Saturday, August 27, 2011

smart ptr is 50% similar to a raw ptr

I'd say it's 90% different and 10% similar to a raw ptr. Smart pointers are class objects, way beyond 32-bit pointers. smart pointers overload de-referencer and many other operators to "look like" a raw pointer, but it's really a class-template (Avoid the non-standard "template-class" jargon)

- pbclone? A raw pointer is always passed by clone (bitwise clone), just as in java. Smart pointers override copier (and op=), so a new instance is created based on the RHS smart pointer instance. Is this pbclone or pbref? I'd say more like pbclone.
- When you dereference a raw ptr, you simply follow the pointer. Smart pointer dereference is a high-level user-defined operation.
- You can up/down cast raw pointers, not smart pointers.
- a raw ptr can be cast to void ptr. A smart ptr can't.
- Raw pointers are key to virtual functions, not smart pointers.
- Creation and initialization is simple for raw pointers.
- size? A Smart pointer exceeds 32 bits except intrusive_ptr
- raw ptr has tight integration with arrays, with pointer arithmetic. Not smart ptr.
- double ptr sematics with 2 stars is natural for raw ptr, not smart ptr
- delete
- new? we can put raw ptr as lvalue of a "new" expression
- null assignment

In conclusion, raw pointers are such a part of the fabric. As a crude analogy, an e-book can feel like a paper book, but you can't fold corners; can't write anywhere using any pen; can't spread 3 books out on your table; can't tear off a page; can't feel the thickness

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http://www.linkedin.com/in/tanbin