Assigned `nullptr` to `bool` type. Which compiler is correct?

Question

I have a following snippet of code that assigned nullptr to bool type.

#include <iostream>

int main()
{
    bool b = nullptr;
    std::cout << b;
}

In clang 3.8.0 working fine. it's give an output 0. Clang Demo

But g++ 5.4.0 give an error:

source_file.cpp: In function ‘int main()’:
source_file.cpp:5:18: error: converting to ‘bool’ from ‘std::nullptr_t’ requires direct-initialization [-fpermissive]
         bool b = nullptr;

Which compiler is correct?

Answer 1

From the C++ Standard (4.12 Boolean conversions)

1 A prvalue of arithmetic, unscoped enumeration, pointer, or pointer to member type can be converted to a prvalue of type bool. A zero value, null pointer value, or null member pointer value is converted to false; any other value is converted to true. For direct-initialization (8.5), a prvalue of type std::nullptr_t can be converted to a prvalue of type bool; the resulting value is false.

So this declaration

bool b( nullptr );

is valid and this

bool b = nullptr;

is wrong.

I myself pointed out already this problem at isocpp