C++ warning: control reaches end of non-void function - c++

Question

I need help with fixing the program. It is not running. I keep getting the warning control reaches end of non void function. I dont know how to fix it. Please help me. The program is suppose to find the volume or the surface area of a sphere. I get the warning on the last 2 }
#include <iostream>
#include <iomanip>
#include <cmath>
#include <math.h>
using namespace std;
char s = '\0';
const char SENTINEL = 's';
float radius, answer;
void get_radius (float&);
float surface_area (float);
float volume (float);
float cross_section (float);
const float PI = 3.14;
int main()
{
cout << "This program will let you input the radius of a sphere to find its volume or surface area." << endl << endl;
cout << "Enter 'v' for volume or 'a' for surface area of a sphere" << endl;
cout << "'s' to stop" << endl;
cin >> s;
while (s != SENTINEL)
{
get_radius (radius);
if(s == 'V')
{
volume (radius);
}
else if(s == 'A')
{
surface_area (radius);
}
cout << "Enter 'v' for volume or 'a' for surface area of a sphere" << endl;
cout << "'s' to stop" << endl;
cin >> s;
}
system("PAUSE");
return 0;
}
void get_radius (float& radius)
{
cout << "Please enter the radius of the sphere: " << endl;
cin >> radius;
}
float volume (float radius){
float answer;
answer = 4.0/3.0 * PI * pow (radius, 3);
cout << "The volume is: " << answer << endl;
}
float surface_area (float radius){
float answer;
answer = 4.0 * PI * pow(radius, 2);
cout << "The surface area is: " << answer << endl;
}

Answer 1

your function declaration must match what you are returning. You have to make sure you are returning values from functions that are declared that they are returning something.
volume() and surface_area() are printing things with cout but are not returning anything.
float volume (float radius){
float answer;
answer = 4.0/3.0 * PI * pow (radius, 3);
cout << "The volume is: " << answer << endl;
return answer;
}
float surface_area (float radius){
float answer;
answer = 4.0 * PI * pow(radius, 2);
cout << "The surface area is: " << answer << endl;
return answer;
}

Answer 2

When you declare the type of a function, you need to return a value of that type. For example, your function:
float volume (float radius) {}
Needs a return statement returns a value of type float.
If you don't need the function to actually return something, then declare it void to let the compiler know that. In this case:
void volume (float radius)
Just be careful, since void functions must NOT return a value (they can use a bare return statement, though).
Note also that potential paths which skips the return statement can trigger this error. For example, I could have this function:
int veryBadFunction(int flag)
{
if (flag == 1) {
return 1;
}
}
In this case, even though there IS a return statement in the function, it gets skipped any time the value of flag is something other than '1'. This is why the error message is worded control reaches...