New Linux Timing Code
For some time, I had a problem with my old Linux timing code. The units hr_time.h/c had to have the includes arranged in the right order and some flags set for it to compile. Plus it never seemed right having to do this in hr_time.h
#include <linux/time.h>
#define __timespec_defined 1
#define __itimerspec_defined 1
#define __timeval_defined 1
But today I found some better code on this SolarianProgrammer website and I’m always happy to give credit where it’s due. I’ve witched to using C17 which clang on Ubuntu (clang 14) and Raspberry Pi (clang 11) both seem to accept.
So now my hr_time.h looks like this:
hr_time.h
#pragma once
#include <stdlib.h>
#include <time.h>
void startTimer();
void stopTimer();
double diff();hr_time.c
#include "hr_time.h"
#include <time.h>
#include <stdlib.h>
#include <stdio.h>
struct timespec start;
struct timespec end;
void startTimer() {
if (timespec_get(&start, TIME_UTC) != TIME_UTC) {
printf("Error in calling timespec_get\n");
exit(EXIT_FAILURE);
}
};
void stopTimer() {
if (timespec_get(&end, TIME_UTC) != TIME_UTC) {
printf("Error in calling timespec_get\n");
exit(EXIT_FAILURE);
}
};
double diff()
{
return (double)(end.tv_sec - start.tv_sec) +
((double)(end.tv_nsec - start.tv_nsec) / 1000000000L);
}I’m only ever using one timer, if you want to modify this to pass in a timer in the startTimer and stopTimer then it’s easy enough.
Both gcc and clang support extensions to C and while i normally try and make things I write about work on Windows (i.e. Visual Studio), these are useful enough that I thought they deserve a mention. Yes I know you can run gcc/clang on Windows using Cygwin or MinGW, but for various reasons I prefer Visual Studio.
I got my Pi 4 a week ago and have been doing experiments on it with my Asteroids game. If I disable the line of code that kills the player ship in the DestroyObject() function and just add a return after case tPlayer: and uncomment the code that adds Asteroids when you press A then I can have lots of asteroids on screen. Also set the MAXASTEROIDS #define to 128.
Silly me completely forgot that Raspberry Pis have a different CPU architecture compared to my PC. You just get used to something working on Linux and it was only after copying and it didn’t run that I realised my mistake. So I now have to recompile Asteroids (from 
Microsoft don’t do an official version for Raspberry-Pi or other ARM boards. However I discovered that a developer called Jay Rodgers has taken their source code (VS Code is open source) and you can get a version 
Clang is very easy to install. Open a terminal and issue this command:
I originally created Asteroids for Windows using Visual Studio 2017 Community Edition. Since then I’ve started the Clang version on Ubuntu and there haven’t been too many differences but there are just a few so in this post I’ll list what I’ve found so far.
Without these, I’d get compile errors like __timespec redefined errors.