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

[Paul Eggert]

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.

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