------- Comment #11 from redi at gcc dot gnu dot org 2010-06-11 14:56 -------
(In reply to comment #9)
> I understand now after the implicit promotion to int of a non constant value
> the result of the narrowing operation can't be guaranteed to fit in the
> original type. But I still think it shouldn't give an error, and if the
> standard says so, I think it is flawed in this regard ;-)
>
> Consider
>
> g<INT_MAX, INT_MAX>(); // Warning, but no Error
The integer overflow means this is undefined behaviour. But it is not a
narrowing conversion according to the rules of 8.5.4/6
> despite it can be proven that the value will not fit and this is very likely
> an
> error. Opposing to
>
> char c,d;
> A a = { c+d };
>
> which is very likely not an error and would only require a mild warning. IMHO.
use A a = { char(c+d) } if you want the result to be a char not an int, then
there is no narrowing conversion, because a narrowing conversion is an impliit
conversion.
(In reply to comment #10)iagnostic is IMHO clear.
> prefer a bit longer message:
>
> error: C++0x does not allow narrowing conversion of "(((int)y) + 1)" from
> "int"
> to "char" inside { }
I prefer the shorter message. If the compiler tells you there is an error it
doesn't normally tell you the standard says so. If you compile with -std=c++0x
then obviously that's the standard in question.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44500
