svn commit: r322824 - in head: lib/clang share/mk usr.bin/clang

[John Baldwin]

On Friday, August 25, 2017 12:30:11 PM Warner Losh wrote:
> On Fri, Aug 25, 2017 at 12:27 PM, Ed Maste <emaste at freebsd.org> wrote:
> 
> > On 25 August 2017 at 14:07, Ryan Libby <rlibby at gmail.com> wrote:
> > > On Wed, Aug 23, 2017 at 4:30 PM, John Baldwin <jhb at freebsd.org> wrote:
> > >> Author: jhb
> > >> Date: Wed Aug 23 23:30:25 2017
> > >> New Revision: 322824
> > >> URL: https://svnweb.freebsd.org/changeset/base/322824
> > >>
> > >> Log:
> > >>   Improve the coverage of debug symbols for MK_DEBUG_FILES.
> > >>
> > ...
> > > This causes llvm to emit hundreds of new warnings [1] for
> > > "DWARF2 only supports one section per compilation unit"
> > >
> > > Are these expected?  Are they a concern?  Should we silence them?
> > > Is this an upstream llvm bug [2]?
> >
> > I'm not sure they were "expected" but I guess are an unsurprising
> > consequence of building more things with debug. In any case they're
> > not a concern.
> >
> > It is an llvm bug (the warning really ought not be emitted for empty
> > sections), but upstream is probably not too concerned as (most? all)
> > other platforms are not using dwarf2.
> >
> > The right answer for us is likely to just stop defaulting to dwarf2
> > (and specifying it via CFLAGS for kernel if necessary).
> >
> 
> What's the status of kicking gdb out of the tree? If we kick it out, we can
> stop doing dwarf2 and move to something more modern. Last time this issue
> came up, that was the decision, pending a few issues with the gdb port
> which I think John Baldwin is getting close to reaching closure on.

gdb is mostly disabled in-tree, but there is no in-tree replacement for the
kgdb stack trace from /usr/sbin/crashinfo if the gdb port is not installed,
and there won't be until lldb grows some kernel support.  OTOH, for most
platforms /usr/bin/gdb is now disabled (hidden in /usr/libexec) so isn't
relevant for userland binaries certainly.  The kernel probably doesn't
benefit much from DWARF > 2 (except perhaps for .dwo files if we decide to
use those at some point) as the other things added since DWARF2 are largely
about handling C++ features like r-value references, etc.

-- 
John Baldwin