memo: nullptr confuses decltype(auto).

1.cc

#include <stdio.h>
#include <malloc.h>

template <typename T>
auto my_alloc() -> decltype(auto) {
  auto ret = static_cast<T*>(malloc(sizeof(T)));
  if (ret == NULL) {
    return nullptr;
  }
  return ret;
}

int main() {
  auto a = my_alloc<int>();
  free(a);
  return 0;
}

It's not compilable on my env. How about on yours?

I've checked on there, but get errored.
clang version 3.4.2 (tags/RELEASE_34/dot2-final)
Target: i386-pc-cygwin
Thread model: posix

I've checked another env, failed.

$ clang++ 1.cc -std=c++1y
1.cc:10:3: error: 'decltype(auto)' in return type deduced as 'int *' here but
      deduced as 'nullptr_t' in earlier return statement
  return ret;
  ^
1.cc:14:12: note: in instantiation of function template specialization
      'my_alloc<int>' requested here
  auto a = my_alloc<int>();
           ^
1 error generated.

$ clang++ --version
clang version 3.5.0 (220663)
Target: x86_64-unknown-linux-gnu
Thread model: posix