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christianaurichzmchristianaurichzm
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test: zero-fill buffers before the string length limit check
The test allocates a buffer one byte longer than MAX_STRING_LENGTH and expects toString('utf8') to throw ERR_STRING_TOO_LONG. MAX_STRING_LENGTH counts UTF-16 units rather than bytes, so that only holds if every byte decodes to a single unit. For the two Buffer.allocUnsafe variants the contents are whatever the allocator hands back, and a single multi-byte UTF-8 sequence anywhere in the buffer decodes to fewer units than it occupies bytes, bringing the result down to MAX_STRING_LENGTH or less so that nothing is thrown. This goes unnoticed when the allocator returns zeroed pages, which is why the test passes elsewhere. The AIX builders expose non-zero contents and fail with "Missing expected exception (Error)". Refs: nodejs/reliability#1649
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‎test/parallel/test-buffer-tostring-rangeerror.js‎

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@@ -34,6 +34,12 @@ function test(getBuffer) {
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return;
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}
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}
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// MAX_STRING_LENGTH counts UTF-16 units, not bytes. Uninitialized memory can
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// hold multi-byte UTF-8 sequences, which decode to fewer units than they
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// occupy bytes, and a single one of them is enough to bring the result down
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// to MAX_STRING_LENGTH or less. ASCII bytes keep the decoded length equal to
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// the buffer length.
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buf.fill(0);
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assert.throws(() => { buf.toString('utf8'); }, message);
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}
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