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Re: Fedora 14 debug proposal
- From: Tom Tromey <tromey at redhat dot com>
- To: Roland McGrath <roland at redhat dot com>
- Cc: Project Archer <archer at sourceware dot org>, Jakub Jelinek <jakub at redhat dot com>
- Date: Tue, 15 Jun 2010 13:45:53 -0600
- Subject: Re: Fedora 14 debug proposal
- References: <firstname.lastname@example.org><20100613104010.6D1174077C@magilla.sf.frob.com>
- Reply-to: Tom Tromey <tromey at redhat dot com>
>>>>> "Roland" == Roland McGrath <email@example.com> writes:
Roland> For Fedora purposes, dropping .debug_pub* sections could just as
Roland> well be done in the stripping stage. And, I don't think they
Roland> really cost much space in the grand scheme of things. So there
Roland> is little real motivation to fiddle gcc at all until after we
Roland> have completed basically everything else in the related realms.
Doing it in gcc can save some space, by not putting useless stuff into
the string table. I didn't try to measure this. Just stripping the
sections does not save much space, as you hypothesized; I did a test
with objcopy on all the debuginfo I have currently installed (OO.o plus
other random bits):
opsy. du -s debug stripped
The indices are about 3x the size of the savings:
opsy. du -s Out
Tom> 3. If we are shipping GCC 4.5 in F14, I think we should enable the
Tom> .debug_types stuff by default. This will shrink debuginfo and it
Tom> makes gdb use less memory.
Roland> libdw does not yet handle .debug_types. It of course will, but
Roland> I wouldn't like to have a gcc defaults change on any queue until
Roland> we are quite concrete with getting all the support in line.
Yeah, that would be good for us too; some of the recent gcc changes
caught us by surprise. OTOH I don't want to stop Jakub's gusto, maybe
just get a little more warning of coming gdb-impacting changes.
Tom> This one is optional, in particular I assume it will be subsumed by
Tom> the other DWARF compression work.
Roland> It should be, yes. I don't see any reason that .debug_types and
Roland> DW_FORM_ref_sig8 need to survive final linking. The normal reference
Roland> forms are more efficient for consumers to use.
Why is that? I looked at the gdb code here and nothing really stood out.