what is the difference between Malloc and new operator to allocate a memory?

Question

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What is the difference between new/delete and malloc/free?

I was confused when I create an object by using new operator in C++. There must be difference between malloc and new operator that would allow me to resize the memory block. If I want to allocate a memory I use malloc but what if I use a new operator?

İsn't it allocate a memory? Can you explain that when shoul I use malloc and when should I use new ?

X* ptr = new(1,2) X;

obj = (ObjID *)malloc( sizeof(ObjID) );

thanks so much.

Answer 1

new allocates memory and also calls the class constructor for the type you are allocating.

Answer 2

new will not only allocate you memory for objects but will also call the constructor on the objects created. malloc will just allocate you a block of memory of the given size with no guarantee of the contents.

Answer 3

In C++ you should always use new and pair it with delete.

• It calls constructor(s) for the object(s).
• Since it is an operator, it can be overloaded.
• It throws exceptions, but there is an exceptionless version.
• There is a "placement new", which allows you to put your object in already allocated memory.

Answer 4

malloc gives you raw memory with garbage bytes left around. New uses malloc internally, too. Use malloc if raw memory is all you need.