Code that clang does not allow

default_template.cc

// Clang does not compile the code, but gcc does.
// See e.g.,
// http://www.mail-archive.com/llvmbugs@cs.uiuc.edu/msg08044.html
template <typename T>
class Foo {
 public:
  Foo() {}
  ~Foo() {}

  void func(int a);
};

template <typename T>
void Foo<T>::func(int a = 0) {}

int main() {
  Foo<int> foo;
  foo.func(1);

  return 0;
}