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

[Satyam Sharma <satyam@infradead.org>]

On Thu, 16 Aug 2007, Segher Boessenkool wrote:

> > 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?

Try a testcase (experimentally verify).

> GCC manual, section 6.1, "When
> is a Volatile Object Accessed?" doesn't say anything of the
> kind.

True, "implementation-defined" as per the C standard _is_ supposed to mean
"unspecified behaviour where each implementation documents how the choice
is made". So ok, probably GCC isn't "documenting" this
implementation-defined behaviour which it is supposed to, but can't really
fault them much for this, probably.
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