evaluator doesn't pass max_iterations when computing the frame base

[tromey]

If the caller sets the maximum number of iterations to allow, then when computing the frame base, this value should be passed in. Otherwise it seems that it might be possible to use this to circumvent the limiting step.

[fitzgen]

@tromey care to provide an outline of what a fix would look like and potentially mentor a new contributor? If so, I'll get this bug on This Week In Rust's "help wanted" section.

[tromey]

Currently EvaluationContext::frame_base is expected to simply return the frame base. However, computing this might require evaluating a DWARF expression. So, one way to solve the problem would be to add a new Option<u32> argument to this function, with it then returning the updated value (we'd have to provide some API to fetch it from the evaluator). Another way would be to have frame_base expose any underlying expression for direct evaluation, something the evaluator can already do.

[tromey]

This is still relevant, but now what's needed is a way to extract the number of remaining allowed operations from the evaluator, and then an additional argument to resume_with_frame_base to pass in an updated value.