Wednesday, June 25, 2008

##varieties of c++ variables -- 4 dimensions

To understand the wide variety of C++ variables, consider...
-- about the object --
1) Heap (=>pointer) ^ stack
2) Primitives ^ class types
-- about the variable --
3) Pointer(and ref) ^ nonref types
4) locals ^ fields -- globals are rare
First 3 dimensions make 8 types
* Pointer/ref to Heap primitive
* pointer/ref to Heap class type
* pointer/ref to anything on stack is questionable[1]
* class type on heap but not accessed by pointer? impossible
* class type on stack and not accessed by pointer
* primitive on heap but not accessed by pointer? impossible
* primitive on stack and not accessed by pointer

[1] but how about simple c-strings. I used many of them without malloc(). Some arrays do live on the stack!

Nonref types can be pbclone or pbref. Pointers should be passed as ...pointers.

Vast majority of variables are local variables or fields. By default locals live on the stack, but a local ptr can point to a heap object. After out-of-scope, the heap leaks....;)

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