[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

bug#55212: GNU Linux "sort -g" can hang indefinitely when run on standar

From: Pádraig Brady
Subject: bug#55212: GNU Linux "sort -g" can hang indefinitely when run on standard input if NaNs are involved
Date: Mon, 2 May 2022 14:31:23 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:97.0) Gecko/20100101 Thunderbird/97.0

On 02/05/2022 07:03, Paul Eggert wrote:
Thanks for the bug report. This bug is entertaining, as it comes from
GCC now being so smart that it optimizes away a memset that cleared
padding bits. We added the memset in coreutils 8.14 (2011) to try to fix
the sort -g infinite loop bug (introduced in 1999), but the memset isn't
guaranteed to fix the bug because the memset can be optimized away.

If the padding bits happen to be clear already sort is OK, but if not
the results can be inconsistent when you compare two NaNs to each other,
and inconsistent results can make sort infloop.

The C standard allows this level of intelligence in the compiler, so
it's a bug in GNU 'sort'.

I installed the attached patch; please give it a try. For now I'll
boldly close the bug report; we can easily reopen it if this patch
doesn't actually fix the problem.

This is a bit slower of course, but since an edge case not a big concern:

  $ time yes nan | head -n128095 | timeout 10 sort -g >/dev/null
  real  0m0.693s

  $ time yes nan | head -n128095 | timeout 10 src/sort -g >/dev/null
  real  0m0.924s

I'll add the test case I think (attached)
since the existing one didn't trigger this.


Attachment: sort-nan-inf-adjustments.patch
Description: Text Data

reply via email to

[Prev in Thread] Current Thread [Next in Thread]