Function Argument Evaluation

[Stephen Clamage]

jdp at polstra.UUCP (John Polstra) writes:

|    #include <stdio.h>
|    int x = 100, y = 200, *p;
|    main() {
|	printf("%d %d\n", *(p = &x), *(p = &y));
|    }

|Could a conforming compiler translate this in such a way that the output
|of the program is "200 200"?
|I believe it could, based on this quote from section 3.3.2.2 of the
|October 31, 1988 draft:

|    The order of evaluation of the function designator, the arguments,
|    and subexpressions within the arguments is unspecified, but there is
|    a sequence point before the actual call.

The statement is identical in the final standard, and is the reason
why your example shows a legal result.  Legal results from this
example are
200 200 with evaluation order p=&x p=&y push(*p) push(*p)
100 100 with evaluation order p=&y p=&x push(*p) push(*p)
100 200 with evaluation order p=&x push(*p) p=&y push(*p)
200 100 with evaluation order p=&y push(*p) p=&x push(*p)
-- 

Steve Clamage, TauMetric Corp, steve at taumet.com