From: Sergey Vojtovich
Date: December 9 2010 9:18am
Subject: Re: bzr commit into mysql-5.1-bugteam branch (Dmitry.Shulga:3521)
 Bug#57450
List-Archive: http://lists.mysql.com/commits/126393
Message-Id: <20101209091844.GA1863@june>
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Hi Dmitry,

On Thu, Dec 09, 2010 at 11:51:16AM +0600, Dmitry Shulga wrote:
> Hi Sergey.
> 
> > Hi Dmitry,
> > 
> > let me try to explain my point and please correct me if I'm
> > wrong.
> > 
> > When I saw this patch for the first time, I realized that
> > batch_readline_init() may be called with tty, socket, unnamed
> > pipe or whatever that has no name on filesystem. Calling fstat()
> > on something that has no associated file name looks suspicious,
> > but I don't know for sure if it is permitted or not.
> All of these entities (unnamed pipe, socket etc.) have an associated file descriptor.
> fstat can be called for any object that have associated file descriptor and  it doesn't matter have that a name in file system or not.
> So, I don't see any problem at all.
> 
> > 
> > That's why I asked:
> >  What if I run "mysql > abc", or in other words what if
> >  input_fd is a tty?
> If input file descriptor refers to opened tty then when mysqld starts and opens stdin it gets access to this terminal for input. If such terminal associtated with your input source
> then all that you will be typing will be accessible as input to mysqld.
> 
>   
> > and later asked:
> >  What if I run my_fstat() on unnamed fd (e.g. tty, socket, unnamed
> >  pipe)?
> You can call fstat on any object that have a file descriptor. Any of next objects - tty, socket, unnamed pipe has a file descriptor
> so I don't see any problem at all.
Ok.

> > 
> > But there is no answer whatsoever. Ok.
> > 
> > Later I realized that this is probably a regression caused by
> > fix for BUG#41486. As far as I can see fill_buffer() returns
> > -1 on error and 0 on eof. But with fix for BUG#41486
> > intern_read_line() ignores error from fill_buffer(), unless
> > buffer->eof is set.
> > 
> > So the main question is: what benefit gives hidding a bug in
> > intern_read_line() instead of restoring original logics?
> First, I didn't know about bug 41486 when I was implementing my patch.
Ok.

> Second, when I was inspecting this source code I found a bug in handling of 
> error from read syscall. I fixed this error.
From what I can see if my_read() fails fill_buffer() returns -1 (failure)
immediately. What is the bug here?

> I don't consider that I should redesign this piece of source code. If redesign is needed
> then a separate request for redesign should be created.
Do you mean we're in agreement that we should restore original,
pre BUG#41486, logics?

Regards,
Sergey
-- 
Sergey Vojtovich <svoj@stripped>
MySQL AB, Software Engineer
Izhevsk, Russia, www.mysql.com