Re: Debug formats on Linux

[Daniel Berlin <dberlin at redhat dot com>]

dewar@gnat.com (Robert Dewar) writes:

> <<No, they have a lot of duplicate info, and there are still
> optimizations we don't pull off that we should (like factoring
> location lists and putting them in .debug_loc, factoring strings and
> putting them in .debug_str.)
> BTW, this is what -feliminate-dwarf2-dups does, is eliminate the duplicates
> Of course we still get killed by the overhead of so many labels.
> Once we have a linker we can actually eliminate dwarf2 in, dwarf2 will
> be as small as stabs, if not smaller.
> 
> It certainly has the capability to me much smaller than stabs.
> >>
> 
> Ah OK! Your definition of "proper" was pretty extensive :-)
> 
Yeah, i probably phraswed it wrong, it was late.

> Yes, indeed if all duplication is removed, things should be much better.
> It is not so easy to remove the duplicate information in the linker. Dwarf 2
> was not exactly designed to facilitate this, but it certainlyis a major need.
I know it's not, I tried for 3 weeks before i did it in the compiler.
The current linker just doesn't give us the information necessary to
do it.

I actually had a post-linker program that used libdwarf to eliminate
duplicates, but libdwarf's producer interface is too weak to make it
work well (it expects to produce one CU, and to produce it for an
object file).
--Dan