CODEWITHSUNDEEP
c
secluded
secluded

Reputation: 517

What does sizeof(int**) mean?

I am new to C. I saw this line in a program:

grid = calloc(nx,sizeof(int**));

I read that int** means a pointer to a pointer, but what is meant by sizeof(int**)??

Upvotes: 2

Views: 3890

Answers (3)

D Hydar
D Hydar

Reputation: 501

The sizeof expression is just the number of bytes needed to represent a pointer-to-pointer-to-int. Presumably, whoever wrote the code is looking to allocate enough memory to store nx such pointers.

Upvotes: 2

John Bode
John Bode

Reputation: 123458

The sizeof operator yields the number of bytes of storage required by its operand. The operand is either an expression or a type enclosed in parentheses. In this case, the operand is the type int **, which is "pointer to pointer to int".

Assuming grid has been declared as 

int ***grid;

then that can be rewritten as

grid = calloc(nx, sizeof *grid);

Upvotes: 3

dbush
dbush

Reputation: 223872

sizeof(int **) tells you how many bytes an int ** is, similarly to how sizeof(int *) tells you how many bytes an int * is. They just have different levels of indirection.

Upvotes: 1

Related Questions