Travis Vitek wrote:
[...]
The problem is that many of the trait tests do this type of
thing. I can work around this pretty easily by explicitly
instantating each template in each test, but this is tedious
(there are many).
I'm not sure I understand why you are even considering working
around it. Doesn't the bug make the built-in traits pretty much
unusable in generic code?
Not always. If the template is instantiated the error would not be seen.
The reason I ask is because I couldn't get even a simple SFINAE
test program to compile. I think the program is well-formed even
though gcc 4.3.0 chokes on too (albeit for a different reason --
see http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36797)
$ cat t.cpp && eccp -A t.cpp
#include <assert.h>
template <int> struct S { };
template <class, bool> struct enable_if;
template <class T> struct enable_if<T, true> { typedef T type; };
template <class T>
int foo (typename enable_if<T, __is_empty (T)>::type* = 0) { return 0; }
template <class T>
int foo (typename enable_if<T, !__is_empty (T)>::type* = 0) { return 1; }
int main ()
{
assert (0 == foo<S<0> >());
assert (1 == foo<int>());
}
"t.cpp", line 16: error: no instance of overloaded function "foo"
matches the
argument list
assert (0 == foo<S<0> >());
^
1 error detected in the compilation of "t.cpp".
Martin
I was thinking about doing something like this...
#define _INSTANTIATE(T) \
typedef typename \
__rw_conditional<__rw_is_class_or_union<T>::value, \
T::type, \
void>::type _RWSTD_PASTE(dummy, __LINE__);
And then sneaking a void typedef into each of my user
defined types, and
then using this macro in the TEST () macro that I use all over the
tests. Is there a better way?
Travis
