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List:       fedora-devel-list
Subject:    Re: Fedora 32 System-Wide Change proposal: Build Python 3 to statically link with libpython3.8.a for
From:       Vít_Ondruch <vondruch () redhat ! com>
Date:       2019-11-15 15:20:14
Message-ID: 913d7d79-35c1-1ae9-6cf4-199d60a0f817 () redhat ! com
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Dne 15. 11. 19 v 15:51 David Malcolm napsal(a):
> On Fri, 2019-11-15 at 12:31 +0000, Daniel P. Berrangé wrote:
>> On Fri, Nov 15, 2019 at 01:23:09PM +0100, Miroslav Suchý wrote:
>>> Dne 15. 11. 19 v 10:21 Victor Stinner napsal(a):
>>>> I'm not sure if we need a Fedora change just for a compiler flag.
>>>> Again, the only drawback is that we will no longer be able to
>>>> override a symbol using LD_PRELOAD. Honestly, I never did that. I
>>>> don't see any use case for that. But I used LD_PRELOAD on the
>>>> libc multiple times to mock the system clock for example.
>>>>
>>>> If someone really needs LD_PRELOAD, it's quite easy to build a
>>>> custom Python without -fno-semantic-interposition.
>>> Mock's Nosync plugin use LD_PRELOAD:
>>> https://github.com/rpm-software-management/mock/wiki/Feature-nosync
>> IIUC mock would not be affected by this change.
>>
>> The LD_PRELOAD limitation described applies to symbols that are in
>> the libpython.so library.
>>
>> Those docs suggest mock is replacing the fsync() API in glibc with
>> its
>> LD_PRELOAD, so that should continue to work as normal.
>>
>> Regards,
>> Daniel
> Thinking aloud: does anyone ever use symbol overriding for anything
> other than glibc?
>
> What would it do to distro-wide performance if
>   -fno-semantic-interposition
> were added to the default rpm build flags, (and glibc added -fsemantic-
> interposition to override this)?
>
> Basically, change the default distro-wide to libraries opting-in to
> being able to be interposed, rather than opting-out (-fsemantic-
> interposition appears to be on by default, looking at the source for
> gcc).


+1

Because this was from the beginning my concern. Why do it just for
Python if possibly the whole distribution could benefit.


Vít


>
> Would other workloads get benefit?  How much would break?
>
> (Not that I'm volunteering to run the experiment myself)
>
> Hope this is constructive
> Dave
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