Anthony DeRobertis wrote:
>
> Is the following legal?
>
> struct Window { /* ... */ };
> typedef Window* WindowPtr;
> struct Point { /* ... */ };
> extern short FindWindow(Point p, WindowPtr *x);
>
> void func(Point p) {
>    FindWindow(p,&Window());
> }
>
> It seems to me that it is...I think one can take the address of a
> temportary...but MrCpp (compiler) gives the error message "can't take
> address of register, bit field, constant or string."

The type of "Window()" is "Window". The type of "&Window()" is
"Window*". The type of the second parameter to FindWindow is
"WindowPtr*", or "Window**". You have a type mismatch. It looks to me
like the compiler is giving you the wrong error message. If you declare
the second parameter as WindowPtr, or Window*, then it should work.

--

Ciao,
Paul


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Anthony DeRobertis wrote:
>
> Is the following legal?
>
> struct Window { /* ... */ };
> typedef Window* WindowPtr;
> struct Point { /* ... */ };
> extern short FindWindow(Point p, WindowPtr *x);
>
> void func(Point p) {
>    FindWindow(p,&Window());
> }
>
> It seems to me that it is...I think one can take the address of a
> temportary...but MrCpp (compiler) gives the error message "can't take
> address of register, bit field, constant or string."

The operand of operator& must be an lvalue. A temporary is an rvalue.
Therefore you cannot take the address of a temporary.
However, if you really want Window rvalues to be addressable, you
can simply add

Window* operator&() { return this; }

to the Window definition.

BTW, your code shouldn't compile anyway, since the type of &Window()
would be Window*, while your function takes WindowPtr*, which is
Window**.
(Except, of course, if your Window struct contains a conversion
function to Window* ...)
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