Debugging

So while the thief game under goes some planning, I decided to finish up an old script I had from back in the A5 days, a silly game called "TANKS!"

Well, the game's programming is really simple and a good amount of it has been scripted, it just isn't in Lite-C yet.

And there I was trying to get a health bar to show up on the screen. The way a health bar works is that it's size_x (horizontal size) is affected by a percentage of the players health. So to get this percent, I defined a skill and called it "maxHealth." MaxHealth defaults (allegedly) at 100. The code looked like this:

#define distDown skill6
#define bottom skill7
#define maxHealth skill8

//..more variables and other things that do not affect maxHealth

action pTank()
{
 var engSnd;
 wait(1);                //wait for the first frame for c_setminmax
 c_setminmax(me);             //set the bounding box
 set(my,FLAG2 | SHADOW | CAST | METAL);      //set some flags
 player = my;              //set the point
 my.health = 100;             //set health to the default 100
 my.maxHealth = 100;
 turret = ent_create("tankturret.mdl",my.x,pTurret);
        //... code continues, does not use my.maxHealth after this


function initScreen()
{
 while(!player) { wait(1); }     //wait for the player to be loaded
 set(healthBar,VISIBLE | LIGHT);    //turn on the health bar and allow it to be set by RGB values
 vec_set(healthBar.blue,vector(0,200,0)); //health bar is green
 while(player)          //while the player exists
 {
  healthBar.size_x = 190 * (player.health / player.maxHealth);
  wait(1);
 }
}

function initScreen() sets up the GUI and places a health bar where you can see the part divided by total formula being used to make the healthBar.size_x proportional to the player's health.

After putting this together, I got an empty pointer crash. After I fixed that with a wait(1) instruction, everything was great and dandy, except the healthBar was not showing up on my screen.

So I thought maybe the while condition is for some reason not true. I stuck "beep()" in initScreen in several places and did several test runs. What beep() does is it plays a sound so it is an easy way to test code.

They beeped.

I thought maybe something somewhere is setting the VISIBLE flag on the healthBar off. I wrote a quick function:

if(is(healthbar,VISIBLE))
{
     beep();
}

It beeped. I had a health bar that was visible. Its flags were correct, in fact, the flags were the same exact flags as I have set on a health bar in a different project, a health bar that works. The while conditions were good. There was no reason why the bar wasn't showing up. None.

And then I thought, maybe its the equation itself, the "healthBar.size_x = 190 * (player.health / player.maxHealth);"

I used diag_var() in here to get the engine to write down what the size was.

And what I got astonished me.

-317.

The scale was a negative number. Then I looked at player.health.

The diagnostic spit 100 at me.

Then I looked at player.maxHealth

The diagnostic spit a negative number that made no sense.

Looking at the code I posted at the beginning of this post, I could not see what it was. player.maxHealth was set to 100 and that was the only place where I set it equal to anything. There was no other point in the script where it was used.

So I decided to try a global variable rather than a skill. I called it "pMaxHealth." I set that to 100 and put it in place of "player.maxHealth" in function initScreen().

And the bar worked.

And then it hit me.

I looked at skill7, above player.maxHealth, the one called "bottom."

Bottom is used here:

vec_for_min(my.bottom,me);

That one line of code finds the bottom of an object and returns a vector. my.bottom was now a vector. In 3D graphics, vectors have 3 parts, x,y,z. If you define a skill and use it as a vector, the following two consecutive skills become the y and z components. skill7, bottom, was a vector, and thus skill8 and skill9 were parts of that vector. And so maxHealth, which was skill8, was in fact being modified by the vec_for_min instruction, which came after its assignment of "player.maxHealth = 100;"

So the whole issue was fixed by changing maxHealth to skill 11.

I guess breakpoint was a good name for this blog. There are so many things that can go wrong.

while(thisCodeDoesntWork)
{
   smashComputer();  //take out some pent out anger
   throwDartsAtBoss();  //take out more anger
   sleep(6*60*60);  //sleep six hours
}