Re: ping #3: [RFA] Add --with-libz-prefix option in config/zlib.m4

[Mark Wielaard <mjw@redhat.com>]

On Wed, Feb 18, 2015 at 01:54:17PM -0800, H.J. Lu wrote:
> On Wed, Feb 18, 2015 at 1:40 PM, Mark Wielaard <mjw@redhat.com> wrote:
> > On Wed, 2015-02-18 at 12:53 -0800, H.J. Lu wrote:
> >> On Wed, Feb 18, 2015 at 12:32 PM, Mark Wielaard <mjw@redhat.com> wrote:
> >> > That doesn't seem like a smart default. And why is is Linux/x86 only?
> >> > Shouldn't that be something that is done explicitly by a distro
> >> > configuring binutils after making sure it actually is beneficial
> >> > (debuginfo is often compressed in a different way, on the package/file
> >> > level or with dwz). And after making sure all tools actually work with
> >> > it? There are various tools that don't handle the .zdebug format like
> >> > valgrind. And at least elfutils has trouble with it for ET_REL files,
> >> > like kernel modules, because relocations don't actually apply anymore to
> >> > the section data as is (but only after the decompression).
> >>
> >> Now it becomes a monthly topic:
> >>
> >> https://sourceware.org/ml/binutils/2015-01/msg00089.html
> >
> > Thanks, I hadn't seen that before. Alan Modra makes some good points in
> > that thread why it is not a good change:
> > https://sourceware.org/ml/binutils/2015-01/msg00135.html
> > Do people agree with that? And/Or can the change be reverted for now
> > till there is agreement it is a desirable default?
> >
> 
> It may not be a good idea for all targets.  If you find an issue
> on Linux/x86, please file a bug binutils report.

The issue is that this is not something that is target architecture
specific. As others have pointed out this isn't something that is
target architecture-dependent. So please first get agreement on whether
or not to default for the OS (or for all ELF targets or the GNU targets).
Otherwise distros will have to revert on a target by target basis to get
something consistent. Secondly the bug is not directly in binutils (but
there might be an issue between versions compiled with/without zlib
support). If .zdebug sections are left in on disk ET_REL files, like
kernel modules, there is a problem for programs that don't deal with
.zdebug sections (and/or relocations against them) in ET_REL files
like elfutils, systemtap, debugedit, dwz, etc.

Thanks,

Mark