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Previously, visitMemoryGrow checked `max > initial` and emitted `wasm2js_trap()` when false. This incorrectly dropped the delta expression's side effects and caused memory.grow to trap at runtime, which is invalid WebAssembly semantics. WebAssembly memory.grow never traps. Unconditionally emit the WASM_MEMORY_GROW call in visitMemoryGrow, and add needsMemoryGrow to emit the __wasm_memory_grow helper when memory.grow is used in the module or when growable memory is imported or exported. Also, when memory.grow fails at runtime (for example when exceeding declared memory maximum or passing invalid delta operands), return -1 instead of the previous memory size. Also ensure growing by 0 pages succeeds and returns the previous memory size without reallocating the buffer.
tlively
requested review from
aheejin and
stevenfontanella
and removed request for
a team
October 6, 2026 23:39
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Previously, visitMemoryGrow checked
max > initialand emittedwasm2js_trap()when false. This incorrectly dropped the delta expression's side effects and
caused memory.grow to trap at runtime, which is invalid WebAssembly semantics.
WebAssembly memory.grow never traps.
Unconditionally emit the WASM_MEMORY_GROW call in visitMemoryGrow, and add
needsMemoryGrow to emit the __wasm_memory_grow helper when memory.grow is used
in the module or when growable memory is imported or exported.
Also, when memory.grow fails at runtime (for example when exceeding declared
memory maximum or passing invalid delta operands), return -1 instead of the
previous memory size. Also ensure growing by 0 pages succeeds and returns the
previous memory size without reallocating the buffer.