Why should I use new and not malloc()?

shabbir's Avatar, Join Date: Jul 2004
Go4Expert Founder
Just got a Mail from a user asking for a question as and thought also after answering him would like to share the same with Expert Advice Forums member

Why should I use new and not malloc()?

» Constructors/destructors:
New and Delete makes sure that constructors and Destructors are called but not the case with malloc and free functions of C.
» Pointer conversion safety:
malloc() returns a void* which isn't safe. new returns a pointer of the right type.
» new is a Operator:
new is an operator that can be overloaded for better memory management by a class, while malloc() is not an operaotor.
0
Aztec's Avatar, Join Date: May 2006
Contributor
Just to add few more things

>new operator computes the size of object automatically whereas malloc cannot.
>It is possible to initialize the object while allocating memory with new.
0
poornaMoksha's Avatar, Join Date: Jan 2011
Ambitious contributor
Adding one more point :

- Its possible to construct an object over an already allocated memory using another version of 'new' operator known as 'placement new' operator. While with malloc() it is not possible.
0
lipun4u's Avatar, Join Date: Jan 2010
Light Poster
certain disadvantage of new...

if the class doesn't have a default constructor, new can't be used to allocate memory for that object.

Please tell if i am right ?
0
poornaMoksha's Avatar, Join Date: Jan 2011
Ambitious contributor
From Wikipedia :

Quote:
The compiler will implicitly define a default constructor if no constructors are explicitly defined for a class. This implicitly-declared default constructor is equivalent to a default constructor defined with a blank body. (Note: if some constructors are defined, but they are all non-default, the compiler will not implicitly define a default constructor. This means that a default constructor may not exist for a class.)
0
lipun4u's Avatar, Join Date: Jan 2010
Light Poster
But the situation is if I have class with a parametrized constructor and no other constructor at all.
0
poornaMoksha's Avatar, Join Date: Jan 2011
Ambitious contributor
In this case too, new can be used to allocate memory and construct object.
Quote:
Originally Posted by lipun4u View Post
But the situation is if I have class with a parametrized constructor and no other constructor at all.
0
xpi0t0s's Avatar, Join Date: Aug 2004
Mentor
To create a class that cannot be instantiated with new you need to declare a private constructor. Of course, you will need to pair this with a friend class that will be able to create objects, otherwise you won't be able to create any objects of the first type at all, which would be rather pointless.
0
GaneshShinde's Avatar, Join Date: Oct 2011
Newbie Member
One question just poped in my head while reading this, it may be irrelevant to ask in this question.
Question is what is the similar unctions or operators for realloc, calloc like C language?
0
GaneshShinde's Avatar, Join Date: Oct 2011
Newbie Member
Corrected from last post
Quote:
Originally Posted by GaneshShinde View Post
One question just poped in my head while reading this, it may be irrelevant to ask in this question.
Question is what is the similar functions or operators in c++ for realloc, calloc like C language?