Stupidest Programming Mistakes

[seg9585]

We've had QUITE a few:

to convert angle radians to degrees:

int tiltdeg = tiltrad*( (int)3.14 / 180 );

hmmm, no wonder why we kept getting "0" as a tile angle...
and oh yeah, it shoulda been 180/3.14 to begin with...


In trying to comment stuff out with "/* */", we realize that we comment out other stuff already commented out using the same method, and whenever it reached that comment's "*/" it would end, causing a bunch of syntax errors throughout the rest of the uncommented code, and we couldnt figure out for the life of us why it was reading that code...

and dont know what we were thinking here:

if(TILT_SERVO > Tilt_Servo_Max)
TILT_SERVO = Tilt_Servo_Max - Tilt_Servo_Min + Step_Size;

um, I think we were trying to have the camera search in the last area it saw the light if it immediately loses it too high...but um.. Tilt_Servo_Min = 0 and Step_Size is greater than 0...

[Matt Krass]

Originally Posted by seg9585

In trying to comment stuff out with "/* */", we realize that we comment out other stuff already commented out using the same method, and whenever it reached that comment's "*/" it would end, causing a bunch of syntax errors throughout the rest of the uncommented code, and we couldnt figure out for the life of us why it was reading that code...

Little trick Mark McLeod showed me for that:

#ifdef //This is actually a comment block, #1
code
code
code
#endif //This is the end of comment block #1

Since the #ifdef is missing something to check, it always fails, so any code in it never compiles, doesn't get stopped by */, quite useful

[Mike Shaul]

The C Programing language has MANY different "issues" with undefined behavior or easy-to-make mistakes that compilers won't usually catch.

This website has compiled 10 (actually more than 10) common mistakes, check it out.

[Goldeye]

My teammate made a great slipup that him and a mentor didn't catch till I looked. Here it is (with the error) in a function for averaging something in pseudocode.

int sum,count;
while(stuff_left)
{
     sum+=stuff;
     count++;
}
if(!count == 0)
     return -1
else
     return sum/count;

[Cuog]

I havent made any hilariously dumb mistakes coding, i have done the condition after the else statement but i caught it quickly and i have also done the good old no semi-colon, but my most hilarious story is from an alumni from our team on his first programming attempt,

Basically to init his PWM values he set them to 0 logically thinking that zero meant no speed, the robot the ran full speed backward over the laptop he was using to program giving it the name "smokey" for ever and now i have to try and fix this old i286 laptop to use for some random off season stuff

[Kristian Calhoun]

this was one that someone els eon our programming team made that i had caught. we kept trying to compile the code and we kept getting an error, it ended up that instead of pwm01 and pwm02, that the other member of our team had put pwn01 and pwn02. we reached the conclusion that you cannot pwn the pwms lol.

[scitobor 617]

For some reason whenever I open a project in MPlab it automaticlly opens user_routines.c from an old version of my code. It took me half of a saturday to figure out way changing stuff in user_routines.c had no effect what so ever, even when I intentionally added errors that should have caused all kinds of compile time errors. I still do not know what is causing this but I now know to check which file I'm editting before I make any changes.

[BrianR]

Today we were trying to do our angle calculations, and we had made a trig mistake. So we changed it and uploaded the code. But for some reason it kept having the same problem. After we changed some other stuff to no result, we happened to notice that the loader was calling the wrong code, and that for some reason, it had built the .hex file to a different spot. Once we figured that out, it worked like a charm.

[Chris_Elston]

    if (varible = 1)
    {
      do this;
    }

Burns me ALL this time....don't forget to use DOUBLE equal signs....

[tpc]

Originally Posted by chakorules

Burns me ALL this time....don't forget to use DOUBLE equal signs....

This is why I always write the constant first, when comparing equality between a constant and a variable:

if (1 == variable)
{
  /* do something */
}

Then if I inadvertently use an assignment rather than a comparison, it's a compile-time error (can't assign a value to a constant).

[ForgottenSalad]

I spent an hour and a half or so trying to figure out why a new revision of our code wasn't working at all today. After switching speed controllers, cables, checking for abnormalities with a multimeter... I realized I had never called my routine. I ended up (stupidly) slamming my fist down on the laptop.

[Chris_Elston]

This is an EXCELLENT idea. Thanks for sharing this.

Originally Posted by tpc

This is why I always write the constant first, when comparing equality between a constant and a variable:

if (1 == variable)
{
  /* do something */
}

Then if I inadvertently use an assignment rather than a comparison, it's a compile-time error (can't assign a value to a constant).

[X-Istence]

Listen to the compiler when it tells you about casting. Don't try to force something to cast, and then lose information. Like going from unsigned to signed ints.

[jfelser]

I dunno if this is truly a programming mistake... but testing autonomous (using PID) we forgot to plug in one of the the interrupt pins on the encoders, resulting in a very interesting open-loop control system, and various material damages (the robot LED, the green light, the 6' stack of books the light was sitting on, the desk the books were sitting on, the counter with microscopes behind the desk with the books and light, and my self confidence).

[aaeamdar]

I had this:

auto_mode = ~auto_select1 + 2(~auto_select2) + 3(~auto_select3);

Where auto_mode is later used in a switch{case:}, and auto_selectNs are variouss rc_dig_ins.

Can someone spot the error there? Yeah, 2() is not a valid method. So I changed it to this:

auto_mode = ~auto_select1 + 2*(~auto_select2) + 3*(~auto_select3);

And it still didn't work. Gee whiz. What is wrong now. It gives me a run-time unexpectedness glitch where auto_mode is calculated to be 246 or some nonsense like that. OK, fixed that by not using the binary complement and instead used the logical complement (in a #define) and it works.

In another one we had:

printf("Some motor values %d %d %d", 1,2,3);//Whatever

And nothing was printing. Gosh, that sure was weird. Well, it turns out that we failed to import stdio.h (or anything else that gives us access to printfs). And then, to make things worse, the C language is so incredibly stupid that all it gives you is a warning because it's not prototyped. Since we had been using some other methods that weren't prototyped (may have been a few in Kevins Code) those warnings got mushed in with the others.

Thank goodness for Java.

Paul Dennis