Valgrind: Conditional jump or move depends on uninitialised value(s)

Question

Valgrind is giving me Conditional jump or move depends on uninitialised value(s) and Uninitialised value was created by a heap allocation errors on my current code:

    void createMonsters(Game *game) {
       (void) game;

       Creature *nr;

       int x = 0;
       int r = 0;
       int y = 0;
       int check = 0;
       int c = game->opts.numMonsters;
       int nrm=0;


       nr=malloc( sizeof (Creature) * c);


        for(int i=0;i<c;i++){

            game->numMonsters=nrm;
            r = rand()%2;
            x = rand() % game->opts.mapWidth;
            y = rand() % game->opts.mapHeight;
            check=1;

            while(check!=2){
                check = isBlocked(game,x,y);
                if(check==1){
                    x = rand() % game->opts.mapWidth;
                    y = rand() % game->opts.mapHeight;
            }
                else{

                    nr[i].pos.y=y;
                    nr[i].pos.x=x;
                    nr[i].attack=attackPunch;
                    nrm += 1;
                    check=2;
            }
        }

            if(r==0){
                nr[i].name[0] = 'C';
                nr[i].maxhp = 15;
                nr[i].hp = nr[i].maxhp;
                nr[i].sign = 'C';
        }
            else{
                nr[i].name[0] = 'D';
                nr[i].maxhp = 50;
                nr[i].hp = nr[i].maxhp;
                nr[i].sign = 'D';


        }    

            game->monsters=nr;

        }
       game->numMonsters=nrm;
    }


int isBlocked(Game *game, int x, int y)
    {
            (void) game;
            (void) x;
            (void) y;
            if(x>game->opts.mapWidth || y>game->opts.mapHeight){
                return 1;
            }        }

            if(game->numMonsters!=0){                   
            for (unsigned int i = 0; i < game->numMonsters; i++){
                Creature *monst = &game->monsters[i];
                if (monst->pos.x == x && monst->pos.y == y){
                    return 1;
                }}
            }



            if(game->map.tile[y][x]==TILE_OPEN || game->map.tile[y][x]==TILE_ROOM){
                return 0;
            }
            else{
                return 1;
            }

     }

Valgrind points to nr=malloc( sizeof (Creature) * c); So what I'm doing wrong?

    typedef struct creature_st {
        char name[20];  // name of the monster
        char sign;  // character that represents monster on the game display
        Point pos;  // location of the monster
        float hp;  // current hitpoints
        unsigned int maxhp;  // maximum hitpoints
        void (*move)(struct game_st *, struct creature_st *);  // current movement algorithm for monster
        void (*attack)(struct game_st *, struct creature_st *);  // current attack algorithm for monster
    } Creature;

Full valgrind error:

==386== Conditional jump or move depends on uninitialised value(s) ==386==    at 0x4C2C1B8: strlen (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==386==    by 0x403F54: test_createMonsters (test_source.c:179) ==386==    by 0x409377: srunner_run (in /tmc/test/test) ==386==    by 0x4057C9: tmc_run_tests (tmc-check.c:134) ==386==    by 0x405464: main (test_source.c:529) ==386==  Uninitialised value was created by a heap allocation ==386==    at 0x4C28C20: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==386==    by 0x4026C2: createMonsters (monster.c:288) ==386==    by 0x403ADF: test_createMonsters (test_source.c:119) ==386==    by 0x409377: srunner_run (in /tmc/test/test) ==386==    by 0x4057C9: tmc_run_tests (tmc-check.c:134) ==386==    by 0x405464: main (test_source.c:529) ==386== 

    typedef struct game_st {
        Map map;
        unsigned int numMonsters;  // number of elements in 'monsters' array
        Creature *monsters;  // dynamic array of all monsters
        Point position;  // current position of the player
        float hp;  // hit points, should never be higher than 'maxhp'
        unsigned int maxhp;  // maximum hit points
        Options opts;
    } Game;

Answer 1

Uninitialized value has been created somewhere in your code and that function accesses that value. Use --track-origins=yes option to valgrind to track where that value comes from.