[Debian-med-packaging] Bug#982384: [Help] Bug 982384: Warnings profile count data file not found

[Andreas Tille]

Hi Helmut,

Am Mon, Dec 05, 2022 at 04:54:10PM +0100 schrieb Helmut Grohne:
> > > On 5 December 2022 12:24:23 pm IST, Andreas Tille <tille at debian.org> wrote:
> > > >Since git blames you about last changes on the lines with the option in
> > > >question could you please comment about this?
> 
> The assumption that the one who last touched this is at fault is an
> interesting one.

I make a strict distinction between "please comment" and "is at fault".
Thus my wording "please comment".

> Unfortunately, it is quite distant from the truth.
> 
> > > I simply applied patch supplied by Helmut to make build cross-buildable. Please check Bug#989942 for the explanation and context.
> 
> The next step is forwarding the question to the next person until
> someone is found who does actual research. :-/

I've learned that communication is better than just removing a suggested
patch.  The hint I've got was about removing this part of the patch.
Thus I considered it sensible to ask the author of the patch to comment
on this.
 
> > Bug #982384 (libdeflate: Warnings profile count data file not found)
> > implies that the patch you provided once is not working as expected.
> > Would you mind commenting on this issue?
> 
> I think the matter is relatively simple. You say that the
> -Wmissing-profile warnings shouldn't be there and I agree. You also
> imply that they haven't been there forever. So we're likely talking
> about a regression here, right?
> 
> Once we assume to have a regression, there is a dead simple way of
> figuring out: Just go back in the build logs and locate a version that
> doesn't contain these warning. I've done this for your convenience and
> it turns out that 1.2-1 is the last version that lacks these warnings.
> 1.3-1 is the first that contains them. The changelog for 1.3-1 is:
> 
> | libdeflate (1.3-1) unstable; urgency=medium
> |
> |   * New upstream version, now provides libdeflate-g{un,}zip in /usr/bin
> |   * debhelper-compat 12
> |   * Standards-Version: 4.4.0
> |   * Remove trailing whitespace in debian/rules
> |   * Set upstream metadata fields: Name.
> |
> |  -- Michael R. Crusoe <michael.crusoe at gmail.com>  Fri, 23 Aug 2019 12:28:07 +0200
> 
> I think this would be a better start for research than blaming random
> patches.
> 
> While we can now start blaming someone else, we should not rule out
> possible toolchain changes as a cause given that 1.2-1 and 1.3-1 are
> half a year apart and were built with gcc 8.2 and gcc 9.2 respectively.
> Quite simply, it could be that the profile guided optimization never
> worked, but only gcc 9 would start warning about it. Maybe we could
> check when that warning was added to gcc?
> 
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86957
> 
> That happens to be gcc 9. Surprise!
> 
> So while we don't have proof yet, it seems quite likely that profile
> guided optimization never worked for libdelfate. Just now, gcc tells us
> about that.
> 
> Hope this helps

Sure it helps, thanks a lot

     Andreas.

-- 
http://fam-tille.de