Date: Mon, 18 May 2015 12:19:34 +0200 From: Szabolcs Nagy <nsz@...t70.net> To: musl@...ts.openwall.com Subject: Re: Deduplicating atomics written in terms of CAS * Jens Gustedt <jens.gustedt@...ia.fr> [2015-05-18 00:23:07 +0200]: > > The advantage of C11's model for atomic is that this a qualifier, and > then the compiler automatically checks (or ensures) that all accesses > are atomic. We don't have that luxury, here, but we could get a bit > closer to it. > the qualifierness of atomic is a bit confusing differently qualified types had the same alignment and representation so far and in some cases pointers to differently qualified types are implicitly convertible (eg assigning char* to const char* is ok). atomic is special: when the standard says 'qualified or unqualified type' it does not include _Atomic even though it is called a qualifier. (atomic is always mentioned explicitly, it can have different representation and alignment to allow implementation with locks and thus the pointers cannot be convertible) annotating everything with _Atomic in musl is problematic because the atomic bits are publicly visible in pthread types (we could use _Atomic only when building musl, but i think its usefulness should be demonstrated with examples etc before doing something that ugly.. having a_load_relaxed without typesystem help does not sound very useful)
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