fix(wasm): zero-initialize WASM page buffers to prevent memory corruption#12
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…tion Ghostty allocates page buffers via the wasm allocator (which calls wasm_alloc -> memory.grow). New memory pages on grow are zero on most runtimes but the cell layout depends on this being EXPLICITLY true: some cell fields are inspected before the first write, and a stray non-zero byte can corrupt the screen state in ways that surface much later (wrong colors, stuck cursor, dropped grapheme clusters). Patches/ghostty-wasm-api.patch is updated so the underlying buffer arrays are explicitly memset-to-zero at construction. Adds two TS-side regression tests that exercise the corrupted-render shape. Co-authored-by: Sauyon Lee <git@sjle.co> Inspired-by: coder#142
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Summary
Ports upstream PR #142: zero-init WASM page buffers explicitly so the Ghostty terminal does not read stale bytes from freshly-grown pages.
Changes are in two files:
patches/ghostty-wasm-api.patch— adds explicit@memset(..., 0)in the Zig-side page buffer constructors (CI /bun run build:wasmrebuilds the wasm binary).lib/terminal.test.ts— two new regression tests that exercise the previously-corrupted render shape.Attribution
Thanks to @sauyon for the original implementation.
Test plan
bun run fmt && bun run lint && bun run typecheckbun run build:wasm— rebuilt locally with Zig 0.15.2; 416 KB outputbun test— 333 tests pass (2 new regression tests), 0 failbun run build:libRisk
Low — the change is additive (zero-fill on creation). No API surface affected. Memory corruption fix; the worst-case is "harder-to-reproduce bugs reduce in frequency".