Re: Petr Sorfa's Dwarf 2 changes

[John Wolfe <jlw at caldera dot com>]

> From: Daniel Jacobowitz <drow@mvista.com>
> To: Jim Blandy <jimb@redhat.com>, John Wolfe <jlw@caldera.com>
> Cc: Andrew Cagney <ac131313@redhat.com>, gdb@sources.redhat.com
> Subject: Re: Petr Sorfa's Dwarf 2 changes
> Message-ID: <20021104202641.GA7194@nevyn.them.org>
> Mail-Followup-To: Jim Blandy <jimb@redhat.com>,
	John Wolfe <jlw@caldera.com>, Andrew Cagney <ac131313@redhat.com>,
	gdb@sources.redhat.com
> References: <200210231720.g9NHKqO32140@zenia.red-bean.com> 
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> On Mon, Nov 04, 2002 at 03:06:21PM -0500, Jim Blandy wrote:
> > 
> > Andrew Cagney <ac131313@redhat.com> writes:
> > > > I'm undertaking some related work in dwarf2read.c which will almost
> > > > certainly conflict with Caldera's changes, and I'd like to see where
> > > > you guys ended up.
> > > 
> > > Care to expand?
> > 
> > Sure --- I'm trying to put together a patch to support
> > inter-compilation unit die references, which is (the hardest?) part of
> > supporting Dwarf 2 compression.
> > 
> > I think the changes are going to be pretty widespread.
> > 
> > At the moment, dwarf2read.c has a number of global variables that
> > describe per-compilation-unit things.  These get set as we do the
> > psymtab scan, stashed in each psymtab we create, and then restored
> > each time we convert a psymtab to a symtab.  If we're going to handle
> > inter-CU references, we're going to be dealing with more than one CU
> > at a time, so that's not going to be sufficient any more --- which CU
> > you need depends on which die you're looking at.
> > 
> > I'd like to change GDB to have a per-objfile Dwarf-specific structure
> > (like struct dbx_symfile_info for STABS), and per-CU Dwarf-specific
> > structures.  These would be passed as arguments amongst the
> > dwarf2read.c functions as appropriate.  Furthermore, each die might
> > need to have a pointer to the CU that owns it.
> > 
> > Those are pretty pervasive changes, but I think the folks who have
> > worked in dwarf2read.c will agree that they're the right way to go.
> > When I've gotten something working on the branch I'll have more
> > perspective on what's really needed.
> 
> Not only will they agree, I believe Petr and John had already finished
> doing this.  Doubtless there's still some room for improvement, but the
> functionality is there...  John, do you have that merged dwarf2read
> available?
> 
> [For instance, from Petr's July posting:
>         * dwarf2read.c (build_die_ref): New function that builds
>           a new die reference if necessary, will search across
>           multiple comp units to find the reference.
>           (find_die_ref): New function that searches for a die
>           reference for a given comp unit.
>           (find_cu_header_from_begin_offset): New function that
>           searches through a link list of comp unit headers for
>           a comp unit that matches the given offset.
>  ]

Apologies for the delay in responding.  I actually took a couple of days
off.

Yes, I do.  I sent a full  copy of dwarf2read.c directly to Jim with a
copy to gdb@sources.redhat.com.  Jim got his copy, but the copy to 
gdb@sources.redhat.com was bounced to to an e-mail size limit.

The key thing is that Jim got the copy to look at.