[comp.lang.c++] sizeof in class declaration

leo@atcmp.nl (Leo Willems) (07/15/89)

This is a question regarding sizeof in a class declaration.
I use the sizeof operator inside a class declaration:

class p{
	int i;
	p p_in_p;		// this is illegal, size of p not yet known
public:
	p(){ i = sizeof(p); }	// is this legal ??

	int z;
};

This example does compile with -our- compiler. But is it legal to take the
size of an object in the objects declaration? 

Thanks.


Leo Willems			Internet: leo@atcmp.nl
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hughes@ns.network.com (Jim Hughes x1676) (07/16/89)

In article <533@atcmpe.atcmp.nl> leo@atcmp.nl (Leo  Willems) writes:
>This is a question regarding sizeof in a class declaration.
>I use the sizeof operator inside a class declaration:
>
>This example does compile with -our- compiler. But is it legal to take the
>size of an object in the objects declaration? 
>
>Leo Willems			Internet: leo@atcmp.nl

Not only is it legal, but it even works on AT&T 1.2. (Andrew, does it
work on 2.0 :-)  The following program prints the correct answer of 4.

Another way of making it work would be to define the function as
inline outside of the class definition.

Your other question about putting a p inside of p is also illegal
because it would be infinitely recursive.

//test.c
#include <stdio.h>

class p{
public:
        int i;
        p(){ i = sizeof(p); }   // is this legal ??
};

main() {
	p p1;
	printf("%p.i=%d\n",p1.i);
}

jim
hughes@network.com