malloc help - segmentation fault

[shoobyman]

I have to make a program that takes an input matrix (in a 2D array) and output it's inverse. The problem i have is allocating memory to the dynamic array. And yes, it must be a dynamic array and it must use malloc to allocate the memory. Please help, it's been KILLING me for the past couple days. It compiles, but when i run it i get a segmentation fault.

code:

int main (void) {         int size, i;         printf ("Enter dimension of square matrix:");         scanf ("%d", &size);         double **entries = (double **)malloc(size*size*sizeof(double));            // HERE IS WHERE THE PROBLEM (probably) IS         printf ("\nEnter the %d entries of the matrix:", size*size);         for (i=0; i<size; i++)         {                 int j;                 for (j=0; j<size; j++)                 {                         scanf ("%lf", &entries [i][j]);                 }         }         free (**entries);         return 0; }

Thanks is advance.

[OneOffDriveByPoster]

shoobyman @ Thu Nov 06, 2008 7:11 pm wrote:

c:

double **entries = (double **)malloc(size*size*sizeof(double));            // HERE IS WHERE THE PROBLEM (probably) IS

Yes, your malloc did not do what you expected it to. You allocated a block of sizeXsize doubles and not size# of double* pointing to size# of doubles. You can access this like a one-dimensional array for example.

What are the requirements? Why do you have to use malloc? C has variable length arrays.