Re: module level flags

[Zack Weinberg <zack@codesourcery.com>]

On Sat, Sep 28, 2002 at 05:00:34PM -0700, Bruce Korb wrote:
> Zack Weinberg wrote:
> > 
> > On Sat, Sep 28, 2002 at 04:46:21PM -0700, Bruce Korb wrote:
> 
> > If you've found an optimizer bug in 3.[12] not present in 3.0 and
> > prior, you could have the courtesy to *tell us what it is* so we can
> > *fix* it.
> 
> OK:  :-)  Meanwhile, I have determined it was caused by failing
> to recognize a valid alias.

I'm afraid the compiler is working as designed.

>          YYSTYPE  def,
>          YYSTYPE  list )
>  {
> +    tDefEntry*  ret   = (tDefEntry*)list;
>      tDefEntry*  pDef  = (tDefEntry*)def;
> -    tDefEntry*  pScn  = (tDefEntry*)list;
> -    tDefEntry** ppT   = (tDefEntry**)&list;
> +    tDefEntry*  pScn  = ret;
> +    tDefEntry** ppT   = &ret;

In the original code, the type-based aliasing rules permit the
compiler to assume that assignment to ppT does not modify list
EVEN THOUGH IT IS OBVIOUS TO A HUMAN THAT IT DOES.

Your fix is the right way to correct your code.  By immediately
assigning list to a temporary with its true type, you show the
compiler what's really going on.

zw