c – 重载char *和std :: string是否安全？

我玩下面的代码并获得一些结果.但我不确定它是否是一种未定义的行为.

void foo(std::string str) {
  cout << "This is the std::string version. " << endl;
}

void foo(char* str) {
  cout << "This is the char* version. " << endl;
}

int main(int argc,char *argv[]) {

  foo("Hello"); // result shows char* version is invoked

  std::string s = "Hello";
  foo(s); // result shows std::string version

  return 0;

}