Re: Upstream asks: unportable patch for mirrormagic?

[Holger Schemel <aeglos@valinor.owl.de>]

Hello Lukas,

> > > > -       gi->checked = va_arg(ap, boolean);
> > > > +       gi->checked = (boolean) va_arg(ap, int);
[...]

> Well, the patch should be correct ANSI C, I wonder how it worked on other
> architectures before. The reason is that a function with variable argument
> list gets called with an argument of type unsigned char, so this first is
> a case for "default promotion" to int. The corresponding paragraph from
> the glibc documentation:
> 
>   Since the prototype doesn't specify types for optional arguments, in a
>   call to a variadic function the default argument promotions are
>   performed on the optional argument values. This means the objects of
>   type char or short int (whether signed or not) are promoted to either
>   int or unsigned int, as appropriate; and that objects of type float are
>   promoted to type double. So, if the caller passes a char as an optional
>   argument, it is promoted to an int, and the function can access it with
>   va_arg (ap, int).

This seems to be the solution -- thanks a lot for making this clear!

Best regards,
		Holger
-- 
  // Holger Schemel        |
\X/  aeglos@valinor.owl.de | Microsoft -- confusion at your fingertips.