Thread: confused with declrartions...

I have following code please see the declarations of array

Code:

int main()
{

//How is this different from the below declarations
 int *x[10];

//Another declaration
 int ( *x)[10];


 return 0;
}

What would be size of each declarations?

Does this declaration int ( *x)[10] and int *x[10] mean array containing pointers.
Shouldn't the size will be sizeof(int)*10 = 40.

Thanks in advance

These are two kinds of declaration for an array of integers:

Code:

int x[10];    /* allocated at compile time, each position has the size of an int */

int *x;        /* it's the same with the difference that the memory allocated at compile time is just for a pointer,
                    you will need to allocate it dinamically with malloc */

while these are a bit different

Code:

int *x[10]   /* at compile time, sizeof(int*)*10 is allocated, thus is an array of pointers to integers */

int **x;      /* as above with tthe difference that the memory allocated at compile time is just for a pointer
                   you will need to allocate it dinamically */

the advantage of allocate arrays dinamically is that you can manage their size at run time.

hope that help.

Thanks for ur time..

Originally Posted by flexo87

These are two kinds of declaration for an array of integers:

Code:

int **x;      /* as above with tthe difference that the memory allocated at compile time is just for a pointer
                   you will need to allocate it dinamically */

So your mean

int **x is same as int (*x)[10].........Can u explain this?


What would be the size that will be allocated?

It is not the same, with the first (int** x) you are telling the compiler to not allocate memory for the array (you will do it in the program).
with the second (int *x[10], i thnk brackets are unnecessary) the compiler will allocate the space in order to contain 10 pointers to an integer, so the memory you will need to allocate is to contain the integers, while in the first case you allocate memory to contain pointers, and then integers.

Code:

int **x;   /* allocate sizeof(int**), 4 bytes */

int *x[10];   /* allocate sizeof(int*)*10, 40 bytes */

Thanks...

Originally Posted by laserlight

This declares a pointer, named x, to an array of 10 pointers to int:

Code:

int (*x)[10];

How different is it from declaring

so

Code:

int *x and int (*x)[10]

is one and the same?

What would be the advantage with the declaration

Code:

int (*x)[10]

?