X11 PRIME detection logic leaks memory according to Valgrind

[qarmin]

Godot version:
3.2.dev.custom_build. 0d61fc2

OS/device including version:
Ubuntu 19.04, Gnome 3.32.1, GTX 970 Proprietary drivers 430.26

Issue description:
When I check Godot(now open only project manager, but same is with editor and game) with simple Valgrind 3.14 command then in log is shown a lot of leaked memory - valgrindDefinite.txt

valgrind --log-file="~/valgrind.txt" --leak-check=full --show-leak-kinds=definite godot

Also changing definite option to all increase number of possibly leaks - valgrindALL.txt

I'm not sure if that are Godot or hardware/Valgrind issue, so I tried to check Godot on my laptop with Intel HD 3000 and Mesa 19 but warnings are same as in issue #16214

[ibrahn]

The majority of the leaks logged are from a sub-process. (I think in this case, the one forked for PRIME gpu detection.)
This happens because we exit in the worker process and so the cleanup of allocations made before the fork doesn't happen on that side. Probably sensible, because it helps avoid triggering a copy-on-write of pages that are otherwise shared with the parent process.
To ignore child processes, you can add --child-silent-after-fork=yes when running valgrind. Although this isn't much use if you're looking for a way of getting useful information on the child itself obviously.

[KoBeWi]

@qarmin Is this still valid in current master?

[qarmin]

For now no.
Godot 4.0 from which I know, doesn't have now PRIME detection, but adding that feature probably still will have leaks.

[KoBeWi]

For now no.

So no point in keeping this open for now.

[akien-mga]

Well I'd keep this open for 3.2, as it's valid there. And whatever fix is done for 3.2 should be applicable for master too, unless we drop platform/linuxbsd/detect_prime_x11.cpp.

[akien-mga]

Fixed by #56036.

[madmiraal]

This should be reopened, because #56036 was reverted.

[Rubonnek]

Fixed in 3.x in #69400 with commit 5ada214.
Also fixed in master in #68345.