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From: Elena Zannoni <ezannoni@redhat.com>
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Date: Wed, 27 Mar 2002 13:31:00 -0000
To: Andreas Schwab <schwab@suse.de>
Cc: Elena Zannoni <ezannoni@redhat.com>, Andrew Cagney <ac131313@cygnus.com>,
        Jason Molenda <jason-swarelist@molenda.com>,
        gdb-patches@sources.redhat.com
Subject: Re: Minor off-by-one error in command_line_handler
In-Reply-To: <jelmcdlrbm.fsf@sykes.suse.de>
References: <20020327000106.A24311@molenda.com>
	<3CA1F421.6010009@cygnus.com>
	<15522.2853.891361.517767@localhost.redhat.com>
	<jelmcdlrbm.fsf@sykes.suse.de>
X-SW-Source: 2002-03/txt/msg00551.txt.bz2

Andreas Schwab writes:
 > Elena Zannoni <ezannoni@redhat.com> writes:
 >=20
 > |> Andrew Cagney writes:
 > |>  > > 2002-03-26  Jason Molenda  (jason-cl@molenda.com)
 > |>  > >=20
 > |>  > > 	* event-top.c (command_line_handler): Don't check penultimate
 > |>  > > 	byte in zero-length strings.
 > |>  > >=20
 > |>  > >=20
 > |>  > Yes, and thanks.
 > |>  >=20
 > |>  > Andrew
 > |>  >=20
 > |>  >=20
 > |>=20
 > |> Wait.  This is fine, but, as the comments indicate, the code was taken
 > |> from the function command_line_input in top.c, which has the same bug:
 > |>=20
 > |>       p1 =3D rl;
 > |>       /* Copy line.  Don't copy null at end.  (Leaves line alone
 > |>          if this was just a newline)  */
 > |>       while (*p1)
 > |> 	*p++ =3D *p1++;
 > |>=20
 > |>       xfree (rl);		/* Allocated in readline.  */
 > |>=20
 > |>       if (p =3D=3D linebuffer || *(p - 1) !=3D '\\')
 > |> 	break;
 >=20
 > Why?  This one looks ok.

Oh, You mean because the second part of the 'or' won't be evaluated if=20
p=3D=3Dlinebuffer (which implies that the line was empty)?

Wonder if this gives an error if run under valgrind (use the --noasync
switch).=20

Looking at the logs, the error in event-top.c came in because that
first part of the OR was deleted.

 >=20
 > Btw., command_line_handler has this:
 >=20
 >=20
 >   if (*(p - 1) =3D=3D '\\')
 >     {
 >       p--;			/* Put on top of '\'.  */
 >=20
 >       if (*p =3D=3D '\\')
 >=20
 > The condition in the last line is always true.
 >=20

Yes, thanks for catching this. Would you like to submit a fix?

Elena


 > Andreas.
 >=20
 > --=20
 > Andreas Schwab, SuSE Labs, schwab@suse.de
 > SuSE GmbH, Deutschherrnstr. 15-19, D-90429 N=FCrnberg
 > Key fingerprint =3D 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
 > "And now for something completely different."