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Search - "undefined behavior"
LONG RANT AHEAD!
In my workplace (dev company) I am the only dev using Linux on my workstation. I joined project XX, a senior dev onboarded me. Downloaded the code, built the source, launched the app,.. BAM - an exception in catalina.out. ORM framework failed to map something.
mvn clean && mvn install
same thing happens again. I address this incident to sr dev and response is "well.... it works on my machine and has worked for all other devs. It must be your environment issue. Prolly linux is to blame?" So I spend another hour trying to dig up the bug. Narrowed it down to a single datamodel with ORM mapping annotation looking somewhat off. Fixed it.
mvn clean && mvn install
the app now works perfectly. Apparently this bug has been in the codebase for years and Windows used to mask it somehow w/o throwing an exception. God knows what undefined behaviour was happening in the background...
Months fly by and I'm invited to join another project. Sounds really cool! I get accesses, checkout the code, build it (after crossing the hell of VPNs on Linux). Run component 1/4 -- all goocy. run component 2,3/4 -- looks perfect. Run component 4/4 -- BAM: LinkageError. Turns out there is something wrong with OSGi dependencies as ClassLoader attempts to load the same class twice, from 2 different sources. Coworkers with Windows and MACs have never seen this kind of exception and lead dev replies with "I think you should use a normal environment for work rather than playing with your Linux". Wtf... It's java. Every env is "normal env" for JVM! I do some digging. One day passes by.. second one.. third.. the weekend.. The next Friday comes and I still haven't succeeded to launch component #4. Eventually I give up (since I cannot charge a client for a week I spent trying to set up my env) and walk away from that project. Ever since this LinkageError was always in my mind, for some reason I could not let it go. It was driving me CRAZY! So half a year passes by and one of the project devs gets a new MB pro. 2 days later I get a PM: "umm.. were you the one who used to get LinkageError while starting component #4 up?". You guys have NO IDEA how happy his message made me. I mean... I was frickin HIGH: all smiling, singing, even dancing behind my desk!! Apparently the guy had the same problem I did. Except he was familiar with the project quite well. It took 3 more days for him to figure out what was wrong and fix it. And it indeed was an error in the project -- not my "abnormal Linux env"! And again for some hell knows what reason Windows was masking a mistake in the codebase and not popping an error where it must have popped. Linux on the other hand found the error and crashed the app immediatelly so the product would not be shipped with God knows what bugs...
I do not mean to bring up a flame war or smth, but It's obvious I've kind of saved 2 projects from "undefined magical behaviour" by just using Linux. I guess what I really wanted to say is that no matter how good dev you are, whether you are a sr, lead or chief dev, if your coworker (let it be another sr or a jr dev) says he gets an error and YOU cannot figure out what the heck is wrong, you should not blame the dev or an environment w/o knowing it for a fact. If something is not working - figure out the WHATs and WHYs first. Analyze, compare data to other envs,... Not only you will help a new guy to join your team but also you'll learn something new. And in some cases something crucial, e.g. a serious messup in the codebase.11
StackOverflow: let's marginalize your "problem" and focus on the real issue at hand, which is that line 4 doesn't conform to the language standards and thus will lead to undefined behavior on a single kind of 8-bit microcontroller made in 1984 that is no longer in use.5
I love Linux, but its community can be so full of incompetent assholes..
Just now I asked in Freenode ##linux how to get the process ID of my current running process in bash. I got my answer - it's a shell built-in called "$$".
Then people start to nitpick some more - why do you need it? How is that different from an exit? - to which my response was.. well I know the whole idea behind exit codes, and I'd use it whenever possible, in all defined behavior that allows my program to terminate itself whenever it can. This pidfile however would be used to exit itself and provide diagnostic information whenever the program enters undefined behavior - a segfault in C language. Scenarios in which I don't have full control over the script's behavior anymore, such as the system entering an unworkable state where the system stalled, still got some binaries in RAM but the rootfs got unwritable, such as now - very helpfully, thanks HP! - when my laptop likely overheated and shat itself. I issued sudo reboot into it, but even that wouldn't issue properly anymore due to the /sbin/poweroff binary becoming inaccessible too. I had to issue a hard power cycle.. one of the few times in which I'm thankful to HP for actually causing shit like this, lol.
Point is, that undefined behavior is what I'm trying to mitigate against. I certainly can't let any files other than diagnostics remain in nonvolatile storage like that, especially when their state should be predictable in order to ensure good operation (like files expressing whether the script is already running or not, i.e. lock files).
Back to that IRC chat. Aside from the answer, I got ridicule from people who probably don't even know how to properly compile a kernel. Ubuntu users, overconfident scum. Sometimes I feel like I should ask questions in channels like #archlinux only, where such incompetency is ridiculed on its own.14
The GashlyCode Tinies
A is for Amy whose malloc was one byte short
B is for Basil who used a quadratic sort
C is for Chuck who checked floats for equality
D is for Desmond who double-freed memory
E is for Ed whose exceptions weren’t handled
F is for Franny whose stack pointers dangled
G is for Glenda whose reads and writes raced
H is for Hans who forgot the base case
I is for Ivan who did not initialize
J is for Jenny who did not know Least Surprise
K is for Kate whose inheritance depth might shock
L is for Larry who never released a lock
M is for Meg who used negatives as unsigned
N is for Ned with behavior left undefined
O is for Olive whose index was off by one
P is for Pat who ignored buffer overrun
Q is for Quentin whose numbers had overflows
R is for Rhoda whose code made the rep exposed
S is for Sam who skipped retesting after wait()
T is for Tom who lacked TCP_NODELAY
U is for Una whose functions were most verbose
V is for Vic who subtracted when floats were close
W is for Winnie who aliased arguments
X is for Xerxes who thought type casts made good sense
Y is for Yorick whose interface was too wide
Z is for Zack in whose code nulls were often spied
- Andrew Myers6
I read this in stackoverflow today:
Welcome to every C/C++ programmers bestest friend: Undefined Behavior.
There is a lot that is not specified by the language standard, for a variety of reasons. This is one of them.
In general, whenever you encounter undefined behavior, anything might happen. The application may crash, it may freeze, it may eject your CD-ROM drive or make demons come out of your nose. It may format your harddrive or email all your porn to your grandmother.
Ever wanted to have undefined behavior in Python? Do this in Python 2 (yes this was supposed to be a fibonacci number calculator with a limit but one of my classmates forgot the conversion just as seen below):
OKAY WHAT THE FUCK JAVA.
At school we were assigned the task to do Huffman's algorithm. Since I am way ahead of all the others, I made a GUI for that. (Btw, we use BlueJ for Java, it's just painful)
Now... I made a JTextField to put the output, which would be any character from 0x0 to 0xFFFF, into it.
Apparently, there is a bug in the setText method, which throws random NullPointerExceptions right into your face if you give it those Unicode characters.
So I looked it up:
It was a Bug, in JDK 1.6.something, where putting a 0xFFFF together with a 0x10000 would cause this. Now you may think, do we still have 1.6? No, we have 1.8 v171, WHY THE FUCK DOES THIS SHIT GIVE ME A NPE?! THE WORST PART IS I CAN'T DO ANYTHING ABOUT IT!
AND IT HAS THE WORST UNDEFINED BEHAVIOR:
1. NPE, nothing else happens
2. The Text box just gets invisible, but the border stays visible + NPE
3. The box completely disappears + NPE
Try-catching it doesn't do anything, everytime I fill the box with text, one of those options happens, and the box was never to be seen again! NOT EVEN CREATING A NEW TEXT BOX AND ADDING IT TO MY WINDOW WORKS.12