Template aliases don't work - c++

Question

I'm trying to get template aliases to work on clang but it doesn't work although the reference sheet says it does
~~~~>$ cat template_alias.cpp
#include <vector>
using namespace std;
template<typename T>
using DoubleVec = vector<vector<T>>;
int main() { return 0; }
~~~~>$ clang template_alias.cpp -o template_alias
template_alias.cpp:6:19: warning: alias declarations accepted as a C++0x extension [-Wc++0x-extensions]
using DoubleVec = vector<vector<T>>;
^
template_alias.cpp:6:34: error: a space is required between consecutive right angle brackets (use '> >')
using DoubleVec = vector<vector<T>>;
^~
> >
template_alias.cpp:6:1: error: cannot template a using declaration
using DoubleVec = vector<vector<T>>;
^
1 warning and 2 errors generated.
~~~~>$ clang -std=c++0x template_alias.cpp -o template_alias
template_alias.cpp:6:1: error: cannot template a using declaration
using DoubleVec = vector<vector<T>>;
^
1 error generated.
Am I doing it wrong?

Answer 1

Your second command (with -std=c++0x) is correct, as is your test case. You might be using a version of clang prior to its support for template aliases. You can check for this by doing:
#if __has_feature(cxx_alias_templates)
Here is a complete list of feature-test macros that clang uses:
http://clang.llvm.org/docs/LanguageExtensions.html#checking_upcoming_features
Here is one, somewhat unpleasant, way to deal with the transition period between support of template aliases and not:
#include <vector>
using namespace std;
#if __has_feature(cxx_alias_templates)
template<typename T>
using DoubleVec = vector<vector<T>>;
#else
template<typename T>
struct DoubleVec {
typedef vector<vector<T> > type;
};
#endif
int main()
{
#if __has_feature(cxx_alias_templates)
DoubleVec<int> v;
#else
DoubleVec<int>::type v;
#endif
}