Stack overflow AFTER using stacker

help
1

so i recent had a borrow checking problem, and the (very kind) @steffahn recommended that I use the stacker crate instead of trying too manually manage a stack (to which I agree).

but then, after it was solved, I noticed that after calling stacker::maybe_grow, it exited and seemed to suggest that a stack overflow had occurred.

repo is here.

to reproduce:

git clone https://github.com/pro465/rhokell
cd rhokell
echo "exp(s s z(), s s s s s s s s s s s s z())" | cargo r ./examples/peano.rhk

output on my machine (windows 11):

    Finished dev [unoptimized + debuginfo] target(s) in 0.02s
     Running `target\debug\rhokell.exe .\examples\peano.rhk`
welcome to rhokell v0.1.0!
input `q`, `quit`, or `exit` for exiting the REPL
=> <4096*"s " + "z()">
thread 'main' has overflowed its stack
error: process didn't exit successfully: `target\debug\rhokell.exe .\examples\peano.rhk` (exit code: 0xc00000fd, STATUS_STACK_OVERFLOW)

the only problem is, i do not have any deeply recursive calls after that. in fact, the only thing that happens is it prompts the user for another expression.

2

Are you able to run your program under a debugger? If it overflows the stack, a debugger will let you see the backtrace and figure things out.

1 Like
3

Println debugging points to the dropping of expr (from let expr = rhokell::parse_expr(line);) causing the stack overflow.

4

Hereā€™s a possible fix I could come up with

impl Drop for Func {
    fn drop(&mut self) {
        stacker::maybe_grow(32 * 1024, 1024 * 1024, || {
            drop(std::mem::take(&mut self.args));
            // or maybe just `self.args.clear();` as thatā€™s shorter šŸ˜
        });
    }
}

(I donā€™t like how these magic numbers 32 * 1024, 1024 * 1024 are repeated everywhere. Maybe youā€™ll want your own wrapper function[1] to be more DRY.)

  1. For example

    fn with_stacker<R>(f: impl FnOnce() -> R) -> R {
    stacker::maybe_grow(32 * 1024, 1024 * 1024, f)
}
    ā†©ļøŽ
2 Likes
5

oh right, I completely forgot that Drop exists. I guess that's what you get for using Rust too long :joy:

6

thanks so so much! :heart:

7

i know only of gdb, and I don't think it runs on wondows? let me find out...