fix(string.rep): allocate proportionally to result, not repeat count#376
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fix(string.rep): allocate proportionally to result, not repeat count#376smn wants to merge 1 commit into
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`string.rep` built its result with `Enum.map_join(1..n, sep, fn _ -> str end)`, which materializes an n-element list (plus its iolist) as transient garbage. For a large repeat count that intermediate is tens of times the size of the result itself, so producing an otherwise-modest string spikes the process heap. This is what issue tv-labs#373 observes: returning a 16 MB string built by `string.rep` through `Lua.call_function!/3` left ~1 GB of reachable garbage (call_function returns before the next GC sweeps it), and on a heap-limited process the spike trips `max_heap_size` and kills it. The same spike occurs on the `Lua.eval!/2` path; it is just masked there because the surrounding decode/wrap work triggers a GC before the caller measures. Build the binary in a single pass with `:binary.copy/2` so allocation is proportional to the output. The pre-build `Limits.check_string_size!` guard is unchanged, so oversized requests still raise catchably without allocating. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01NvaxgWQcfipbKBaU4KxnuW
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Fixes #373
full disclosure: Claude helped here