From: Florian Weimer <fweimer@redhat.com>
To: "Paul Eggert" <eggert@cs.ucla.edu>, "Jan Synáček" <jsynacek@redhat.com>
Cc: 23760@debbugs.gnu.org
Subject: bug#23760: 25.0.95; emacs 25.0.95 doesn't build with glibc-2.23.90
Date: Mon, 20 Jun 2016 12:15:40 +0200 [thread overview]
Message-ID: <d5e4af4a-2458-54bb-0daa-9024b750cc7c@redhat.com> (raw)
In-Reply-To: <5767BFC2.3090504@cs.ucla.edu>
On 06/20/2016 12:04 PM, Paul Eggert wrote:
> On 06/20/2016 11:21 AM, Florian Weimer wrote:
>>
>> The usual mechanism for deprecation and removal of an API does not
>> work if the symbol is interposed because it will be unversioned, and
>> unversioned symbols preempt versioned symbols. As a result, even if
>> the symbol is a compat symbol, you can produce new binaries which use
>> the removed API.
>>
>
> True, but in this particular case Emacs is replacing malloc as well as
> __malloc_initialize_hook etc., so I don't see a problem. Although new
> Emacs binaries will still use the removed API, they will also support
> the removed API.
You need just one linked DSOs which somehow manages to call a function
in the glibc malloc implementation, and interesting things will happen.
> What *could* be a problem is if the new glibc malloc API supplies
> symbols that Emacs does not supply, and if other parts of the new glibc
> use these symbols. But I don't see this happening either (and if it did
> happen, poisoning __malloc_initialize_hook wouldn't fix it).
We already have this problem with malloc_usable_size, and perhaps some
of the aligned allocation functions.
This reminds me of this glibc bug, which I've put on my list to fix:
<https://sourceware.org/bugzilla/show_bug.cgi?id=17730>
I think after that, at least glibc will be interposition-clean.
> Perhaps poisoning __malloc_initialize_hook helps for some theoretical
> applications, but for Emacs I don't see how it is a win.
I'm worried that Emacs developers decide to ignore the API removal and
keep using glibc malloc and the malloc_set_state function it provides.
If we can turn the latter into a compatibility symbol during this
development cycle, that would go a long way towards addressing my concern.
Florian
next prev parent reply other threads:[~2016-06-20 10:15 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-13 10:48 bug#23760: 25.0.95; emacs 25.0.95 doesn't build with glibc-2.23.90 Jan Synáček
2016-06-13 15:58 ` Glenn Morris
2016-06-14 6:09 ` Jan Synacek
2016-06-14 6:17 ` Florian Weimer
2016-06-19 3:02 ` Paul Eggert
2016-06-20 8:48 ` Florian Weimer
2016-06-20 9:03 ` Paul Eggert
2016-06-20 9:21 ` Florian Weimer
2016-06-20 10:04 ` Paul Eggert
2016-06-20 10:15 ` Florian Weimer [this message]
2016-07-06 13:29 ` Paul Eggert
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