observability
Alan J Rosenthal
flaps at dgp.toronto.edu
Thu Sep 7 08:33:49 AEST 1989
bvs at light.uucp (Bakul Shah) writes:
>I have some questions about `observable behavior'. How does this
>concept interact with `volatile' variables? with debuggers? with
>shared memory?
Debuggers and shared memory are not specified in the ansi C standard.
That is, there does not exist behaviour of debuggers or of shared memory
that violate the standard.
Many people claim that "volatile" is meaningless since it is not observable.
>Is a program with *no* output of any kind observable?
Yes, you can observe that it produced no output, a different observation from
observing it producing some output. However, the ansi C standard probably
doesn't prevent "int main() { return(0); }" from outputting, as a concession to
verbose environments. So there might not exist standard-violating behaviour
for the execution of a program which produces no output.
ajr
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