echo $(recursive_function) SIGABRT

[oech3]

bash$ nproc(){ nproc; }
bash$ echo $(nproc) # returns 0 . Why ???
brush$ nproc(){ nproc; }
brush$ echo $(nproc)
thread 'tokio-runtime-worker' (25461) has overflowed its stack
fatal runtime error: stack overflow, aborting
fish: Job 1, 'brush' terminated by signal SIGABRT (Abort)

[reubeno]

I'm also not certain why bash wouldn't crash. I expect it to crash on stack overflow too, unless the FUNCNEST variable is set to a positive integer.

For brush we should implement support for FUNCNEST, but I'm not sure what else we would do. I wouldn't want to arbitrarily constrain script depth. Ideally it would be great to have a friendlier message but I'm not sure what is feasible to do in a standard Rust program to accomplish that.

[reubeno]

Okay, I thought about it more and this makes sense.

In bash, I'd expect the command substitution ($(nproc)) to run in a forked process. When the stack overflow hits from infinite recursion, the child process will abort and the parent process will continue.

In brush, subshells and command substitutions run in-process (by design). When the stack overflow hits, the entire shell goes down.