C++: new call that behaves like calloc?

c++ new-operator calloc
nivnad picture nivnad · Apr 30, 2009 · Viewed 15.8k times · Source

Is there a call I can make to new to have it zero out memory like calloc?

Answer

Johannes Schaub - litb picture Johannes Schaub - litb · Apr 30, 2009

Contrary what some are saying in their answers, it is possible.

char * c = new char[N]();

Will zero initialize all the characters (in reality, it's called value-initialization. But value-initialization is going to be zero-initialization for all its members of an array of scalar type). If that's what you are after.

Worth to note that it does also work for (arrays of) class-types without user declared constructor in which case any member of them is value initialized:

struct T { int a; };
T *t = new T[1]();
assert(t[0].a == 0);
delete[] t;

It's not some extension or something. It worked and behaved the same way in C++98 too. Just there it was called default initialization instead of value initialization. Zero initialization, however, is done in both cases for scalars or arrays of scalar or POD types.

Related questions

In what cases do I use malloc and/or new?

I see in C++ there are multiple ways to allocate and free data and I understand that when you call malloc you should call free and when you use the new operator you should pair with delete and it is …

Read More
Expression must have class type

I have't coded in c++ for some time and I got stuck when I tried to compile this simple snippet: class A { public: void f() {} }; int main() { { A a; a.f(); // works fine } { A *a = new A(); a.f(); // this …

Read More
Creating an object: with or without `new`

Possible Duplicate: What is difference between instantiating an object using new vs. without This is probably a basic question, and might have already been asked (say, here); yet I still don't understand it. So, let me ask it. Consider the …

Read More