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Re: pthread sem_open : private glibc functions (__libc*
- From: Florian Weimer <fweimer at redhat dot com>
- To: Carlos O'Donell <carlos at redhat dot com>
- Cc: Tone Kastlunger <users dot giulietta at gmail dot com>, libc-alpha at sourceware dot org
- Date: Wed, 20 Feb 2019 09:12:46 +0100
- Subject: Re: pthread sem_open : private glibc functions (__libc*
- References: <CAHCc5YXavph5xnbq4Mvh2rwFg976DrobR7XE1Uz4FE_=6w1iBA@mail.gmail.com> <firstname.lastname@example.org>
* Carlos O'Donell:
> On 2/19/19 8:26 AM, Tone Kastlunger wrote:
>> the sem_open implementation in the pthread library seems to refer to
>> privately defined aliases of some functions of the glibc
>> (__libc_open/cloe, __libc_write for instance).
>> On the other hand, in the same implementation
>> other glibc function calls are addressed via the (usual) public counterparts
>> (for example unlink).
>> I'm puzzled about this "dissonance". Any reason behind int?
> It's complicated.
> In this case it's libpthread calling to libc for unlink and munmap.
> So it's easiest to call the public symbol because we know in the
> given standard, POSIX, which defines sem_open, we must also have
> a working unlink and munmap.
> So there is no namespace issue, and there is no PLT avoidance needed.
But that's true for open and write as well. I don't know for certain,
but I suspect it's related to the interceptors for open and write in
libpthread (which are still there today, but are not actually needed).