Question

I am having difficulties to remember whether in c++ a local (non static, and inside a block) variable defined in the block is destroyed or not as long as a pointer points to it, even after the execution leaves the block.
So if I created a int inside a block, and have a global pointer, and I leave the block, can my pointer still find that int?

I didn’t finding a clear answer to this online, though it’s probably been answered more than once, sorry about that.

Answer 1

No, you’re in undefined behavior territory.

I’m assuming you mean something like:

int* p = NULL;
{
   int x = 0;
   p = &x;
}
//p is a dangling pointer

If you attempt to dereference p after }, you’ll run into trouble (or, worse, you won’t and it will look like it’s working).

You can however re-assign the pointer, so something like

p = new int();

is perfectly OK.

The following would be legal though (as an alternative to allocating dynamic memory with new or malloc):

int* p = NULL;
{
   static int x = 0;
   p = &x;
}
*p = 0;