[cvsnt] cvs [2.5.03.2382] admin -s fails

[Michael Wojcik]

> From: cvsnt-bounces at cvsnt.org 
> [mailto:cvsnt-bounces at cvsnt.org] On Behalf Of David Somers
> Sent: Thursday, 20 July, 2006 08:36
> 
> I'm getting this:
> $ cvs -ttt admin -sKEWL test.c
> [snip]
> cvs admin: warning: unrecognized response `*** glibc detected 
> *** free():
> invalid pointer: 0xb77fe073 ***' from cvs server
> cvs [admin aborted]: received interrupt signal

This was discussed on the list in February of this year; see the thread
titled "Problem wit binary files after upgrading server from 2.5.01.1976
to 2.5.03.2151".

glibc is reporting an invalid free() call in the CVSNT server process.
This is a bug in the caller, which might be the CVSNT source itself or
some other library that it calls.

The pointer value glibc is displaying is misaligned, so it looks like a
bogus value being passed to free, and not a duplicate free of an
originally-valid (ie returned by malloc/calloc/realloc) pointer.

You can "work around" this problem by using an older version of glibc on
the server, or by setting MALLOC_CHECK_=0 in the server's environment to
tell glibc to silently ignore invalid free operations.  (More details
are available from all the usual suspects.)  This is a bad idea, in
general, as it merely disguises a problem that leads to undefined
behavior; but unless you can find and fix the problem  in the source you
may not have any other option.

(If I had time and a reproducible testcase, I'd track this down myself;
it'd be trivial to set MALLOC_CHECK_ to raise a signal when the invalid
free happened and then locate the offending call, and it's probably an
easy fix.  But that'd require a debug build of the current CVSNT
release, and a sufficiently new glibc, and a reliable testcase.  One of
these days I hope to have current CVSNT sources sitting around for this
sort of thing, but I don't have the time right now to set that up.)

-- 
Michael Wojcik
Principal Software Systems Developer
Micro Focus

michael.wojcik at microfocus.com
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