On Thu, 16 Aug 2007, Segher Boessenkool wrote:

quoted

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.