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bug#21513: (now an infinite loop in grep/tests/triple-backref?)

From: Paul Eggert
Subject: bug#21513: (now an infinite loop in grep/tests/triple-backref?)
Date: Mon, 20 Jan 2020 09:50:23 -0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1

On 1/20/20 2:49 AM, Martin Liška wrote:

In this case an infinite loop is highly undesirable.

Sure, but the regex code is littered with highly undesirable code like this, as it's easy to use a weird regexp to make the code explode exponentially and there's little practical difference between that an infinite loop.

Come to think of it, the grep test infrastructure already has a way to deal with this sort of thing, so all we need to do to fix this particular glitch is adjust triple-backref to use timeout, which I did by installing the attached patch.

Thanks Andreas for diagnosing the problem. I hope there's a gcc bug report about it somewhere. I could not use Martin's recipe on Fedora 31 x86-64 because gcc -m32 -flto didn't look inside the .a files that the grep build procedure creates and uses. I've never had much luck with -flto anyway as it has a habit of running into compiler bugs. I now also see that Red Hat has qualms about the GOLD linker <https://fedoraproject.org/wiki/Changes/BINUTILS_GOLD> which the recipe relies on, as Google has decided not to continue GOLD development (which was news to me).

I'll mark Bug#21513 as done again, since the original report is fixed. The triple-backref bug is Bug#22793 and also glibc bug 11053, both of which are still open.

Attachment: 0001-tests-work-around-GCC-fprofile-generate-bug.patch
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