how to join a list of strings in c (comma separated). surprisingly worked at the first try

gistfile1.c

char *joinlist(char **list, char *obj, int count)
{
    char *str = NULL;
    size_t total = 0;
    size_t length = 0;
    int i;
    for(i = 0; i < count; i++){
        total += strlen(list[i]);
    }
    total += count - 1;
    str = (char*) malloc(total); //should probably free this sometime
    str[0] = '\0';
    for(i = 0; i < count; i++){
        if(i != count - 1){
            strcat(str, list[i]);
            strcat(str, obj);
        }
        else strcat(str, list[i]);
    }
    return str;
}