Why pass structs? (not struct p

[aglew at ccvaxa.UUCP]

...> Why pass structs by value?

I occasionally feel uncomfortable passing structs by value,
and receiving them as the return value of the function.

Frequently because the struct starts offsmall, 16 - 32 bits
(eg. struct RectCoord { short x, y; }), so I say "I should use
pass by value here because they structure is no bigger than an
int". But then I start adding stuff to the struct, more fields,
reference counts...

The only things that I don't feel guilty about are
    typedef struct Complex {
    	float re, im;
    } Complex;
and
    typedef LongLong {
    	unsigned hi, low;
    } LongLong;
the latter because the machine I work on has 64 bit integer instructions,
though the C compiler doesn't give you access to them.