freeing memory in C doesn't work

Question

I have a problem when i try to free allocated memory in C.

int i,j,**redmatrix, **bluematrix, **greenmatrix;
double **weigthMatrix,fsom;
weigthMatrix = (double**) calloc(radius*2+1,sizeof(double*));
redmatrix = (int**) calloc(radius*2+1,sizeof(int*));
bluematrix = (int**) calloc(radius*2+1,sizeof(int*));
greenmatrix = (int**) calloc(radius*2+1,sizeof(int*));
if(weigthMatrix==NULL || redmatrix==NULL || bluematrix==NULL || greenmatrix==NULL){
    printf("%s\n", "Error: probleem met geheugenallocatie");
    exit(1);
}
for(i=0;i<radius*2+2;i++){
    weigthMatrix[i] = (double*) calloc(radius*2+1,sizeof(double));
    redmatrix[i] = (int*) calloc(radius*2+1,sizeof(int));
    bluematrix[i] = (int*) calloc(radius*2+1,sizeof(int));
    greenmatrix[i] = (int*) calloc(radius*2+1,sizeof(int));
    if(weigthMatrix[i]==NULL || redmatrix[i]==NULL || bluematrix[i]==NULL || greenmatrix[i]==NULL){
        printf("%s\n", "Error: probleem met geheugenallocatie");
        exit(1);
    }
}
for(i=0;i<radius*2+1;i++){
    free(weigthMatrix[i]);
    free(redmatrix[i]);
    free(bluematrix[i]);
    free(greenmatrix[i]);
}

free(redmatrix);    //MY PROGRAM CRASHES HERE
free(bluematrix);
free(greenmatrix);
free(weigthMatrix);
free_image(&copyImage);

My program crashes when i try to free the top level of my array. I don't know what i am doing wrong. I think I allocated everything right?

[OMG all those casts](http://stackoverflow.com/questions/605845/do-i-cast-the-result-of-malloc). And all that missing whitespace. — The Paramagnetic Croissant, Oct 24 '14 at 18:26
I think it's an array overrun -- `radius*2+1` in the `calloc` calls vs. `radius*2+2` in the loops. Why don't you use the same value throughout? — Fred Larson, Oct 24 '14 at 18:27
Oops, that was wrong in the answer, but i did write it correctly in my code, so that isn't the answer :) — Lennart, Oct 24 '14 at 18:29

score 3 · Accepted Answer · answered Oct 24 '14 at 18:29

You reserve space for radius*2+1 elements

redmatrix = (int**) calloc(radius*2+1,sizeof(int*));

But then you fill and free arrays with radius*2+2 elements

for(i=0;i<radius*2+2;i++){
    redmatrix[i] = (int*) calloc(radius*2+1,sizeof(int));

for(i=0;i<radius*2+2;i++){
    free(redmatrix[i]);
    ...

change to

for(i=0;i<radius*2+1;i++){
    redmatrix[i] = (int*) calloc(radius*2+1,sizeof(int));
    ...

for(i=0;i<radius*2+1;i++){
    free(redmatrix[i]);
    ...

And please, don't cast malloc

freeing memory in C doesn't work

1 Answers1