nullptr

#include <iostream>void foo(char *){    std::cout << "void foo(char *)" << std::endl;}void foo(int){    std::cout << "void foo(int)" << std::endl;}int main(int argc, char** argv){  char* pc = nullptr;     // OK  int * pi = nullptr;     // OK  //int    i = nullptr;     // error  //nullptr.cpp:18:14: 错误：不能在初始化时将‘std::nullptr_t’转换为‘int’    foo(nullptr);           // 呼叫 foo(char *)   foo(0);   //foo(NULL);       //nullptr.cpp:22:12: 错误：调用重载的‘foo(NULL)’有歧义   //nullptr.cpp:22:12: 附注：备选是：   //nullptr.cpp:4:6: 附注：void foo(char*)   //nullptr.cpp:9:6: 附注：void foo(int)   return 0;}