[Bug c/43128] [4.5 Regression] c-c++-common/pr41779.c doesn't work

["joseph at codesourcery dot com" <gcc-bugzilla@gcc.gnu.org>]

------- Comment #23 from joseph at codesourcery dot com  2010-02-23 16:38 -------
Subject: Re:  [4.5 Regression] c-c++-common/pr41779.c doesn't
 work

On Tue, 23 Feb 2010, manu at gcc dot gnu dot org wrote:

> ------- Comment #21 from manu at gcc dot gnu dot org  2010-02-23 10:23 -------
> (In reply to comment #19)
> > 
> > The present logic is: convert (with convert_and_check) both operands to a 
> > common type, which may have excess precision; then, later, after producing 
> > the tree for the result of the operation, wrap that in an 
> > EXCESS_PRECISION_EXPR, using the semantic type, if there is a semantic 
> > type different from the type with excess precision.
> 
> This is only true for build_binary_op. In build_conditional_expr both operands
> are converted to the semantic type first, if I am reading the code correctly,
> so there is nothing to fix (in fact, I cannot build a testcase that misses the
> warning when using conditional expression).

No, the conversion is to the type with excess precision.  Try:

float a;  
int b;
int c;           
long double f(void) { return c ? a + a : b; }

If you use "a" instead of "a + a", then it's just a float rather than a 
long double wrapped in an EXCESS_PRECISION_EXPR.  build_binary_op 
explicitly adds excess precision early on for various operations where it 
is necessary to describe the semantics of what the processor can do.  But 
there is no need to add excess precision for a conditional expression - 
just to handle operands that already have it.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43128