I have an integer variable x that I need to use to make two 2D arrays but I get an error of "cannot allocate an array of constant size 0". After doing some research I apparently need to use malloc but I have no idea how to apply it to my currently situation.
My two arrays I need:
int firMat[x][5];
int secMat[5][x];
#include <stdio.h>
#include <stdlib.h>
int main(void) {
int x = 2;
int **firMat;//int firMat[x][5];
int **secMat;//secMat[5][x];
int i;
firMat = malloc(x * sizeof(int*));
for(i = 0; i< x; ++i)
firMat[i] = malloc(5 * sizeof(int));
secMat = malloc(5 * sizeof(int*));
for(i = 0; i< 5; ++i)
secMat[i] = malloc(x * sizeof(int));
//do stuff E.g. fir[2][1] = 21;
//release E.g.
//for(i = 0; i< x; ++i)
// free(firMat[i]);
//free(firMat);
return 0;
}
If you're using C99, this will work. It will create a "variable-length array", sadly VLAs have been reduced to "optional" in C11.
To use malloc for this, typically I'd abandon the double-array notation, and treat the memory as a flat one-dimensional array, then array[i][j] becomes ptr[ i*cols + j ].
Try to initialize x like in the example below
#define x 2 //outside the function
and then use x like this
int firMat[x][5];
int secMat[5][x];
xbefore this?