Why am I getting "void value not ignored as it ought to be"?

I have the following function :

void getdata(int arr[], int n)
{

    for (int i = 0; i < n; i++) 
    {
        int a = srand(time(NULL));
        arr[i] = a;
    }
}

And I call it in main:

getdata(arr, 1024);

I get "void value not ignored as it ought to be" but I don't understand what is wrong.Why do I get this error?

Solution 1:

  int a = srand(time(NULL));

The prototype for srand is void srand(unsigned int) (provided you included <stdlib.h>).
This means it returns nothing ... but you're using the value it returns (???) to assign, by initialization, to a.

Edit: this is what you need to do:

#include <stdlib.h> /* srand(), rand() */
#include <time.h>   /* time() */

#define ARRAY_SIZE 1024

void getdata(int arr[], int n)
{
    for (int i = 0; i < n; i++)
    {
        arr[i] = rand();
    }
}

int main(void)
{
    int arr[ARRAY_SIZE];
    srand(time(0));
    getdata(arr, ARRAY_SIZE);
    /* ... */
}

Solution 2:

The original poster is quoting a GCC compiler error message, but even by reading this thread, it's not clear that the error message is properly addressed - except by @pmg's answer. (+1, btw)

error: void value not ignored as it ought to be

This is a GCC error message that means the return-value of a function is 'void', but that you are trying to assign it to a non-void variable.

Example:

void myFunction()
{
   //...stuff...
}

int main()
{
   int myInt = myFunction(); //Compile error!

    return 0;
}

You aren't allowed to assign void to integers, or any other type.

In the OP's situation:

int a = srand(time(NULL));

...is not allowed. srand(), according to the documentation, returns void.

This question is a duplicate of:

error: void value not ignored as it ought to be
"void value not ignored as it ought to be" - Qt/C++
GCC C compile error, void value not ignored as it ought to be

I am responding, despite it being duplicates, because this is the top result on Google for this error message. Because this thread is the top result, it's important that this thread gives a succinct, clear, and easily findable result.

Why am I getting "void value not ignored as it ought to be"?

Solution 1:

Solution 2:

error: void value not ignored as it ought to be

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