Infinite loop at compile time?

Question

Is it possible to enter an infinite loop at compile time?

My program seems to enter an infinite loop when I attempt to compile it. I have a class with a class constructor that calls the method gameRun(). gameRun() calls itself at the end of its execution, but should have the appropriate checks to be able to break from it during run time... However when I attempt to compile the class, I actually seem to get an infinite loop then.

My understanding of compilation is that it does not actually execute the code... Which would mean it would be impossible to enter an infinite loop unless there is actually a serious bug in the compiler's source. Is this correct?

I am writing in Java, and am using BlueJ (a beginner's IDE which I am growing out of) as my IDE.

Thanks in advance.

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Thanks to you all for so many helpful responses. Just thought I'd post an update, as this seems to have perked some interest, and I am curious about it myself.

I have not done a whole lot with BlueJ or this error since I posted the original error, becuase I had taken the source files from the project, and was able to successfully compile and run them with eclipse. This suggests to me that it is a BlueJ (or related) problem. I have continued to work on this project with eclipse without any more problems of this nature. I will follow up with more detail on the problem when I am able to use the machine with the original project on it again. (Nothing should have been changed since)

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As an afterthought... Is there any way I can link this question to an account I have created and registered since this was posted? I can't find a way to do that, and it would make keeping track of this more convenient...

Answer 1

Some languages do allow the compiler to enter an infinite loop. Java isn't one of those languages. :-)

Answer 2

Does your compilation hang (loop) if you just use javac ?

I've never seen a compilation hang indefinitely whilst compiling Java and I'm wondering if BlueJ is having a problem instead.

Answer 3

If BlueJ does use its own compiler, you may have found a bug in it, or in BlueJ's build tools that surround it.

You might take a BinaryChop approach to this one: break your program into pieces, compile them individually, and see if the compiler-hanging behavior can be isolated to a small, specific testcase. At the end of the day, you'll either have an excellent bug report to show the BlueJ people, or you'll find that your program actually does compile (yet you'll be scratching your head).

Answer 4

AFAIK, Standard Java cannot be compiled infinitely.

Are you sure that the problem is at compilation rather than at some other feature that BlueJ provides? Many Eclipse-based IDEs perform multiple actions during a rebuild, and that compilation is just one of them. It is possible that something else does.

What exactly do you see? An unending Eclipse task?

Answer 5

It would be theoretically possible to do if, for example, to compile a file, the compiler first had to have finished compiling that file. (Ahhh... Recursion). But I'd imagine checking for that kind of madness would be the first thing a real-world compiler would handle.

But I wouldn't think it would happen on a method/function, unless (postulating) the compiler was trying to resolve tail-recursion to an simpler implementation, and failing. But, again I can't imagine that would be an issue with a modern Java compiler, even if it exists at all. Certainly I'd imagine that the compiler would eventually give up and post an error rather than infinite looping.

It's far more likely to be the IDE than the compiler. At a guess, the IDE might be trying to trace a warning/error to its source in the code in order to highlight it and getting trapped. Does BlueJ have text-highlighting on compiler errors/warnings? You could try turning it off.

Although, as many others have already suggested, the first real test is to compile from the command line using

javac *.java

Or whatever files your code uses.

EDIT: Sorry I never got back to you. For future reference, to compile from the command line (I'm assuming Windows as your OS):

1. Open the command line by going to the start menu and select Run...
2. Type cmd into the Run dialogue, and click OK.
3. This should bring up a cmd.exe console.
4. From here, use the "cd" command to change directory to the directory containing your java files. (cd "My Documents\Java\Monster Battle\core")
5. Once you're in the right directory, type "javac *.java". This will run the compiler without needing to deal with the IDE. It should pause while compiling, and when it's done, you get the command prompt back.
6. If you type "javac *.java -verbose" you get full output, in case you get your infinite loop.

If that works fine, it's an IDE bug. Send them a bug report. If it doesn't, congratulations! You've found something really interesting, that will probably tie up some poor Sun developer for a month.

Answer 6

Try to make the source code you are compiling as small as possible and still exhibit the behaviour you describe. The process of doing so, may help you identify what the problem is.