[Python-Dev] Last-minute request: please backport bpo-33329 fix to 3.4 and 3.5

[Joni Orponen]

On Sun, Mar 10, 2019 at 7:50 AM Larry Hastings <larry at hastings.org> wrote:

> On 3/4/19 2:29 AM, Joni Orponen wrote:
>
> On Sat, Mar 2, 2019 at 7:08 AM Larry Hastings <larry at hastings.org> wrote:
>
>> This bug in bpo-33329:
>>
>> https://bugs.python.org/issue33329
>>
>>
>> This is also potentially affecting PGO builds of 2.7 on Debian Buster
> with GCC. Somehow building with Clang is fine.
>
> Does the configure time choice of compiler make a difference here for 3.4
> and 3.5?
>
> I don't know.  I only build with the default compiler on my machine, gcc.
> (My machine is Linux, 64-bit.)  It'd be swell if you tried the RCs with
> clang!
>
> */arry*
>
I've only risen this as a newer glibc was implicated as a potential source
of trouble, I have a lab / 'canary in a coal mine' server on a prerelease
OS version (Debian Buster is currently in feature freeze ~ release
candidate stage) and I've not noticed anything to have happened with a
newer glibc in relation to building Python, but I've not had success
building a PGO build of 2.7.15 with the GCC shipped at that time, but
building with Clang working fine.

I'd thus be inclined to point at digging up relevant changes in GCC than in
glibc. Currently 2.7.16 compiles just fine for me on both GCC and Clang.
2.7.15 still does not compile fine for me on GCC.

FWIW - both Python 3 RCs from above successfully complete a PGO build for
me (and thus implicitly also pass the regression tests) with Clang. They
both get stuck with GCC.

$ cat /etc/debian_version
buster/sid

$ aptitude show base-files
Package: base-files
Version: 10.1
Essential: yes
State: installed

$ aptitude show libc6
Package: libc6
Version: 2.28-8
State: installed

$ aptitude show clang
Package: clang
Version: 1:7.0-47
State: installed

$ clang --version
clang version 7.0.1-8 (tags/RELEASE_701/final)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin

$ aptitude show gcc
Package: gcc
Version: 4:8.3.0-1
State: installed

$ gcc --version
gcc (Debian 8.3.0-2) 8.3.0

And for anyone wishing to try such things out for themselves, one can
simply set the CC environment variable for the autotools provided
./configure script.

See ./configure --help for any further details and instructions.

-- 
Joni Orponen
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