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Message-ID: <20140725104056.GO9928@port70.net>
Date: Fri, 25 Jul 2014 12:40:57 +0200
From: Szabolcs Nagy <nsz@...t70.net>
To: Jens Gustedt <jens.gustedt@...ia.fr>
Cc: musl@...ts.openwall.com
Subject: Re: C11 threads
* Jens Gustedt <jens.gustedt@...ia.fr> [2014-07-25 12:00:37 +0200]:
> after I have seen that gcc since 4.9 has a working implementation of
> atomics, I convinced myself to implement C11 threads within musl.
>
the conclusion about threads.h was that it should be
abi compatible with glibc so we are waiting for them
so i think you should coordinate with libc-alpha too
> Choices :
>
> - all types are just the corresponding POSIX types
>
if glibc does the same then it's ok
> Issues :
>
> - a lot of C11 are just weak symbols. to avoid polluting the link
> space of a C11 application, I had to transform a lot of POSIX
> function symbols into weak symbols, too.
>
i think this not ok: posix usually requires inequal
function pointers for all public functions
> - the include file threads.h includes pthread.h, so the namespace of
> the C11 implementation is poluted with the pthreads stuff
>
i think this is not ok in the final version
> - pthread_create and thrd_create are still too tightly linked
> together. It would be good to split the corresponding file in two,
> but this would make maintenance a bit more difficult.
>
> - there are still some symbols missing, for some of the functions
> that I implemented as macro. work for a winter day
>
i assume you just have to add a ptototype before the macro
definition and provide a trivial wrapper implementation
> - I don't have much tests for all of this
>
> /* Don't create just additional symbols for the simple reason that the
> return type of the POSIX and C11 functions are different. */
>
> int __pthread_once(once_flag *, void (*)(void));
> // void call_once(once_flag *flag, void (*func)(void));
> #define _call_once(FL, FU) (void)__pthread_once((FL), (FU))
> #define call_once _call_once
>
the additional symbols are necessary
and _[a-z] is not reserved for arbitrary usage for
the implementation (only for file scope identifiers)
> /* Best of all worlds, these are just weak aliases */
> int cnd_broadcast(cnd_t *); // pthread_cond_broadcast
posix is not yet aligned with c11, but i think they will
require inequal function pointers for these functions
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