C ++ 11 Unified Function Initialization and Overloading

Question

Simple program:

void f(const std::string& s);
void f(const char* p);
f({});

Why does clang call f((const char*)nullptr)? I was expecting a compiler warning about an ambiguous call.

Answer 1

This is described in the standard section of the C ++ 11 project 13.3.3.1.5[over.ics.list], which states:

Otherwise, if the parameter type is not a class:

[...]

• if there are no elements in the initializer list, the implicit conversion sequence is an identity transformation. [Example:

  void f(int);
  f( { } ); // OK: identity conversion
  

-end example]

and therefore identity conversion would be better than calling the constructor.

, nullptr, , , . 8.5.4 [dcl.init.list]:

- T :

[...]

• , , . [:

  int** pp {}; // initialized to null pointer
  

-end ]