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Date: Thu, 13 Apr 2006 08:10:00 -0000
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From: Eli Zaretskii <eliz@gnu.org>
To: Vladimir Prus <ghost@cs.msu.su>
CC: gdb@sources.redhat.com
In-reply-to: <e1kt1v$ssc$1@sea.gmane.org> (message from Vladimir Prus on Thu, 	13 Apr 2006 11:02:23 +0400)
Subject: Re: printfs output in wrong order in MI
Reply-to: Eli Zaretskii <eliz@gnu.org>
References: <e1j893$lse$1@sea.gmane.org> <e1kt1v$ssc$1@sea.gmane.org>
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> From:  Vladimir Prus <ghost@cs.msu.su>
> Date:  Thu, 13 Apr 2006 11:02:23 +0400
> 
> Vladimir Prus wrote:
> 
> > 
> > Hi,
> > I'm seing strange behaviour of the "printf" command if used in MI:
> > 
> >     (gdb)
> >     print &i
> >     &"print &i\n"
> >     ~"$1 = (int *) 0xbfc5f484\n"
> >     ^done
> >     (gdb)
> >     printf "%x", &i
> >     &"printf \"%x\", &i\n"
> >     ^done
> >     (gdb)
> >     ~"bfc5f484"
> >     -interpreter-exec console "printf \"%x\", &i"
> >     ^done
> >     (gdb)
> >     ~"bfc5f484"
> > 
> > The output of 'print' appears before "^done", but the output of "printf"
> > appears *after* both "^done", and the prompt, which makes it impossible to
> > reliably catch the output.
> ....
> > Any ideas why "printf" is so special?
> 
> I turns out that using 
> 
>   printf "%x\n", &i
> 
> (that is, adding "\n"), fixes the problem. Still looks like a bug to me,
> though.

I think it's expected behavior: printf uses buffered output, so if you
don't finish the line with a newline, the buffer is not flushed.
Similar ``bugs'' can be seen in any C program that displays characters
via printf without \n or fflush.