Can't understand if deallocation happens?

[Suliman via Digitalmars-d-learn]

> str_ptr.ptr returns exactly the same thing as str.ptr or 
> (*str_ptr).ptr, a pointer to the contents. When you write 
> str_ptr, you print the pointer to the container.

So str.ptr is just shortcut?

Ok, but how to free memory from first located value (from `aaa`)?

I changed my code to next:

import std.stdio;
import std.string;
import core.memory;

void main()
{
     string str = "aaa".dup;
     string *str_ptr = &str;

     writeln("before: ", str_ptr.ptr);// address of structure
     writeln(*str_ptr.ptr); // address of data
     str = "bbbb"; // now writing to structure new data, so ptr 
would be point to them
     writeln("after: ", str_ptr.ptr);
     writeln("length: ", str_ptr.length);
     writeln("str_ptr point to: ", *str_ptr.ptr);

     writeln(str_ptr);
	
	writeln("before dealloc: ", str_ptr.length);
     //GC.free(str_ptr.ptr); // Error: function 
core.memory.GC.free (void* p) is not callable using argument 
types (immutable(char)*)
     writeln(str_ptr);
     writeln("after dealloc: ", str_ptr.length);

}

But I can't call `GC.free(str_ptr.ptr)` on string type, only on 
`char []`