creating a shared_ptr from unique_ptr

Question

In a piece of code I reviewed lately, which compiled fine with g++-4.6, I encountered a strange try to create a std::shared_ptr from std::unique_

Answer 1

Here's a reduced example which clang incorrectly compiles:

struct ptr
{
  int* p;

  explicit operator bool() const { return p != nullptr; }
};

int main()
{
  ptr u{};
  int* p = new int(u);
}

Clang uses the explicit bool conversion operator to initialize the int (and the Intel compiler does too.)

Clang 3.4 does not allow:

int i = int(u);

but it does allow:

int* p = new int(u);

I think both should be rejected. (Clang 3.3 and ICC allow both.)

I've added this example to the bug report.