Re: backtrace/2224: backtrace doesn't work with bochs stub anymore

["Godmar Back" <godmar at gmail dot com>]

The following reply was made to PR backtrace/2224; it has been noted by GNATS.

From: "Godmar Back" <godmar@gmail.com>
To: "Daniel Jacobowitz" <drow@false.org>
Cc: gdb-gnats@sources.redhat.com
Subject: Re: backtrace/2224: backtrace doesn't work with bochs stub anymore
Date: Wed, 7 Feb 2007 12:36:07 -0500

 On 2/7/07, Daniel Jacobowitz <drow@false.org> wrote:
 >
 > There has been no change.  Earlier versions didn't send this particular
 > packet, which was only added recently, so did not trigger the bochs bug
 > of an incorrect reply.
 >
 > You are responding to a packet that you don't recognize.  Therefore the
 > right response is $#00, the empty packet, which informs GDB that you
 > don't recognize it.  This is described in the manual.
 >
 > If you tell GDB "something has gone wrong but we don't know what, so
 > here, have something syntactically incorrect" it is better for it to
 > stop and inform the user that something has gone wrong.  It could be
 > out of sync with the stub, which can lead to many hard to debug
 > problems - especially in new GDB versions.
 >
 > By the way, for an Enn response it doesn't currently matter what
 > error code you use - GDB doesn't interpret any of them specially.
 > That's a long standing weakness of the protocol; error behavior
 > is underspecified.
 >
 
 I'm not certain this interpretation fully explains what's going on/is
 consistent from gdb's point of view.
 
 The new version of gdb works if the error response from bochs is
 syntactically correct (specifically Eff), but doesn't "work" - doesn't
 pursue the 'm' commands for the backtrace if it's not syntactically
 correct. I did not change bochs to return +$#00 as you say I should
 response to a packet I don't recognize.
 
  - Godmar