Re: new cmp -i 99999999999999999999 failure

[Paul Eggert]

On 2023-06-25 12:26, Jim Meyering wrote:
> I was surprised to see your just-added "cmp" test failing, but only on Fedora 
> 38.
> This would report a difference:
>
>    echo a>a;echo b>b; src/cmp -i 99999999999999999999 a b

Hmm, it doesn't fail for me on Fedora 38 x86-64. uname -a reports:

Linux penguin.cs.ucla.edu 6.3.8-200.fc38.x86_64 #1 SMP PREEMPT_DYNAMIC 
Thu Jun 15 02:15:40 UTC 2023 x86_64 GNU/Linux

and 'dnf list glibc' says it's 2.37-4.fc38.

What file system are you using? I ran my tests on ext4, and on tmpfs, 
and they all worked without your patch installed.

What does strace say?

Is there some ulimit thing that prevents large lseeks?

A downside of the patch is that it breaks cmp on growing files due to a 
TOCTOU race. Is there some better way to work around the problem, 
whatever it is?

In trying out the patch I discovered that it sometimes called read with 
very large sizes, and fixed that with the attached. I think this bug 
happened even without the patch.

0001-cmp-do-not-try-to-read-2-64-1-bytes.patch
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