2015-08-31 21:43 GMT+02:00 Kai Tietz <ktiet...@googlemail.com>:
> 2015-08-31 21:29 GMT+02:00 Jason Merrill <ja...@redhat.com>:
>> On 08/31/2015 03:08 PM, Kai Tietz wrote:
>>>
>>> I will need to verify that this patch doesn't introduce regressions.
>>> The wacky thing here is the encapsulation of overflowed-arguments in
>>> maybe_constant_value function by nop-expr.
>>
>>
>> Do we need to worry about that? If one of the operands is overflowed, we
>> don't care whether the result is overflowed.
>
> Well, we would introduce, if we don't see in condition that operand
> already overflowed, double overflow-warning, which seems to be
> something we avoided until now. So I would say, it matters.
>
> Kai
Similar to the binary-operation we want to do then the same for
unary-operations, too.
Eg. testcase:
#include <limits.h>
constexpr int f() { return INT_MIN; }
int main()
{
return -f(); // { dg-warning "overflow" }
}
With following patch we do diagnostics for it.
Kai
Index: semantics.c
===================================================================
--- semantics.c (Revision 227339)
+++ semantics.c (Arbeitskopie)
@@ -2553,9 +2553,11 @@ finish_unary_op_expr (location_t loc, enum tree_co
tree result = build_x_unary_op (loc, code, expr, complain);
tree result_ovl = result;
- expr_ovl = fold_simple (expr_ovl);
- result_ovl = fold_simple (result);
-
+ expr_ovl = maybe_constant_value (expr_ovl);
+ result_ovl = maybe_constant_value (result);
+ /* Strip nop-expressions added by maybe_constant_value on overflow. */
+ STRIP_NOPS (expr_ovl);
+ STRIP_NOPS (result_ovl);
if ((complain & tf_warning)
&& TREE_OVERFLOW_P (result_ovl) && !TREE_OVERFLOW_P (expr_ovl))
overflow_warning (input_location, result_ovl);
