gala starts fine without segfaults, like it does with mutter-46.

OS Version

Other Linux

OS Architecture

amd64 (on most hardwares)

Session Type

Secure Session (Wayland, This is the default), Classic Session (X11)

Software Version

Latest release (I have run all updates)

Log Output

See attached bt.txt, let me know if other specific logs are helpful.

Hardware Info

No response

[pimvullers]

for the cogl color from_string topic, the C API actually returns a boolean, whether the conversion succeeded or not. At Vala level this is translated to either return the constructed color struct, or NULL. So the alternative would be to create a wrapper with a fallback, as I just noticed that there are multiple locations where the from-string conversion is used, also based on settings values (so input not under control of the code), and as such it would make more sense to validate the input or the produced output.

[leolost2605]

Hi thanks for the detailed report! Both crashes have been fixed in #2708 and #2710 respectively so on main it shouldn't crash anymore :)

[pimvullers]

Thanks, i will give it a try by building from latest git, and if it works add those 2 patches to the gentoo packaging of gala.

[pimvullers]

Confirmed that using git version works. Will work on the patches for 8.4.0 to provide a clean package.

Are you aware of any similar activities for the greeter? As that still seems to fail with mutter-47/48 (and works fine with mutter-46). That one is also a bit harder to debug.