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Tip of the Day
Language: C++
Expertise: Beginner
Feb 14, 2000

New Versus Malloc()

Question:
Why is it necessary to typecast the return value of malloc() but not for the new operator?

This question has been asked of many C++ experts but no one has given me a convincing answer.

Answer:
Unlike malloc(), operator new is aware of the type of the object it allocates because it needs to invoke the class' constructor before returning the allocated object's address. Since new is aware of the actual type of object being allocated, it automatically casts the returned pointer to the desired type for you.

By contrast, malloc() doesn't know which type of object it allocates. Therefore, when using malloc(), you need to specify the size of the object explicitly, as well as cast the returned pointer to the desired type.

This is a fertile source of errors; therefore, it's best to avoid using malloc() in C++ altogether.

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