Re: C Interpreter and sizeof operator

In article <438cdcef.9338968@news-server>, ozbear@xxxxxxxxxxx (ozbear)
wrote:

> If one were writing a C interpreter, is there anything in the standard
> standard that requires the sizeof operator to yield the same value for
> two different variables of the same type?
>
> Let's assume that the interpreter does conform to the range values
> for, say, type int, but allocates storage for the variables based
> on their value. So, for two variables foo and bar
>
> int foo = 0; /* interpreter allocates two bytes */
> int bar = 200000000; /* interpreter allocates four bytes */
>
> Does the standard require that sizeof foo == sizeof bar thereby
> making this allocation scheme broken, unless hidden in some way?
> Or is it perfectly acceptable for the sizeof operator to different
> results?

sizeof (foo) must be equal to sizeof (bar).

memcpy (&foo, &bar, sizeof (foo)) must have exactly the same effect as a
simple assignment foo = bar. And that assignment must work, so your
interpreter must change the memory allocated to foo from 2 byte to 4
byte.

If I write a function

void f (int* p, int value) { *p = value; }

then calling

f (&foo, 2000000000)

must work. Basically, everything must worked as guaranteed by the C
Standard. As long as the interpreter makes sure that everything works as
it should, it is free to do whatever it likes.
.

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