fix(libc): avoid undefined memcpy in js_worker_postMessage with len==0#1483
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andreasrosdal wants to merge 1 commit into
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fix(libc): avoid undefined memcpy in js_worker_postMessage with len==0#1483andreasrosdal wants to merge 1 commit into
andreasrosdal wants to merge 1 commit into
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memcpy(dst, src, 0) is UB per C11 7.21.1 when either pointer is NULL, even if no bytes are copied — UBSan with -fsanitize=nonnull-attribute flags it and a strict optimiser may exploit the implied non-NULL attribute to elide subsequent NULL checks. In practice JS_WriteObject2 always emits a non-empty buffer, but make the call site safe by hand so the worker pipe is robust to any future serializer change. No test: triggering the UB requires data_len == 0 and malloc(0) returning non-NULL, which doesn't happen on the current writer. UBSan in CI would catch a regression.
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memcpy(dst, src, 0) is UB per C11 7.21.1 when either pointer is NULL, even if no bytes are copied — UBSan with -fsanitize=nonnull-attribute flags it and a strict optimiser may exploit the implied non-NULL attribute to elide subsequent NULL checks.
In practice JS_WriteObject2 always emits a non-empty buffer, but make the call site safe by hand so the worker pipe is robust to any future serializer change.
No test: triggering the UB requires data_len == 0 and malloc(0) returning non-NULL, which doesn't happen on the current writer. UBSan in CI would catch a regression.