[PATCH] Turn ___brk_addr into a compat symbol

[Florian Weimer]

* Adhemerval Zanella via Libc-alpha:

> On 19/11/2020 08:34, Florian Weimer wrote:
>> * Andreas Schwab:
>> 
>>> GCC hasn't been requiring the ___brk_addr symbol since 3.1, and before
>>> that only on i386 at least since 2.95.
>> 
>> GCC 2.7.2.3 uses it as well on i386.
>> 
>> I think turning it into a compatibility symbol will prevent users from
>> using these compilers to link new binaries.
>> 
>
> Is this really a wide deployed scenario?

Widely deployed is relative, especially in a glibc context with its
long list of supported targets.

> And do we really care for that awkward combination (a 20 years old
> compiler using an update runtime)?

GCC 2.7.2.3 is a bit of an outlier because the old Debian binaries
didn't run anymore because of a regression introduced in 1998 that was
only fixed last year.

For GCC 2.95, I have seen users building new programs with it quite
recently (although only reproducers for bugs in new glibc versions).

These early GCC versions have different C++ ABIs and accept language
constructs rejected by current compilers.  GCC 2.95 has been really
solid, so I guess those factors conspire to keep it around.