Re: CVS rtag corrupting files

[Larry Jones]

Ross Patterson writes [quoting me]:
> >
> > You mean there are four NULs at the beginning of the RCS file, just
> > before "head"?  
> 
> Yes.  And I understand your disbelief, it's astounding to me as well.

It wasn't disbelief, just making sure I understood you correctly.  I
wasn't completely sure whether you were talking about the RCS file or
the working file.

> > If so, given the way CVS creates and writes RCS files,
> > it is not possible for CVS code to be causing this problem; 
> 
> Hmm, it seems you're right - the code in rcs.c looks pretty straightforward, 
> even given the caching interactions.

That's why I wanted to be sure it was the very beginning of the RCS
file.  "head" is written as a literal string right after opening the
file, so there's no caching (or anything else) that could corrupt it.

> > it has to be
> > a bug in your C library or OS (on the server -- the client has nothing
> > to do with writing RCS files).  
> 
> That's kind of hard to believe, given that this server has lots of activity 
> and this problem *only* shows up in the CVS repository, and then only when we 
> run "cvs rtag".  My first reaction was that it was an underlying-server 
> problem, but the symptoms are very specific and they don't show up in any 
> other files.  Then again, as Holmes said, "When you have eliminated
> the impossible, whatever remains, however improbable, must be the truth."

Under what other circumstances do you read and write that many files in
such a short time?  My wild guess is that there's a subtle bug in the
kernel buffer cache, but it's just a wild guess.

> Problems?  In Linux?  Geez, next thing you'll tell me NFS is buggy too :-)

I firmly believe that *everything* is buggy.  Some bugs are just more
noticable and/or annoying than others.  :-)

-Larry Jones

He piqued my curiosity. -- Calvin