Add a recursion limit to background evaluation #1878
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yannham
approved these changes
Mar 29, 2024
core/src/eval/mod.rs
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| pub fn eval_permissive(&mut self, rt: RichTerm) -> Vec<EvalError> { | ||
| /// - We support a recursion limit, to limit the number of times we recurse into | ||
| /// arrays or records. | ||
| pub fn eval_permissive(&mut self, rt: RichTerm, recursion_limit: u64) -> Vec<EvalError> { |
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Nitpick: should we use usize instead of u64? I guess in practice u16 is already amply sufficient, but you might prefer to use a word-aligned value. Using u64 sounds like we need the guarantee to have larger values than u32::MAX.
core/src/eval/mod.rs
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| @@ -966,7 +969,9 @@ impl<R: ImportResolver, C: Cache> VirtualMachine<R, C> { | |||
| attrs.pending_contracts.iter().cloned(), | |||
| t.pos, | |||
| ); | |||
| inner(slf, acc, value_with_ctr); | |||
| if let Some(r) = recursion_limit.checked_sub(1) { | |||
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nitpick: if we test at the very beginning of the function that recursion_limit > 0 (and return immediatly instead), we have to perform the check only once, instead of at each call site (using saturating sub instead of checked_sub)
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Adds a recursion limit (currently hardcoded to 128) to the background evaluator in nls. This limit applies to recursion in arrays or records, not to recursive function calls.
This might fix #1875 (it's hard to tell, as I can't reproduce it). But independent of that, it avoids a crash and preserves eval diagnostics.