volatile (in comp.lang.c)

[Ray Dunn]

In article <2674 at geac.UUCP> daveb at geac.UUCP (David Collier-Brown) asks:
 [On the necessity of "volatile"]
>  Specifically:
>	1) what architectures currently use asynchronously-changing
>memory locations for program notification of events? DEC Vax,
>various CDC boxes, MIPS(tm),...

The asking of this question is a clear example of the distorted view many
people have, whose environment is restricted to DEC, SUN, CDC, IBM etc
*standard* machines.  This is not meant as a flame, only as an observation.

The answer to the question is "as many architectures as there are
proprietary designs of micro-processor based equipment which use
asynchronously changing memory locations, including *all*, for example,
which use memory mapped I/O.

As I said in an earlier posting (on reflection not very succinctly), a
compiler for a particular [micro-processor] CPU can make *no* assumptions
about the architecture that the compiled code is running on, other than [the
architecture of the microprocessor itself].

Writing a compiler for a 68000 is a different exercise than writing one for
a VAX, which is a fully defined environment.

So it's not reasonable to make these controls [e.g. "volatile"] a compiler
specific thing.

They *have* to be part of the language.

-- 
Ray Dunn.                      |   UUCP: ..!{philabs, mnetor}!micomvax!ray
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