Re: [PATCH 16/16] fix handling of integer constant expressions

[Al Viro <viro@ftp.linux.org.uk>]

On Wed, Jun 27, 2007 at 03:06:36PM +0100, Al Viro wrote:
> *unprintable*
> 
> Yes, I see...  OK, null pointer constants handling (next patch in the
> queue) introduces is_zero_constant() (silent evaluation of integer
> constant expression, with division by 0/too large shift/- on lowest
> value of signed integer type leaving the branch as-is, so that later
> expand would generate a proper error on it; then checking if we'd
> reduced the sucker to EXPR_VALUE[0]).  I'll pull it into a separate
> patch, along with is_nonzero_constant(), and change rules for potential
> ICE on parser stage to
> 	maybe-ICE && y => maybe-ICE
> 	maybe-ICE || y => maybe-ICE
> 	maybe-ICE ? x : y => maybe-ICE if at least one of x and y is maybe-ICE
> 	maybe-ICE ? : y => maybe-ICE
> letting evaluate_expression() on such suckers use them if the first argument
> turns out to be ICE after its evaluate_expression()...
> 
> It really stinks, especially since we can't say "oh, parent it known to
> be non-ICE, no need to bother" - subexpression might be shared.

... or it could be done simpler, if we keep the current logics for
Int_const_expr flag at parse time and add a 'const expression' one
with rules as above.  Anyway, I'm going to get some sleep before
dealing with that crap.