Re: C++ debugging progress

[Dan Mosedale <dmose at mozilla dot org>]

Daniel Berlin wrote:

> Subject:
>
> Re: C++ debugging progress
> From:
>
> Daniel Berlin <dan@cgsoftware.com>
> Date:
>
> Wed, 28 Nov 2001 02:43:43 -0500 (EST)
>
> To:
>
> Daniel Jacobowitz <drow@mvista.com>
> CC:
>
> <libstdc++@gcc.gnu.org>, <gdb@sources.redhat.com>
>
>
>
>On Wed, 28 Nov 2001, Daniel Jacobowitz wrote:
>
>>> For the curious, I've gotten all but two of the virtual function tests to
>>> pass in virtfuncs.exp.  I'm not entirely sure what's wrong with one of the
>>> others, and the other goes up as far as the parser (pEe->D::fd() yields
>>> "attempt to take address of value not in memory").  There's also a bunch of
>>> namespace problems, of course.
>>>
>>> I'll not be posting the patches for another day or two.  The way I do it now
>>> is grossly inefficient; I look through RTTI at every lookup instead of once
>>> per type.  It also depends on presence of RTTI.  There's not much I can do
>>> about that - or rather, I could, but AFAICT it would require walking the
>>> inheritance graph in the proper order and I don't have the machinery to do
>>> that easily.  I'm not heartbroken that we need RTTI for debugging though.
>>
>
>Nor am I.
>However:
>     * To: gdb-patches at sources dot redhat dot com
>     * Subject: Re: Using typeinfo functions to determine RTTI
>     * From: Tom Tromey <tromey at cygnus dot com>
>     * Date: 03 May 2000 09:41:50 -0600
>     * Newsgroups: cygnus.patches.gdb
>     * Organization: Cygnus Solutions
>     * References:
><Pine.LNX.4.10.10005020923450.14281-100000@propylaea.anduin.com>
><npu2ggf8g3.fsf@zwingli.cygnus.com>
>     * Reply-To: tromey at cygnus dot com
> (This was me):
> >> Does anyone mind if i use the typeinfo name, rather than
> >> the virtual table name, to figure out th real type of an object? It
> >> only matters if someone does -fno-rtti, i believe. But I have no
> >> idea how many people actually use that flag to save time/space in
> >> debugging executables.
>
> Jim> Almost all of Cygnus's customers use GDB to debug embedded apps,
> Jim> and space is often an issue there.  But I don't actually know how
> Jim> many of them use -fno-rtti.
>
> All Java programs are compiled with -fno-rtti.  This includes the C++
> component.  So presumably if this change is made it will make it even
> harder for me to debug libgcj.
>
This would also be unfortunate for Mozilla, which compiles -fno-rtti. 
 Debugging Mozilla using gdb is already extremely memory intensive, and 
being required to use RTTI would make it even worse.  :-/

Dan