Subject: Re: c++
To: der Mouse <mouse@Rodents.Montreal.QC.CA>
From: gabriel rosenkoetter <>
List: tech-toolchain
Date: 07/01/2001 14:25:22
On Sun, Jul 01, 2001 at 02:17:46PM -0400, der Mouse wrote:
> >>> 	__asm__ ("addl %5,%1\n\tadcl %3,%0" :
> >>> 	"=r" ((USItype)( new_carry )), "=&r" ((USItype)( sum )) :
> There are two lvalues there: new_carry and sum.  Note that they are
> *output* operands from the asm.  As extend.texi says, "Output operand
> expressions must be lvalues".  (The = operand constraint character is
> not an assignment operator, though likely it was chosen for its
> similarity to one.  But output operands to extended asm statements
> function like assignment LHSes even though there is no explicit
> assignment operator present.)
> And sure enough, they're being cast.
> I think the compiler is exactly right.  What am I missing?

Um, while I certainly can't argue with that (far more
knowledgeable) explanation, then does this code work (which it
apparently does) because:

1. The cast doesn't work and we just get lucky.


2. The cast actually does work, so why worry.

If 2, then why's g++ bitching?

       ~ g r @