Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures

[Segher Boessenkool <segher@kernel.crashing.org>]

> Here, I should obviously admit that the semantics of *(volatile int *)&
> aren't any neater or well-defined in the _language standard_ at all. 
> The
> standard does say (verbatim) "precisely what constitutes as access to
> object of volatile-qualified type is implementation-defined", but GCC
> does help us out here by doing the right thing.

Where do you get that idea?  GCC manual, section 6.1, "When
is a Volatile Object Accessed?" doesn't say anything of the
kind.  PR33053 and some others.

> Honestly, given such confusion, and the propensity of the "volatile"
> type-qualifier keyword to be ill-defined (or at least poorly 
> understood,
> often inconsistently implemented), I'd (again) express my opinion that 
> it
> would be best to avoid its usage, given other alternatives do exist.

Yeah.  Or we can have an email thread like this every time
someone proposes a patch that uses an atomic variable ;-)


Segher