C - program crashes when using free function

Question

first, sorry for my bad english jeje. I don't speak it.

I'm having a problem when using free() function to free memory, this is what I have :

I'm using codeblocks on Windows 7. I have around 3 years using dinamic memory allocation and this is the first time I get this problem. There are people that say that the problem is gcc compiler

Directions are equal in and out the function, so I don't think I'm trying to free an invalid pointer

Answer 1

The errors in the code is:

• M == NULL is not a valid way to check if malloc is succeeded. You should use (*M) == NULL because the value is assigned to (*M), not M.
• The loop condition in ReservarMemoriaMatriz i<=m seems wrong. It should be i<=n.
• You forgot to free (*M)[n] in LiberarMemoriaMatriz.

Corrected code:

void LiberarMemoriaMatriz(double*** M,int n){
    int i = 0;
    if(M == NULL) return;
    for(i=0; i<=n; i++){
        free((*M)[i]);
    }
    free(*M);
}

int ReservarMemoriaMatriz(double*** M, int n, int ,){
    int i = 0;
    if(M == NULL) return 0;
    (*M) = malloc((n+1)*sizeof(double*));
    if((*M) == NULL){
        return 0;
    }
    for(i = 0; i<=n; i++){
        (*M)[i] = malloc(m*sizeof(double));
        if((*M)[i] == NULL){
            /* free what is allocated before failing */
            for(i--; i>=0; i--) free((*M)[i]);
            free(*M);
            return 0;
        }
    }
    return 1;
}