Bug when starting with empty varray

[nikolaushuber]

The following example program seems to illustrate a bug when starting with an empty varray:

open Varray
let t = empty ( )
push_back t '.'
pop_front t

Interestingly, the behaviour seems to depend on the particular platform this is running on. On my MacBook with M2 ARM the above program results in a segmentation fault. On my Intel MacBook it returns a character, however, it is not the one previously pushed and it also changes each time the program is run.

This was found with an upcoming feature in ortac/qcheck-stm