On 3/6/2012 9:28 PM, Daniel Walker wrote:
On Mar 6, 2012, at 11:59 PM, Eric Niebler wrote:
On 3/6/2012 8:45 PM, Daniel Walker wrote:
On Mar 6, 2012, at 11:09 PM, Eric Niebler wrote:
On 3/6/2012 6:27 PM, Daniel Walker wrote:
On Mar 6, 2012, at 9:04 PM, Eric Niebler wrote:
On 3/6/2012 5:10 PM, Michel Morin wrote: > BTW, BOOST_NO_DECLTYPE_N3276 needs to be a more descriptive name?
I couldn't think of a better name, and BOOST_NO_DECLTYPE_ON_FUNCTION_CALL_EXPRESSION_FORCES_TYPE_COMPLETENESS is too long.
:-P
How about BOOST_NO_INCOMPLETE_DECLTYPE?
Ambiguous. Does that mean that decltype support is incomplete or that decltype doesn't force type-completeness?
BOOST_NO_INCOMPLETE_DECLTYPE means the compiler does not support incomplete decltypes; i.e. it does not support decltype expressions that are incomplete types.
But that's not the issue. The issue is this:
template<typename T> struct S {}; template<typename T> S<T> fun(T) {} typedef decltype(fun(0)) Si_t; // HERE
Does the third line force the instantiation of S<int>?
Decltype works just fine on incomplete types in the simple case, so far as I know:
struct S; extern S s; typedef decltype(s) S_t; // OK
Oh yeah, I forgot this only comes up with call expressions. How about BOOST_NO_INCOMPLETE_DECLTYPE_CALL_EXPRESSIONS? The macro means the compiler does not support incomplete decltypes of call expressions.
That's better, I suppose. It's not 100% accurate to say that the compiler doesn't support incomplete call expressions, though. If a compiler doesn't implement N3276, it still supports incomplete call expressions and usually gets the right answer, but it could potentially instantiate a template unnecessarily in the process. (And this could set off an infinite cascade of such template instantiations, which causes your computer to catch fire and burn off your eyebrows.) So I dunno. I still lean toward BOOST_NO_DECLTYPE_N3276 because nothing pithy seems to really get at the gist of it. And I don't expect this macro to be used outside of Boost itself. But I don't have a strong feeling about it. -- Eric Niebler BoostPro Computing http://www.boostpro.com