Stupidest Programming Mistakes

[Tom Bottiglieri]

Ehem...

http://www.firstwiki.org/media/2/2e/RobotAttack.avi

[Donut]

This is easily the worst mistake made this year.

Else (current_state == enabled && last_state == disabled)

It took us 3 hours of staring at it to realise you can't put conditions on an else.

[Andrew Blair]

Last night, tried to get my drive code lookup table to compile. Turns out that I did everything right...except NAME THE STUPID THING!!! Thanks to Alan Anderson for catching it.

[aaeamdar]

Originally Posted by Andrew Blair

Last night, tried to get my drive code lookup table to compile. Turns out that I did everything right...except NAME THE STUPID THING!!! Thanks to Alan Anderson for catching it.

Gosh that is funny. When programming in java I've gotten so lost in

public static final volatile private blah

that I forgot to give it an actual type. I did this:

public static final theta;

It no like that...

Good thread.

Paul Dennis

[ForgottenSalad]

Originally Posted by Tom Bottiglieri

Ehem...

http://www.firstwiki.org/media/2/2e/RobotAttack.avi

That's why you don't use the screws on the serial cable.

[6600gt]

if(joyin - pwmout > rate)
pwmout = pwmout + rate;

joyin - pwmout could be negative but they were all unsigned variables so it never looked at nagatives. So for example it would still execute when (-10 > 5)

Took 2 hours to realize that!

[Mike]

I won't mention the hundreds times I've forgotten a semicolon, I'm sure that's all too common.

So I'll mention the time I was debugging a version of code and wondering why the printf's weren't working. Turns out I was downloading the old (buggy) version of the code

[theycallhimtom]

Working on code for a few days working through all the bugs. Then when it coms time to use it a few weeks later I have lost the code and have forgotten how I fixed all the problems I came across. So I had to redo the code and attempt to remeber how I dealt with each error.

Also assuming that ints were 32 bit caused me some pain.

Oh and almost every day when I download code to the robot I download from the wrong project and realize it a few mins later when the printfs are all wrong.

[Eldarion]

One of the things that keeps tripping us up is that the MPLAB compiler does not follow standard C data type promotion rules.

For example, given the statement below, standard C would promote both data types to integer, then multiply. The MPLAB compiler, however, multiplies a and b as unsigned chars and then sticks the result in the integer value, resulting in an overflow where you least expect it!

unsigned char a = 127:
unsigned char b = 127;
int result;

result = (a * b);

[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.