How to initialize a dynamic int array elements to 0 in C

Question

I created a dynamic array ,and i need to initialize all the members to 0. How can this be done in C?

   int* array;
    array = (int*) malloc(n*sizeof(int));

Answer 1

In this case you would use calloc():

array = (int*) calloc(n, sizeof(int));

It's safe to assume that all systems now have all zero bits as the representation for zero.

§6.2.6.2 guarantees this to work:

For any integer type, the object representation where all the bits are zero shall be a representation of the value zero in that type.

It's also possible to do a combination of malloc() + memset(), but for reasons discussed in the comments of this answer, it is likely to be more efficient to use calloc().

Answer 2

memset(array, 0, n*sizeof(int));

Or alternatively, you could allocate your block of memory using calloc, which does this for you:

array = calloc(n, sizeof(int));

calloc documentation:

void *calloc(size_t nmemb, size_t size);

The calloc() function allocates memory for an array of nmemb elements of size bytes each and returns a pointer to the allocated memory. The memory is set to zero. ...

Answer 3

Use calloc function (usage example):

int *array = calloc(n, sizeof(int));

From calloc reference page:

void *calloc(size_t nelem, size_t elsize);

The calloc() function shall allocate unused space for an array of nelem elements each of whose size in bytes is elsize. The space shall be initialized to all bits 0.