std :: cout是否初始化（或预初始化）指针？

Question

I have a question about pointers in C++.

I know you can't delete a uninitialized pointer and if you want to use , the pointer should be initialized first. But does somehow "initialize" it?
If I try to run the code below it will crash during the execution.

#include <iostream>
int main (){
   int *ptr;
   delete ptr;
   return 0;
}

This is what I'd expect and I'm fine with it because the pointer is not initialized. However if I try to run the code below it won't crash!

#include <iostream>
int main (){
   int *ptr;
   std::cout << ptr << std::endl; //This is the new line
   delete ptr;
   return 0;
}

I know that the pointer is not initialized because I can't assign anything to it, if I add this line before the

*ptr = 5;

The program will crash as expected. Why, then the program won't crash if I use the before delete? I know didn't initialize the pointer, but is this somehow a "pre-initialization"(or something else)?
Thanks!
Ezra

Answer 1

Deleting an uninitialized pointer is undefined behavior.

Undefined behavior may crash your program, if you are lucky. You were unlucky, and your program did not crash.

In this case, when you call delete ptr , the compiler knows that the ptr is garbage. Perhaps it just calls delete with whatever value is handy, and if you use cout , nullptr just coincidentally happens to be that value.