TIL that the directories that `snapd` binds are just hard-coded, right in the guts of the thing

https://github.com/canonical/snapd/blob/aad0536a921429dd7759f9654ea7503fc4f6a875/cmd/snap-confine/mount-support.c#L935-L950

snapd/cmd/snap-confine/mount-support.c at aad0536a921429dd7759f9654ea7503fc4f6a875 · canonical/snapd

The snapd and snap tools enable systems to work with .snap files. - canonical/snapd

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@SnoopJ Ya know, GCC's driver does a better job of this, and it was written in, what, 1988?