Function with array of return type in C

Question

I have the following function in C:

int[] function(int a){
    int * var = (int*)malloc(sizeof(int)*tags);
    ....
}

*varis a pointer to an array var?

If so, how do I return an array ( var) to a function?

Answer 1

You cannot return an array from a function, but a pointer:

int * function(int a){
    int * var = malloc(sizeof(int)*tags);
    //....
    return var;
}

Answer 2

This code below may clarify a bit how arrays and pointers work. The function will allocate memory for the "tags" of int variables, then initialize each element with a number and return a memory segment that points to an array. From the main function, we will cyclically print an array element, then we will free up unnecessary memory.

#include <stdio.h>
#include <stdlib.h>

int *function(unsigned int tags) {
        int i;
        int *var = malloc(sizeof(int)*tags);

        for (i=0; i < tags; i++) {
                var[i] = i;
        }

        return var;
}

int main() {
        int *x;
        int i;

        x = function(10);
        for (i=0; i < 10; i++) {
                printf("TEST: %i\n", x[i]);
        }

        free(x); x=NULL;

        return 0;
}

Answer 3

:

int* function(int tags){ 
  int * var = malloc(sizeof(int)*tags); 
  //.... 
  return var;
} 

( ) C/++, , .

: a, tags . ,

, free() , function , , . malloc tags int s, int var[tags];

UPDATE: malloc return

Answer 4

C . int:

int *function(int a)
{
  int *var = malloc(sizeof *var * tags); // where is tags defined?
                                         // are you sure you don't mean a here?
  ...
  return var;
}

, tags integer var. , var int, int. , .

, , :

int a = ...;
int *arr = function(a);
...
arr[0] = 0;
arr[1] = 1;
...

arr - , , sizeof arr , , (- , ).

Answer 5

C , . , char [] char *

Remember to keep track of the size of the array, also I noticed that tags seem to be a global variable, most of the time it is a good idea to avoid global variables

Here is a sample code:

#include <stdio.h>
#include <stdlib.h>

int* foo(size_t arrSize){
   int* arr = (int*) malloc(sizeof(int)*arrSize);
   return arr;
}


int main (int argc, char** argv){
   printf("Printing array:\n");
   int* arr = foo(42);
   for(int i=0; i <42; i++){
      arr[i]=i;
   }

   for (int i=0; i < 42; i++){
      printf("Element: %d: %d\n", i, arr[i]);
   }
   free(arr);
   return 0;
}