Re: glibc 2.34 - Hard ABI freeze effective immediately.

[Florian Weimer <fweimer@redhat.com>]

* H. J. Lu:

> On Sun, Jul 25, 2021 at 2:55 PM Florian Weimer <fweimer@redhat.com> wrote:
>>
>> * H. J. Lu via Libc-alpha:
>>
>> > It was a mistake to export _r_debug from ld.so:
>> >
>> > https://sourceware.org/bugzilla/show_bug.cgi?id=28130
>> >
>> > I'd like to deprecate _r_debug in glibc 2.34 and replace it with:
>> >
>> > /* Return the address of that structure used by the dynamic linker.  */
>> > extern struct r_debug * __r_debug_location (void) __attribute_const__;
>> > #define _r_debug (*__r_debug_location ())
>> >
>> > so that I can extend struct r_debug for libraries loaded with dlmopen:
>> >
>> > https://gitlab.com/x86-psABIs/Linux-ABI/-/issues/2
>>
>> We need to keep it as a symbol because debuggers use it.
>
> _r_debug is only needed in the static executable.  Debuggers should use
> DT_DEBUG for dynamic executables.

We don't really know that for sure, do we?  This needs more
investigation, and we are out of time for the release.

>> changes in glibc 2.34.
>>
>> The replacement could use a separate symbol version (GLIBC_DEBUG) with
>> different ABI stability rules, which would pave the way towards
>> backporting.
>
> There is no need for a special version symbol.   I have a proposal to make
> it both forward and backward compatible.

If it's GLIBC_2.35, we won't be able to backport it.

Thanks,
Florian