limits

README

Resource limits

Limits bound how much CPU and stack a script may consume, so a host can run untrusted or buggy code without a crash or an unbounded loop.

go run ./examples/limits

Expected output:

normal             completed
deep recursion     completed
busy loop          stopped: execution step limit exceeded
host still in control after all three

Key points:

• MaxCallDepth caps nested calls. Exceeding it raises a catchable RangeError ("Maximum call stack size exceeded") — a normal JS exception the script can catch and recover from (so the "deep recursion" case completes). It also keeps recursion below the point where the Go stack would overflow.
• MaxSteps caps evaluation steps (statements, loop iterations, calls). Exceeding it aborts with an uncatchable *LimitError: try/catch cannot swallow it, and control returns to the host. This guarantees a busy loop like while (true) {} terminates even without a context deadline.
• Both default sensibly (MaxCallDepth 6000, MaxSteps unlimited). Combine with WithContext(ctx) (a wall-clock deadline) and WithSecurity(...) for a fully locked-down sandbox — see the sandbox example.

Documentation

Overview

Example: resource limits for untrusted code.

Limits bound how much a script may consume so a host can run untrusted or buggy code without a crash or an unbounded loop:

• MaxCallDepth caps recursion (a catchable RangeError, as in real engines).
• MaxSteps caps evaluation steps (an UNCATCHABLE abort — try/catch cannot swallow it — so a busy loop always terminates).