Historically this has been
+accomplished by declaring the counter itself to be volatile, but the
+ambiguity of the C standard on the semantics of volatile make this practice
+vulnerable to overly creative interpretation by compilers.

It's even worse when accessing through a volatile casted pointer;
see for example the recent(*) GCC bugs in that area.

(*) Well, not _all_ that recent.  No one should be using the 3.x
series anymore, right?

Explicit
+casting in atomic_read() ensures consistent behavior across architectures
+and compilers.

Even modulo compiler bugs, what makes you believe that?


Segher

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