[COMMITTED] Remove useless comment from sysdeps/sparc/sparc32/dl-machine.h

[David Miller]

From: Zack Weinberg <zackw@panix.com>
Date: Mon, 22 May 2017 16:11:42 -0400

> On Mon, May 22, 2017 at 3:47 PM, Siddhesh Poyarekar
> <siddhesh@sourceware.org> wrote:
>> -      /* XXX The following is wrong!  Dave Miller rejected to implement it
>> -        correctly.  If this causes problems shoot *him*!  */
> 
> You got me curious, so I did some archaeology.  This comment was
> introduced in 1999, and unfortunately Drepper seems to have been in
> the habit of copying changes out of what I assume was a Cygnus Inc
> internal CVS repository in large batches, so the commit message is
> unhelpful, but the original patch to this file
> (https://sourceware.org/git/?p=glibc.git;a=blobdiff;f=sysdeps/sparc/sparc32/dl-machine.h;h=8750791fe0cf20f55250ad4c2147ebb992cadb93;hp=e6debe05ac511232cad7856be66298359f32e7b4;hb=63ae7b6309964400c6289d9030c7d336a33b304f;hpb=b4cbd37109d882aa052e7973684774eaa887071b)
> was
> 
> --- a/sysdeps/sparc/sparc32/dl-machine.h
> +++ b/sysdeps/sparc/sparc32/dl-machine.h
> @@ -56,7 +56,9 @@ elf_machine_matches_host (Elf32_Half e_machine)
>        weak_extern (_dl_hwcap_mask);
> 
>        hwcap = WEAKADDR(_dl_hwcap);
> -      return hwcap && (*hwcap & _dl_hwcap_mask & HWCAP_SPARC_V9);
> +      /* XXX The following is wrong!  Dave Miller rejected to implement it
> +        correctly.  If this causes problems shoot *him*!  */
> +      return hwcap == NULL || (*hwcap & _dl_hwcap_mask & HWCAP_SPARC_V9);
>      }
>    else
>      return 0;
> 
> and, if I'm reading the ChangeLog correctly, the true author was Jakub
> Jelinek, who I've cc:ed just on the offchance he remembers what was
> going on.
> 
> Note that this changes the sense of the test from "the hwcap is
> available AND the flag HWCAP_SPARC_V9 is set" to "the hwcap is NOT
> available OR the flag HWCAP_SPARC_V9 is set".  I do not know for sure,
> but what this smells like to me is there may have been a bunch of
> SPARCv9 binaries that were generated before hwcaps were introduced, so
> they stopped working when ld.so started paying attention to hwcaps, so
> Miller wanted to relax the rules and Jelinek didn't like that.

The context is that Drepper didn't like the change, Jakub and I were
all for it.

> What's in the file *now* appears to have reverted to the old logic
> (and that happened in 2003), so if my nose is correct, then the
> comment is indeed completely obsolete.

Even more reason to remove the stale comment.