Change in glibc's strncmp -> segfault?

Change in glibc's strncmp -> segfault?

[Bob Schmertz]

Hi,

I man page for strcmp on my Linux system, and it doesn't say anything
about the behavior of strcmp or stsrncmp when null pointers are passed. 
But sometimes you call add_match_part explicitly with NULL parameters for
the first six params.  Two of these are immediately passed into a strncmp
call.

I upgraded my glibc on my Gentoo box in the last day or two to 2.3.2-r9. 
Unfortunately, I don't know what version I had before.  From around that
time, I started getting crashes when I would tab-complete a directory
name.  I made it whole again by changing line 344 in compmatch.c
(downloaded v. 4.1.1 today) from

    if (!strncmp(l, w, wl))

to 
    if (l && !strncmp(l, w, wl))

I suppose it should really be (l && w && !strncmp(...)), on the chance
that there is somewhere that you are calling add_match_part with a null w
but a non-null l, but this fixed my immediate problem.  I have no idea if
this solution is "correct", but I hope at least I have pointed out the
right problem.

=====
Cheers,
Bob Schmertz

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Re: Change in glibc's strncmp -> segfault?

[Peter Stephenson]

Bob Schmertz wrote:
> I man page for strcmp on my Linux system, and it doesn't say anything
> about the behavior of strcmp or stsrncmp when null pointers are passed. 
> But sometimes you call add_match_part explicitly with NULL parameters for
> the first six params.  Two of these are immediately passed into a strncmp
> call.

You're right, that's weird.  I've applied your change, since it looks
like the intention is either both pointers are NULL or neither.

The author for that part of the shell went off to do some real work a
couple of years ago.

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
CSR Ltd., Science Park, Milton Road,
Cambridge, CB4 0WH, UK                          Tel: +44 (0)1223 692070


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