2015-09-01 10:43 GMT+02:00 Kai Tietz <ktiet...@googlemail.com>:
> 2015-09-01 10:15 GMT+02:00 Kai Tietz <ktiet...@googlemail.com>:
>> 2015-08-31 22:19 GMT+02:00 Kai Tietz <ktiet...@googlemail.com>:
>>> 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);
>>
>> I committed patches for binary & unary operations together with
>> testcases. Regression-run still running. There seems to be
>> additional expressions needed in constexpr for this. For now we have
>> a bootstrap-issue due cast_expr in cxx_eval_constant_expression.
>> There might be more of them ...
>
> I had to add for now that cxx_eval_constant_expr ignores on CAST_EXPR,
> STATIC_CAST_EXPR, OVERLOAD, and TREE_LIST. Additionally we need to
> handle for increments that offset is NULL_TREE (TREE_OPERAND (,1)) .
Issue was easier to resolve by checking in binary/unary
overflow-checking-functions that we aren't processing template
declarations. If we aren't within template-declaration processing we
can call maybe_constant_value. This avoids that we feed
maybe_constant_value with mentioned C++-template specific expressions.
Bootstrap ran successful, regression-testing still running for it. I
committed additional check already to branch.
Kai
