Skip loadExtRam when the buffer is empty#74
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An empty Uint8Array is still truthy, so the constructor's `if (extRamBuffer)` guard called loadExtRam even when there was no save data to restore. For carts that don't advertise external RAM (MBC5 with EXT_RAM_SIZE_NONE, ROM-only, etc.), `_ext_ram_file_data_new` returns 0 and the wasm side then reads from a null file-data ptr inside `_emulator_read_ext_ram`. Sometimes that lands on valid wasm linear memory, sometimes it's out of bounds depending on heap state from prior alloc/free cycles — surfacing as an intermittent "RuntimeError: memory access out of bounds" in long-running embed scenarios that recreate the Emulator multiple times. Tighten the guard to also require `extRamBuffer.byteLength > 0`.
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Pull request overview
Fixes an intermittent wasm “memory access out of bounds” when creating an Emulator with an empty external-RAM restore buffer in docs/simple.js. This aligns the JS-side constructor behavior with the expectation that “no save data” should not trigger an ext-RAM load path.
Changes:
- Tighten the constructor guard to only call
loadExtRam()whenextRamBuffer.byteLength > 0.
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An empty Uint8Array is still truthy, so the constructor's
if (extRamBuffer)guard called loadExtRam even when there was no save data to restore. For carts that don't advertise external RAM (MBC5 with EXT_RAM_SIZE_NONE, ROM-only, etc.),_ext_ram_file_data_newreturns 0 and the wasm side then reads from a null file-data ptr inside_emulator_read_ext_ram. Sometimes that lands on valid wasm linear memory, sometimes it's out of bounds depending on heap state from prior alloc/free cycles — surfacing as an intermittent"RuntimeError: memory access out of bounds" in long-running embed scenarios that recreate the Emulator multiple times.
Tighten the guard to also require
extRamBuffer.byteLength > 0.