Thread: correct malloc use

Hi all,
I 'm having a bit of trouble understanding about the use of malloc for 1d and 2d arrays., and I would appreciate if someone could tell me what is correct. Lets say for 1d arrays, which is correct?

vector = malloc(length*sizeof(vector));

or

vector = malloc(length*sizeof(*vector));

and for 2d arrays:

Code:

        matrix=malloc(rows*sizeof(matrix));
        for (i=0; i<columns; i++)
                matrix[i]=malloc(columns*sizeof(matrix[i]));

or

Code:

        matrix=malloc(rows*sizeof(*matrix));
        for (i=0; i<columns; i++)
                matrix[i]=malloc(columns*sizeof(*matrix[i]));

I've tried both with gcc and all warnings/pedantic flags on, but both produce the same result (and no warnings) when I put some values in vector and array and then display them.

I've also seen (assuming vector and matrix are unsigned integers

Code:

vector = malloc(length*sizeof(unsigned int*))

and

Code:

        matrix=malloc(rows*sizeof(unsigned int *));
        for (i=0; i<columns; i++)
                matrix[i]=malloc(columns*sizeof(unsigned int));

Ideally I'd like to avoid this in case I want to chenge the type of vector or matrix eg from float to double.

Thank you
Spiros