Function finally_stack_size 

pub fn finally_stack_size() -> usize

The current number of entries of igraph’s finally stack on the calling thread (IGRAPH_FINALLY_STACK_SIZE, undocumented in igraph_error.h).

It is zero outside of igraph calls; inside a callback it counts the temporaries of the igraph functions that are running.

assert_eq!(igraph::error::finally_stack_size(), 0);