C++: Global variable as pointer

问题:

I am new to c++ and have one question to global variables. I see in many examples that global variables are pointers with addresses of the heap. So the pointers are in the memory for global/static variables and the data behind the addresses is on the heap, right?
Instead of this you can declare global (no-pointer) variables that are stored the data. So the data is stored in the memory for global/static variables and not on the heap.
Has this solution any disadvantages over the first solution with the pointers and the heap?

Edit:
First solution:

//global 
Sport *sport;
//somewhere
sport = new Sport;

Second solution:

//global
Sport sport;

回答1:

You are right in your hypothesis of where the objects are located. About usage,
It's horses for courses. There is no definite rule, it depends on the design & the type of functionality you want to implement. For example:
One may choose the pointer version to achieve lazy initialization or polymorphic behavior, neither of which is possible with global non pointer object approach.

回答2:

Right. Declared variables go in the DataSegment. And they sit there for the life of the program. You cannot free them. You cannot reallocate them. In Windows, the DataSegment is a fixed size....if you put everything there you may run out of memory (at least it used to be this way).

回答3:

A disadvantage of storing your data in a global/static variable is that the size is fixed at compile time and can't be changed as opposed to heap storage where the size can be determined at runtime and grow or shrink repeatedly over the run. The lifetime is also fixed as the complete run of the program from start to finish for global/static variables as opposed to heap storage where it can be acquired and released (even repeatedly) all through the runtime of the program. On the other hand, global and static storage management is all handled for you by the compiler where as heap storage has to be explicitly managed by your code. So in summary, global/static storage is easier but not as flexible as heap storage.