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

["H.J. Lu" <hjl.tools@gmail.com>]

On Wed, Feb 18, 2015 at 11:17 PM, Mark Wielaard <mjw@redhat.com> wrote:
> 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).

As I said before, I don't think it will happen any time soon.

> 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

Please stop spreading your FUD about kernel modules.  If you find a problem
with kernel modules,  please open a binutils bug report.

> .zdebug sections (and/or relocations against them) in ET_REL files
> like elfutils, systemtap, debugedit, dwz, etc.

I opened a bug against elfutils:

https://bugzilla.redhat.com/show_bug.cgi?id=807053

It shouldn't be be too hard to fix.  We fixed it in readelf.

-- 
H.J.