Function (int?) that returns pointer in c

Question

I know that i have to define at the beginning of the function what type it is supposed to return, but i dont know how to do it with pointer.. i try to do it like this with int * but its not working

int *sorting(int Num_Gaag, FILE *f) {
  typedef struct {
    int x;
    int y;
    int size;
    float power;
  } gaag;
  gaag *arrgaags;
  int i = 0, j;
  int counter = 0;

  arrgaags = malloc(sizeof(gaag) * Num_Gaag);
  fseek(f, 67, SEEK_SET);
  for (i = 0; i < Num_Gaag; i++)
    fscanf_s(f, "(%d,%d)   \t%d\t%f\n", &arrgaags[i].x, &arrgaags[i].y,
             &arrgaags[i].size, &arrgaags[i].power);
  return *arrgaags;
}

thank you!

You want return a int * or a gaag * ? Your minimal reproducible example is very unclear. — Stargateur
– Stargateur, Commented Jun 14, 2017 at 23:28
It will be difficult to use a gaag* outside of the function if its definition is only visible inside the function, even if you could somehow return it. — aschepler
– aschepler, Commented Jun 14, 2017 at 23:29
You can't return arrgaags if the function returns an int or int *; arrgaags (that sounds like a cry for help!) is a pointer to a structure type that is not accessible outside this function. — Jonathan Leffler
– Jonathan Leffler, Commented Jun 14, 2017 at 23:29

Barmar · Accepted Answer · 2017-06-14 23:34:40Z

2

You need to declare the structure outside the function, then you can return gaag*.

typedef struct {
    int x;
    int y;
    int size;
    float power;
} gaag;

gaag *sorting(int Num_Gaag, FILE *f) {
    gaag *arrgaags;
    int i = 0, j;
    int counter = 0;

    arrgaags = malloc(sizeof(gaag) * Num_Gaag);
    fseek(f, 67, SEEK_SET);
    for (i = 0; i < Num_Gaag; i++)
        fscanf_s(f, "(%d,%d)   \t%d\t%f\n", &arrgaags[i].x, &arrgaags[i].y,
                 &arrgaags[i].size, &arrgaags[i].power);
    return arrgaags;
}

Note that you don't use * when returning the pointer, since that would return just the structure that the pointer points to (the first element of the array).

answered Jun 14, 2017 at 23:34

Barmar

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2 Comments

RoiHatam Over a year ago

But you don't free(arrgaags) it creates a memory leak.

Barmar Over a year ago

The caller has to free it when they're done using the array.

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