c++ - Using class member functions without initialization -

this question has answer here:

• accessing class members on null pointer 8 answers

why possible use class member functions on uninitialized object (at least believe it's uninitialized). following runs without error:

// a.h class {  public:   explicit a(int n) : n_(n) {};   ~a() {};   int foo() {     return n_;   };   int bar(int i) {     return i;   };  private:   int n_; }; 

with

// main.cc #include <iostream> #include "a.h"  int main(int argc, char **argv) {   *myclass;   std::cout << myclass->bar(5) << "\n"; } 

now, attempting myclass->foo();fails, why can use bar() when we've declared pointer a exists, , called myclass? acceptable coding style/is there ever reason use approach?

why can use bar() when we've declared pointer a exists, , called myclass?

because, in general, it's impossible compiler tell whether pointer valid @ runtime; isn't required diagnose error. however, in case, decent compiler should able issue warning, long you're not building warnings disabled.

is acceptable coding style/is there ever reason use approach?

absolutely not. dereferencing invalid pointer gives undefined behaviour.