rhai/doc/src/safety/max-call-stack.md
2020-07-16 12:09:40 +08:00

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Maximum Call Stack Depth
=======================
{{#include ../links.md}}
Limit How Stack Usage by Scripts
-------------------------------
Rhai by default limits function calls to a maximum depth of 128 levels (16 levels in debug build).
This limit may be changed via the `Engine::set_max_call_levels` method.
A script exceeding the maximum call stack depth will terminate with an error result.
This check can be disabled via the [`unchecked`] feature for higher performance (but higher risks as well).
```rust
let mut engine = Engine::new();
engine.set_max_call_levels(10); // allow only up to 10 levels of function calls
engine.set_max_call_levels(0); // allow no function calls at all (max depth = zero)
```
Setting Maximum Stack Depth
--------------------------
When setting this limit, care must be also taken to the evaluation depth of each _statement_
within a function. It is entirely possible for a malicious script to embed a recursive call deep
inside a nested expression or statement block (see [maximum statement depth]).