CODEWITHSUNDEEP
cpointersmemory
Chen
Chen

Reputation: 376

Pointer variable inside a function points to stack or heap?

void foo (char *input) {
  char *myVar;
  *myVar = *input;
}

I understand that if I allocate myVar memory using malloc(sizeof(char) it will point to heap, but what if I don't allocate the memory, when I deference it, how the compiler handles the memory allocation? will it be allocated in stack or heap?

Upvotes: 0

Views: 201

Answers (2)

Some programmer dude
Some programmer dude

Reputation: 409196

The variable myVar is on the stack (for compilers which store local variables on the stack), but it doesn't point anywhere. That means when you dereference it you have undefined behavior.

Technically, the value of myVar will be indeterminate (i.e. seemingly random) so it will point to a random location. This means that the dereference may sometimes cause a crash, while other times it may not.

Upvotes: 4

alk
alk

Reputation: 70941

when I deference it, how the compiler handles the memory allocation

Dereferencing a pointer's value (an address) is not allocating memory. Dereferencing just gives you access to the memory the reference, that is the pointer points to.

From where this memory had been allocated (if ever) depends on what had been assigend to the pointer. ls.

Note: Dereferencing an uninitialised pointer provokes undefined behaviour, as it does for any read-accees to uninitialised memory/variables.

Upvotes: 2

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