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288c544827
ScopeCollector::add_declaration() was adding var declarations to the top-level scope's m_var_declarations once per bound identifier and once more after the for_each_bound_identifier loop - so a `var a, b, c` would be added 4 times instead of 1. The Script constructor iterates m_var_declarations and expands each entry's bound identifiers, resulting in O(N²) work for a single var statement with N declarators. Running the Emscripten-compiled version of ScummVM with a 32,174- declarator var statement, this produced over 1 billion entries, consuming 14+ GB of RAM and blocking the event loop for 35+ seconds. After this fix, this drops down to 200 MB and just short of 200ms.
9 lines
308 B
JavaScript
9 lines
308 B
JavaScript
test("var statement with many declarators does not hang", () => {
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const count = 50000;
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const names = Array.from({ length: count }, (_, i) => `v${i}`);
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const source = `var ${names.join(",")};`;
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const start = Date.now();
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eval(source);
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expect(Date.now() - start).toBeLessThan(5000);
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});
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