Snap package crashes when closing window; infinite recursion

[RavanH]

Trying to run poedit from command line in Ubuntu 18.10, I get:

$ poedit
Fontconfig warning: line 5: unknown element "its:rules"
Fontconfig warning: line 6: unknown element "its:translateRule"
Fontconfig error: line 6: invalid attribute 'translate'
Fontconfig error: line 6: invalid attribute 'selector'
Fontconfig error: line 7: invalid attribute 'xmlns:its'
Fontconfig error: line 7: invalid attribute 'version'
Fontconfig warning: line 9: unknown element "description"
Fontconfig warning: "/snap/poedit/8/gnome-platform/etc/fonts/conf.d/10-hinting-slight.conf", line 4: unknown element "its:rules"
Fontconfig warning: "/snap/poedit/8/gnome-platform/etc/fonts/conf.d/10-hinting-slight.conf", line 5: unknown element "its:translateRule"
Fontconfig error: "/snap/poedit/8/gnome-platform/etc/fonts/conf.d/10-hinting-slight.conf", line 5: invalid attribute 'translate'
Fontconfig error: "/snap/poedit/8/gnome-platform/etc/fonts/conf.d/10-hinting-slight.conf", line 5: invalid attribute 'selector'
Fontconfig error: "/snap/poedit/8/gnome-platform/etc/fonts/conf.d/10-hinting-slight.conf", line 6: invalid attribute 'xmlns:its'
Fontconfig error: "/snap/poedit/8/gnome-platform/etc/fonts/conf.d/10-hinting-slight.conf", line 6: invalid attribute 'version'

(…and so on and so on…)

Fontconfig error: "/snap/poedit/8/gnome-platform/etc/fonts/conf.d/90-synthetic.conf", line 6: invalid attribute 'version'
Fontconfig error: Cannot load default config file
Segmentatiefout (geheugendump gemaakt)

That last part is in Dutch, meaning: Segmentation error (core dump made).

[vslavik]

The errors are apparently a fontconfig mismatch. Not sure why that happens with snap's bundled content, or what crashes. @Lin-Buo-Ren does it ring a bell by any chance?

[brlin-tw]

The fontconfig errors are probably due to the incompatible fontconfig distributions shipped in the snap (from Ubuntu 16.04) and in the host (Ubuntu 18.10), as far as I know, these errors are non-fatal and shouldn't be the cause of the subsequent segmentation fault.

I can reproduce it on my end(Ubuntu 18.04), the segmentation fault occurs after I close the main window, not sure what causes it yet, though.
poedit.strace.log

[brlin-tw]

I've run the application with GDB using the --gdb option of the snap run command and attempt to get a stack trace, which appears to be an endless recursion hell:

https://gist.github.com/Lin-Buo-Ren/e0a7ea65cc2f07129a46059481ebca06

[vslavik]

@RavanH You never said: when do you get the crash, exactly?

[vslavik]

The fontconfig errors are probably due to the incompatible fontconfig distributions shipped in the snap (from Ubuntu 16.04) and in the host (Ubuntu 18.10)

It's pretty crazy that Snap doesn't have that covered (not much of isolation from the distro runtime then, is it), and FWIW wasn't present before e2721f0 — I suspect gnome-platform (889ad81) as the cause.

As for the more serious matter of the crash-on-close, that does seem like a mis-compilation. It is related to libcrypto (which is used from gnome-platform, apparently, so might be related to it too - that copy is different than the one in snap core) and boost. Something is fishy about the latter in the snap — two different versions of it are used: one as a shared library, dependency of libcpprest, the other our own newer statically built one. On one hand, that might be the cause, on the other, the crash didn't happen pre- e2721f0, but double boost was present back then.

[vslavik]

Is it possible the (entirely undocumented as far as I can tell) no-system-libraries flag is causing the libcrypto problem?

[brlin-tw]

It's pretty crazy that Snap doesn't have that covered (not much of isolation from the distro runtime then, is it)

As far as I know, the hole is explicitly opened to allow the snaps to make use the fonts installed in the host system.

Is it possible the (entirely undocumented as far as I can tell) no-system-libraries flag is causing the libcrypto problem?

As far as I know, this flag is to make Snapcraft not to automatically copying any runtime library dependencies from the build host to the snap (as most of them are shipped via the gnome-platform content snap).

This flag is no longer available in Snapcraft 3 new syntax as the feature is obsoleted if I remember correctly. If the gnome-platform snap is shipping incompatible library we might have no choice but to avoid using it.

[RavanH]

Here's the funny part: even though it sais Segfault, poEdit starts up fine in an Xorg session, but on Wayland it does crash. With the same Fontconfig messages followed by:

...
Fontconfig error: Cannot load default config file
(net.poedit.Poedit:19829): Gdk-WARNING **: 22:37:47.937: /build/gtk+3.0-2Ut_nl/gtk+3.0-3.18.9/./gdk/wayland/gdkcursor-wayland.c:169: Unable to load hand2 from the cursor theme
Segmentatiefout (geheugendump gemaakt)

Strange...

[brlin-tw]

net.poedit.Poedit:19829

Is it reproducible by running snap run poedit in a terminal?

[RavanH]

Yes, either snap run poedit or just poedit produces the same.

[vslavik]

This was indeed caused by duplicate boost libraries and is fixed in the above commit and the latest snap build (sudo snap refresh or rebooting will update to it).