Stack Overflow with Specific Optimization Levels When Running Test Cases in toml Crate

[cicilzx]

Hi, I'm not sure if it is a optimization bug of rustc.

I've noticed that when running test cases for toml crate (https://github.com/toml-rs/toml), I get a stack overflow when using certain specific optimization level (-C opt-level=0), but for other opt-level, the test cases will pass.

I am using cargo version: cargo 1.77.0-nightly (7bb7b5395 2024-01-20), the detailed discussion can be found in: toml-rs/toml#702

The developer have fixed the overflow by changing the limit value to a smaller value, but I still want to confirm why it doesn't overflow with rustc optimization turned on, but does overflow without it?

This is the fixing patch (changing the LIMIT to a smaller value):

[workingjubilee]

The developer have fixed the overflow by changing the limit value to a smaller value, but I still want to confirm why it doesn't overflow with rustc optimization turned on, but does overflow without it?

The tests in question involve a recursive case, and reducing the amount of stack memory used is a legal optimization of Rust code, as the exact amount of stack memory used is not considered part of Rust's program semantics.

What would the bug be, here?

[workingjubilee]

I am going to close this, please feel free to reopen this if you remember what the bug per se was.