DWARF5 and .gdb_index/.debug_names

David Blaikie dblaikie@gmail.com
Tue Sep 1 18:53:40 GMT 2020


On Tue, Sep 1, 2020 at 11:38 AM Tom Tromey <tom@tromey.com> wrote:

> >>>>> "Mark" == Mark Wielaard <mark@klomp.org> writes:
>
> Mark> During the BoF Pedro mentioned that the GDB DWARF5 .debug_names
> support
> Mark> is incomplete/wrong. I was wondering whether there was a good
> Mark> description of the issue and/or a bug report for it.
>
> It's been a while but last time I looked I thought gdb's process emitted
> incorrect names.  I filed this bug, with analysis:
>
> https://sourceware.org/bugzilla/show_bug.cgi?id=24820
>
> gdb's reader probably also needs updating, since it relies on this same
> incorrect reading of the standard.
>
> Having gdb write the index is mildly bad anyway.  It should be in the
> linker, and/or dwz or debuginfod.  Putting it in gdb back in the
> .gdb_index days was a mistake.
>

FWIW, there are times where you might not want to add this at production
time - at least with lld, for instance, it takes significantly more
memory/linker time. So if you're building more often than you're debugging,
it might be nice to build without an index to speed up the build/test loop,
then only pay the index building cost when you end up wanting to debug
something.

- Dave


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