Reallocating memory of a C++ array. [duplicate]

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Possible Duplicate:
How do you realloc in C++?

I know that C++ arrays can be reallocated (expanded) using realloc() if memory has been allocated via malloc() or calloc(). My question is, how can I expand an array in C++ whose memory has been allocated via the new operator?

Answer 1

You can't - that's why in C++ you use std::vector<>.

If you wanted to do this, you'd have to allocate a new array (via new), then copy the old items across (std::copy for example), then delete[] the previous array.

Just use std::vector - let it do all that stuff for you...

Answer 2

In general C++ arrays cannot be reallocated with realloc, even if the storage was allocated with malloc. malloc doesn't give you arrays. It gives pointers to usable storage. There's a subtle difference here.

For POD types, there's little difference between usable storage and actual objects. But for non-POD types, usable storage and objects are totally different things.

realloc gives you a larger portion of usable storage. It manipulates storage not objects. That may work fine for POD types, but for other types it's a recipe for disaster.

Answer 3

Use ::std::vector.

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