Question

Here is my code:

int main(void)
{
    int i;
    Coords** latLng;
    Quadrado* q1;
    latLng[0] = AdicionaValores(latLng[0],-23.000490,-43.346687);
    latLng[1] = AdicionaValores(latLng[1],-22.988243,-43.342224);
    q1 = AdicionaValoresQuadrado(q1,-23.000490,-43.346687,-22.988243,-43.342224);

    printf("# Connecting to database.\n");
    for(i=0;i<2;i++)
    {
    if(clientInside(q1, latLng[i]))
        printf("Dentro");
    else
        printf("Fora");
    }
    system("PAUSE");
}

Here is AdicionaValores and AdicionaValoresQuadrado:

Coords* AdicionaValores(Coords* v, double x, double y)
{
    v = (Coords*) malloc(sizeof(Coords));
    v->x = x;
    v->y = y;
    return v;
}

Quadrado* AdicionaValoresQuadrado(Quadrado* q, double x1, double y1, double x2, double y2)
{
    q = (Quadrado*) malloc(sizeof(Quadrado));
    q->x1 = x1;
    q->x2 = x2;
    q->y1 = y1;
    q->y2 = y2;
    return q;
}

it compiles just fine with 2 warnings, telling me that latLng and q1 are uninitialized! what should I do ?? malloc them on main ? help!

Answer 1

latLng and q1 are indeed uninitialized.

Coords** latLng;
latLng[0] = …

You’ve never assigned anything to latLng, and yet you try to treat it as a pointer to an array where you want to put a value. You need not only to initialize latLng to a valid pointer, but also allocate memory for the array. Since this is an array with a fixed size (2) which doesn’t need to last beyond the lifetime of the function, you can allocate it on the stack.

Coords* latLng[2];
latLng[0] = …

After that change, you’ll still get warnings about uninitialized variables, but this is due to a problem in the interface of AdicionaValores and AdicionaValoresQuadrado. These functions never actually use their first argument, but they require one, and you’re passing a completely arbitrary value. Just remove the first argument, and declare v as a local variable.

Coords* AdicionaValores(double x, double y)
{
    Coords *v = malloc(sizeof(Coords));
    v->x = x;
    v->y = y;
    return v;
}

(Note that you don’t need to cast the return value of malloc, and you should never use a cast unless you have a reason to and you understand why. In a production program, you should check if malloc runs out of memory, but that’s ok for now.) Then in main:

Coords* latLng[2];
Quadrado* q1;
latLng[0] = AdicionaValores(-23.000490,-43.346687);
latLng[1] = AdicionaValores(-22.988243,-43.342224);
q1 = AdicionaValoresQuadrado(-23.000490,-43.346687,-22.988243,-43.342224);