Satyam Sharma wrote:
*Unfortunately* (the trouble with C itself, is that a *committee* has made
it into ... something ... that it should not have made it into) -- anyway,
unfortunately C took it upon itself to solve a problem that it did not
have (and does not even bring about) in the first place: and the
half-hearted (or vague, call it what you will) attempt _then_ ends up
being a problem -- by making people _feel_ as if they are doing things
right, when that is probably not the case.
[ And we've not even touched the issue of whether the _same_ compiler's
implementation of volatile across archs/platforms is consistent. ]
Pardon, I was GE's representative to the original X3J11 committee, and
'volatile' was added to "codify existing practice" which is one of the
goals of a standard. The extension existed, in at least two forms, to
allow handling of memory mapped hardware. So the committee did not take
it upon itself, it was a part of the defined duty of the committee.
The intents was simple, clear, and limited, to tell the compiler that
every read of a variable in source code should result in a read, at that
point in the logic, and similar for writes. In other words, the code
should not be moved and should generate a real memory access every time.
People have tried to do many things with that limited concept since,
some with "clarification" and some with assuming the compiler knows when
to ignore volatile.
As someone noted about a committee, a committee is a poor way to get
innovation, and a good way to have a bunch of know legible people shoot
down bad ideas.
It was a fun experience, where I first learned the modern equivalent of
Occam's Razor, Plauger's "Law of least astonishment," which compiler
writers regularly violate :-(
--
Bill Davidsen <[email protected]>
"We have more to fear from the bungling of the incompetent than from
the machinations of the wicked." - from Slashdot
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