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From: "goldstein.w.n at gmail dot com" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug libc/29863] Segmentation fault in memcmp-sse2.S if memory
 contents can concurrently change
Date: Tue, 13 Dec 2022 23:01:45 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D29863

--- Comment #13 from Noah Goldstein <goldstein.w.n at gmail dot com> ---
(In reply to K.S. Bhaskar from comment #12)
> While I can't speak to the other databases, the YottaDB code base goes ba=
ck
> much further than 25 years. Under the name GT.M, it first saw live
> production use in 1986. Its use of optimistic concurrency control was
> inspired by Kung & Robinson's seminal paper
> (https://www.eecs.harvard.edu/~htk/publication/1981-tods-kung-robinson.pd=
f).
> I personally know the original author of the code, as well as someone who
> has worked on the code base since the mid 1980s. In addition to those
> mentioned by Narayanan, the code has over the decades run on several other
> CPU architectures and operating systems.
>=20
> I hope this suffices as a use case.

Can you test the following dif:
```
@@ -308,7 +308,7 @@ L(ret_nonzero_vec_end_0):
  setg %dl
  leal -1(%rdx, %rdx), %eax
 #  else
- addl %edx, %eax
+ addq %rdx, %rax
  movzbl (VEC_SIZE * -1 + SIZE_OFFSET)(%rsi, %rax), %ecx
  movzbl (VEC_SIZE * -1 + SIZE_OFFSET)(%rdi, %rax), %eax
  subl %ecx, %eax

```

If that fixes things I'm okay making the change.

I'm opposed to explicitly supporting it, but am happy
to try and make this failure from the unsupported
usage less dramatic.

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