Returning value from Void Function

if you are not satisfied with the answer of Alber Holguin, just see this example.
The following example show you how to retrieve value from void type function. int *p, here pass a variable from main() function and that variable will be changed inside fun() function.
It calls pass value by reference.

#include<stdio.h>
#include<conio.h>
void fun(int *p);/* function prototype */
int main()
{
 clrscr();
 int x=0;
 fun(&x); /* function call*/
 printf("%d",x);
 getch();
return 0;
}
void fun(int *p) /*function body/definition*/
{
 *p=13;/*any int value*/
}

In addition to the other answers, which are technically correct: if your really need to return something, using a void function makes no sense at all. After all, what is the return parameter for?!

I would somehow understand if you already have one return parameter and then need to add something else to return. The answer would be 1) return second value using a parameter by reference; 2) using pointer passed by value and changing the pointed object in the code of your function (as it is done on C); 3) using return parameter, but with a different type such as class or struct, so all your return data would be passed in the members of the class/struct.

But no, you're asking about returning something from a void function. This is really an oxymoron. In practice, there is no situation when it can be needed.

[EDIT]

Example:

//makes no sense:
void func1(int &value){ value = some_value; }

//how it should be:
int func1(){ return some_value; }

Same thing with any other parameter type. With reference or pointer type a caution should be used: the object should exist even when an instance of the class is destroyed, but this is exactly same thing as with passing the our parameter by reference. Read also on the concept of l-value in any C++ manual.

[END EDIT]

—SA

In addition to above valuable answers, cheating a little bit. :-)

void voidFunc(const int nVal)
{
    int nRet = nVal + 8;
#ifdef __GNUC__	
    asm("movl %0, %%eax"
        : 
        : "r"(nRet)
        : "%eax"
       );
#else
    _asm mov eax, nRet
#endif
}

int main(void)
{
    int nRet = 0;
    voidFunc(10);

#ifdef __GNUC__	
    asm("movl %%eax, %0"
        :"=r"(nRet)
        :
        :"%eax"
       );
#else
    _asm mov nRet, eax
#endif

    printf("Result is %d\n", nRet);

    return 0;
}

Disclaimer:
This is not a competitor solution, and is also "as is".