Why doesnt my function count? - c++

Question

I have a function that if you plug a number into it it counts them out. It only does this if you call the function at the begining of the program meaning it has something to do with clock(). I added clock() to the rest of my variables but the function doesnt count. Specifically at the if statement.
code:
#include <stdio.h>
#include <string>
#include <iostream>
#include <stdlib.h>
#include <windows.h>
#include "math.h"
#include <time.h>
#include <ctime>
#include <cstdlib>
#include <mmsystem.h>
void countbysec(int Seconds);
using namespace std;
int main(){
int secondsinput;
cout<<"Type how many seconds to cout \n";
cin>>secondsinput;
countbysec(secondsinput);
return 0;
}
void countbysec(int Seconds){
clock_t Timer;
Timer = clock() + Seconds * CLOCKS_PER_SEC ;
clock_t counttime = clock() + (Timer / Seconds);
clock_t secondcount = 0;
while(clock() <= Timer){
if(clock() == counttime){
counttime = counttime + CLOCKS_PER_SEC;
secondcount = secondcount + 1;
cout<<secondcount<<endl;
}
}
}

Answer 1

You're not calling the function with this line:
void countbysec(int Seconds);
You're forward declaring the function. The compiler needs to see the declaration of the function before you can call it otherwise you'll see:
error: use of undeclared identifier 'countbysec'
It needs to be able to type check and generate the code for the call at the point you make the call.
You could declare and define the function in one step by moving the code block from below main() to above it in your file. This is normal C/C++ behaviour.

Answer 2

First, clock is not the right tool to do what it looks like you want. It returns an approximation of how much CPU time has been used by the process. Approximation should have a few alarm bells ringing. Next, time CPU time is not the same as wall time, so who can say just how much elapsed time went by while the program worked its way to ten seconds.
So
if(clock() == counttime){
The time must be EXACTLY counttime in order to do your count-incrementing. The odds of pulling this off are not too good. You might shoot past it. And if you do, nothing will ever be counted. I recommend
if(clock() >= counttime){
Next, you are unlikely to get that last second because
while(clock() <= Timer)
Probably trips first and exits the loop.
If you want to count seconds, look to something like std::this_thread::sleep_until.
Set Wake time = current time + 1 second, then
Sleep until Wake time,
count,
Add a second onto Wake time,
repeat until done.