Question

I get this Valgrind output (that’s the only error I get):

==20627== Conditional jump or move depends on uninitialised value(s)
==20627==    at 0x804913A: main (main.c:223)

My main.c roughly looks like this:

//other code

char **sets;

//other code

//char** get_char_sets(FILE *source);
sets = get_char_sets(config_file); // I malloc the sets in here

//other code

int i = 0;
while(sets[i]){ // line 223
    free(sets[i]);
    i++;
}
free(sets);

//other code

get_char_sets looks like this:

char** get_char_sets(FILE *source){

    char **sets = malloc((n + 1) * sizeof(char*));

    for(int i=0;i<=n;i++){
        sets[i] = malloc(1 * sizeof(char));
    }

    //rest of function

    return sets;
}

I understand that valgrind says that i’m working with an uninitialized variable, the only one I can possibly see is sets, but it gets malloc()ed in get_char_sets() and than assigned with the returned pointer.

How can I get rid of that valgrind error in order to correct my code?

Answer 1

There is no limit on the value of i, which will eventually result in out of bounds:

while(sets[i]){

Change to (something like):

int i = 0;
while(i <= n && sets[i]){ /* Ensure check i <= n before accessing sets */
    free(sets[i]);
    i++;
}
free(sets);

You could also add a NULL sentinel value into sets and the while as is would be fine.