My Xcode speed has come down to a crawl. I have no idea why. CPU activity is very low on both cores, gobs of memory.
It's almost as if it's waiting for something but I have no idea what. I have disconnected all USB and FireWire devices but it helped only a little bit.
Any ideas?
First thing I'd look at is the HDD. Is it constantly being accessed? If so, it would indicate several possible things - memory shortage and lots of swapping, hard drive free space shortage cause it to hunt for space, heavy fragementation etc.
If thats not it, perhaps Xcode is running something in the background. Do you have any custom scripts you have added which could have done something?
have you rebooted?
It sounds like you have predictive compilation turned on in the Xcode preferences.
I know this is a relatively old post, but I had a different problem that was causing XCode to be sluggish. I am running 4.1. If you navigate to your project file, secondary click and select "Show Package Contents", then delete the *.xcworkspace file, XCode speeds up drastically. No more rainbow pinwheel of death.
It may very well be downloading documentation updates. They're fairly large. Open Xcode's (note, big X, little c :-)) preferences and go to the documentation tab. I'll bet there's a circular progress indicator beside one of the doc sets.
If you have lots and lots of code (or at least 10 000++ lines of code), the predictive compilation setting gets a lot to do. Turn this off as mentioned and you've at least eliminated that variable.
For me, this just happened when I started editing a new file. It was caused by a single function -- something in that function caused the compiler to freak out. After 20 minutes of compiling, Xcode gave me that message.
So if something like this starts right when you start editing a file, try commenting out the problem areas and trying again.
Ever since I started using Xcode, I've experienced extremely annoying problems with Code Sense. The problem is that when Code Sense kicks in for code completion, sometimes the source code text below the line I'm working on goes "crazy". If I continue typing, the problem gets worse, and after a while the source code is completely screwed up (funny colors, missing lines and characters, ...). Strange enough, the source code itself is unaffected, because when I select another source file and then go back to the one I was working on, everything looks fine again.
The problem can be seen in this screencast: http://www.screencast.com/t/OGY3NWE5
Interesting facts:
This problem has occurred on 3 different machines, so it's not related to a corrupt installation.
Sometimes it's fine for a while (up to one hour) after launching Xcode, but once it starts happening, it's getting worse and worse, until Xcode is restarted. Then it's fine again (for a while)
I've searched the web for similar experiences, and I can't find anything. I would think that it is a known problem, since it occurs on 3 different Macs here (both running 10.5 and 10.6).
Anyone having the same problems? Or a suggestion for fixing this?
Yeah, it can be a real pain. I didn't find a 'fix for it as such, but I do a quick switch from implementation to header (or vice versa) and then back again using Command-option-up. The screen redraws and everything is fine again
Well, I finally (kind of) fixed this problem by simply turning off Quick Help. Previously, I left this on all the time, and it resulted in a very unstable code sense (to the point where Xcode simply became unusable).
This is not a real solution, but it should at least help people experiencing the same issue.
I wrote about it here
My issue was with localization. if your XIB file is localized using xcode 4's, then it was failing for me. removing the localization worked, though not a proper solution.
I saw that Beta 1 of VS2010 was publicly availible.
My question to those of you who has tried it is: does it work good?
Will it cause my computer to blow up in tiny pieces? Will it crash randomly? Will it work with some minor glitches? Or is it just perfect from bottom up?
I'm only coding school- and hobby-stuff, so nothing that someones life depend upon, but i still want software that works. How close to a final product is it? Is it worth trying?
It's a bit slow, and there's no offline MSDN, but it's worth trying IMO. Having said that it's slow, I still use it on my NC10 netbook, so it's clearly not that bad :)
I've got it side-by-side VS2008, and that hasn't caused any problems.
I've seen a couple of glitches (once the keyboard handling went completely wonky) but it's certainly usable. The main question is what you want to get out of trying it - in my case I absolutely need to code against C# 4 to explore the new features. I do most of that from the command line in fact, where the speed of VS obviously isn't an issue, but it's nice to see the VS-specific features as well (like the debug threading views for Parallel Extensions).
It seems more or less usable on the .NET side. The C++ side is a bit more sketchy. On one hand, they've added support for some very nice new C++0x features, on the other, they've broken some absolute fundamentals.
Your plain old main function won't compile in 32-bit with unicode enabled. (Workarounds: Either compile as 64-bit, disable unicode, or rename the function to wmain).
This seems to me to be a strong hint that the C++ side of things is nowhere near release-worthy. I'd probably wait for beta2 before doing any serious work with that.
I would say it is great, but the performance hurts a bit.
Here is an idea for you: Install it into a VirtualPC. Then you can play and not care what it does. You don't like it, delete the VPC image and keep on trucking. That is how I play with Microsoft betas now. I never install them on any real machine - too risky.
Usable: Yes.
Recommended: Not if you'r a touchpad-addict or dislike crashing apps.
I've been trying it for 2 weeks now coding small C#-projects and these are my impressions
Reasons to use 2010:
Looks good
Multi monitor support
I can see myself using the code templating but right now i couldnt find any really useful stuff except for reducing the fontsize of comments.
Zoom in the editor
Select a variable and then press shift+up/down to go to next usage of this variable
Ctrl+, brings up instant search of classes and functions in the entire project. (i've become really addicted to this)
Floating watches for single objects
Reasons to not use 2010:
TOUCHPAD SCROLL DOESN'T WORK IN THE EDITOR!!! (this is reason enough to not upgrade if you are using it on a laptop)
I've had some random app-crashes in the middle of just writing code, once or twice per day maybe.
UI sometimes freezes randomly for about 30seconds and then returns to normal.
It started to use 100% CPU power from one of my cores once when it was minimized in basic editing-mode and i was doing other stuff in other programs, i only noticed it because the fan started to go wild.
Otherwhise it's pretty similar to 2008. I haven't noticed any difference in speed like other people say.
You need to ask yourself: what is the advantage for you in using VS2010 over VS2008? I would suggest that there is no advantage if all you are doing is "school- and hobby-stuff".
I'm still using VS2008 for business related stuff (and, indeed, VC6 for some stuff). I prefer to wait until all the early adopters have tested it (and Microsoft has released at least one service pack after the real product release) before I do their testing for them.
It seems to co-exist with other versions of VS without causing any problems.
Regarding the slowness - it seems to be the UI that is slow, rather than building. Once it's going it doesn't seem much slower on my fast quadcore. I've yet to try it on my laptop.
It's usable enough, the small glitches that I've encounter weren't that bad. However, certain VS extensions(like XNA) don't work in VS2010 at the moment.
It's fun to toy with. Not usable for me, cause re#er does not support it yet (had to install TestDriven .NET which works through keyboard shortcuts only to run my tests).
Gave me an insight how addicted I am. :/
Btw, on Win7, without virtual pc it seemed even faster than vs2008 for me.
VS2010 doesn't yet support mobile device projects, which might or might not matter to you.
VC++ wise - VS2010 has a built-in 64-bit compiler, VS2008 does not.
You can supposedly add 64-bit support to VS2008, but it takes some effort.
I've been using VS 2010 beta (with .NET 4.0 beta) on Windows 7 RC. I've been trying to rewrite parts of a large-scale business application in it to see what can be done with it.
The UI freezes frequently. I'm talking 1-10 minutes between freezes. The UI does not come back, so I'm forced to kill devenv.exe every time it happens. Microsoft probably puts my error reports in their spam folder by now.
For me, VS 2010 beta 1 classifies as unusable. However, it's fast, the new IDE functions are very handy, and it's pretty. I keep coming back to it despite my resolutions to wait for a stable build.
By 'challenging development environment' I don't mean you're on a small boat that's rocking up and down and someone is holding a gun to your head. I mean, are the tools at your disposal making the problem difficult?
Development is typically a cycle of code, run, observe the result, repeat. In some environments this is a very quick and painless process, but in others it's very difficult. We end up using little tricks to help us observe the result and run the code faster.
I was thinking of this because I just started using SSIS (an ETL tool included with SQL Server 2005/8). It's been quite challenging for me to make progress, mainly because there's no guidance on what all the dialogs mean and also because the errors are very cryptic and most of the time don't really tell you what the problem is.
I think the easiest environment I've had to work in was VB6 because there you can edit code while the application is running and it will continue running with your new code! You don't even have to run it again. This can save you a lot of time. Surprisingly, in Netbeans with Java code, you can do the same. It steps out of the method and re-runs the method with the new code.
In SQL Server 2000 when there is an error in a trigger you get no stack trace, which can make it really tricky to locate where the problem occurred since an insert can have a cascading effect and trigger many triggers. In Oracle you get a very nice little stack trace with line numbers so resolving the problem is very easy.
Some of the things that I see really help in locating problems:
Good error messages when things go wrong.
Providing a stack trace when a problem occurs.
Debug environment where you can pause, then output the value of variables and step to follow the execution path.
A graphical debug environment that shows the code as it's running.
A screen that can show the current values of variables so you can print to them.
Ability to turn on debug logging on a production system.
What is the worst you've seen and what can be done to get around these limitations?
EDIT
I really didn't intend for this to be flame bait. I'm really just looking for ideas to improve systems so that if I'm creating something I'll think about these things and not contribute to people's problems. I'm also looking for creative ways around these limitations that I can use if I find myself in this position.
I was working on making modifications to Magento for a client. There is very little information on how the Magento system is organized. There are hundreds of folders and files, and there are at least a thousand view files. There was little support available from Magento forums, and I suspect the main reason for this lack of information is because the creators of Magento want you to pay them to become a certified Magento developer. Also, at that time last year there was no StackOverflow :)
My first task was to figure out how the database schema worked and which table stored some attributes I was looking for. There are over 300 tables in Magento, and I couldn't find out how the SQL queries were being done. So I had just one option...
I exported the entire database (300+ tables, and at least 20,000 lines of SQL code) into a .sql file using PhpMyAdmin, and I 'committed' this file into the subversion repositry. Then, I made some changes to the database using the Magento administration panel, and redownloaded the .sql file. Then, I ran a DIFF using TortioseSvn, and scrolled through the 20k+ lines file to find which lines had changed, LOL. As crazy as it sounds, it did work, and I was able to figure out which tables I needed to access.
My 2nd problem was, because of the crazy directory structure, I had to ftp to about 3 folders at the same time for trivial changes. So I had to keep 3 windows of my ftp program open, switch between them and ftp each time.
The 3rd problem was figuring out how the url mapping worked and where some of the code I wanted was being stored. Here, by sheer luck, I managed to find the Model class I was looking for.
Mostly by sheer luck and other similar crazy adventures I managed to work my way through and complete the project. Since then, StackOverflow was started and by a helpful answer to this bounty question I was able to finally get enough information about Magento that I can do future projects in a less crazy manner (hopefully).
Try keypunching your card deck in Fortran, complete with IBM JCL (Job Control Language), handing it in at the data center window, coming back the next morning and getting an inch-thick stack of printer paper with the hex dump of your crash, and a list of the charges to your account.
Grows hair on your fingernails.
I guess that was an improvement on the prior method of sitting at the console, toggling switches and reading the lights.
Occam on a 400x transputer network. As there was only one transputer that could output to console debugging was a nightmare. Had to build a test harness on a Sun network.
I took a class once, that was loosely based on SICP, except it was taught in Dylan rather than Scheme. Actually, it was in the old Dylan syntax, the prefix one that was based on Scheme. But because there were no interpreters for that old version of Dylan, the professor wrote one. In Java. As an applet. Which meant that it had no access to the filesystem; you had to write all of your code in a separate text editor, and then paste it into the Dylan interpreter. Oh, and it had no debugging facilities, of course. And being a Dylan interpreter written in Java, and this was back in 2000, it was ungodly slow.
Print statement debugging, lots of copying and pasting, and an awful lot of cursing at the interpreter were involved.
Back in the 90's, I was developing applications in Clipper, a compilable dBase-like language. I don't remember if it came with a debugger, we often used a 3rd-party debugger called 'Mr Debug' (really!). Although Clipper was fast, some of our more intensive routines were written in C. If you prayed to the correct gods and uttered the necessary incantations, you could use Microsoft's CodeView debugger to debug the C code. But usually not for more than a few minutes, as the program usually didn't like to spend much time running with CodeView (usually memory problems).
I had a series of makefile switches that I used to stub out the sections of code that I didn't need to debug at the time. My debugging environment was very sparse so there was as much free memory as possible for the program. I also think I drank a lot more back then...
Some years ago I reverse engineered game copy protections. Because the protections was written in C or C++ they were fairly easy to disassemble and understand what was going on. But in some cases it got hairy when the copy protection took a detour into the kernel to obfuscate what was happening. A few of them also started to use of custom made virtual machines to make the problem less understandable. I spent hours writing hooks and debuggers to be able to trace into them. The environment really offered a competetive and innovative mind. I had everything at my disposal save time. Misstakes caused reboots and very little feedback what went wrong. I realized thinking before acting is often a better solution.
Today I dispise debuggers. If the problem is in code visible to me I find it easiest to use verbose logging. (Sometimes the error is not understanding the interface/environment then debuggers are good.) I have also realized time is of an essance. You need to have a good working environment with possibility to test your code instantly. If you compiler takes 15 sec, your environment takes 20 sec to update or your caches takes 5 minutes to clear find another way to test your code. Progress keeps me motivated and without a good working environment I get bored, angry and frustrated.
The last job I had I was a Sitecore Developer. Bugfixing can be very painful if the bug only occurs on the client's system, and they do not have Visual Studio installed on the system, with the remote debugging off, and the problem only happens on the production server (not the staging server).
The worst in recent memory was developing SSRS reports using Dundas controls. We were doing quite a bit with the grids which required coding. The pain was the bugginess of the controls, and the lack of debugging support.
I never got around the limitations, but just worked through them.
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Did you ever had a bug in your code, you could not resolve? I hope I'm not the only one out there, who made this experience ...
There exist some classes of bugs, that are very hard to track down:
timing-related bugs (that occur during inter-process-communication for example)
memory-related bugs (most of you know appropriate examples, I guess !!!)
event-related bugs (hard to debug, because every break point you run into makes your IDE the target for mouse release/focus events ...)
OS-dependent bugs
hardware dependent bugs (occurs on
release machine, but not on
developer machine)
...
To be honest, from time to time I fail to fix such a bug on my own ... After debugging for hours (or sometimes even days) I feel very demoralized.
What do you do in this situation (apart from asking others for help which is not always possible)?
Do you
use pencil and paper instead of a debugger
face for another thing and return to
this bug later
...
Please let me know!
Some things that help:
1) Take a break, approach the bug from a different angle.
2) Get more aggressive with tracing and logging.
3) Have another pair of eyes look at it.
4) A usual last resort is to figure out a way to make the bug irrelevant by changing the fundamental conditions in which it occurs
5) Smash and break things. (Stress relief only!)
I once worked for a company that sold a client-server application that was basically a file transfer and synchronization tool. Both the client and the server were custom applications we had designed.
We had a persistent bug that was very hard to duplicate in the lab. Our server could only handle a certain number of incoming client connections per box, so many of our customers would "cluster" multiple servers together to handle large user populations. The back end data for the cluster was on a file server they all shared. In this cluster configuration there was a bug that would happen under load where we would get a low-level file system error code on a file sharing call involving one of the back end files. Nobody could get this to repeat reliably in the lab, and even when they could they couldn't narrow down what was happening.
(I forget the exact error, it was probably 59 ERROR_UNEXP_NET_ERR or maybe 65 ERROR_NETWORK_ACCESS_DENIED. As I recall it was not even one of the documented error codes you were supposed to be able to get from the API we were calling, which was usually a lock or unlock call on a file section).
Since it involved the communication between the server and the back-end file store, and I was the "network transport" guy, I was tasked with looking at it. Many others had looked at it with no luck.
The one solid thing I had was I knew where in the code the error was being detected, but not what to do about it. So I needed to find the root cause. So I set up an appropriate hardware environment to duplicate it, and I put a custom build of the server software that instrumented the section of code in question.
The instrumentation was as follows: I added a test for the troublesome error code, and had it call a piece of code to send a UDP packet to a predetermined network address when the error occurred. The UDP packet contained a unique string in it to key on.
I then set a packet sniffing tool on the network. (At the time I was using Microsoft Network Monitor). I positioned it where it would be able to "see" this UDP packet when it was sent as well as all the communication between the cluster servers and the file server.
Most good sniffers have a mode where you can have it capture until it sees a particular piece of traffic, then stop. I turned on that mode and set it to look for that UDP packet my code would send. The goal was to end up with a packet capture of all the file server traffic right before the bug occurred. The very last network packets to and from the system where the UDP packet originated would presumably be a big clue as to what was happening.
I set the "stress test" configuration going and went home for the weekend.
When I got back on Monday, lo and behold I had my data. The sniffer had stopped just as expected after many hours of running and contained a capture. After studying the capture, what I found was that the Server Message Block or SMB (aka CIFS aka SAMBA) connection between our server and the file server was actually timing out at the TCP level due to extreme loading on the server. Because all of Microsoft's stuff is heavily layered, it would percolate back up through the file sharing stack as an "unexpected" error instead of returning a more intelligible error code that said "hey, you lost your connection at the TCP level".
I did a little more research on the TCP settings for Windows, and lo and behold the defaults for the version of Windows we were using (probably NT 4 in that era) were none too generous. It was only allowing for a very small number of failures on the TCP connection and boom, you were dead. Once you lost your SMB connection to the file server, all your file locks were toast and there was no way to recover.
So I ended up writing an appendix to the user manual that explained how to alter the TCP settings in Windows to make your cluster server a bit more tolerant of high load situations. And that was it. The fix to the bug was zero change in code, merely some additional documentation on how to properly configure the OS for use by this product.
What have we learned?
Be prepared to run altered versions of your code to investigate the problem
Consider using non-traditional tools to solve the problem (sniffers)
Not all bug fixes require code changes
Sometimes you can diagnose a bug while at home having a beer
I do a number of different things:
throw out all my assumptions and start from scratch. Remember, a bug exists because something which appears correct is actually wrong. Even those lines or functions or classes that you are absolutely certain are correct may be incorrect. Until you can convince yourself of the correctness you can't assume anything is right.
keep putting in print statements and assert statements to eliminate things and allow me to reform new assumptions.
step through code in the debugger if the problem is a control flow problem. Don't step over functions. Step in them and go through all the detail of their execution to confirm they are working right. Confirm the arguments and return values.
If a line or function or class is suspect but I can't prove it in situ, then write a small test case that does what you think the problem construct does. This may locate the problem or give some insights as to where to look next.
stop for the day. It's amazing what kind of offline processing your brain will do overnight. Often the answer or a key insight will appear the next day while I'm doing something mindless like showering or driving.
Create an automated way to cause the bug. The worst bug to fix is one that takes hours to reproduce.
Quote taken from "The Cryptonomicon":
"Intuition, like a flash of lightning, lasts only for a second. It generally comes when one is tormented by a difficult decipherment and when one reviews in his mind the fruitless experiments already tried. Suddenly the light breaks through and one finds after a few minutes what previous days of labor were unable to reveal."
I usually ask someone else to take a look at the code. While I'm explaining what the code is supposed to do, I sometimes see the bug just as I talk.
When a bug is a tough one, I sit and work until I figure it out and solve the problem. Interestingly enough, there are times when catching a mysterious bug is more enjoyable than everything running smoothly. And the relief and feeling when a bug is resolved, well, not many other things can beat that (except the obvious ones).
If all else fails, don't tackle it directly. Rewrite the problem area code in a more refactored way.
I have definitely had bugs which I worked on for 4-5 days continuously before finding a solution. Other bugs have sat in the bug tracker for months, as I put in a few hours spread out over a long period of time. I think this sort of bug is inevitable in any complex software project.
Some stuff that works well for me:
binary search through the program flow with logging
use Trace statements along with DbgView to search for bugs which show up in release mode
find an alternate way to reproduce the bug without changing the code
(works against logic, but...) change the code so that the bug is more easily reproducible (the failure condition is more readily achieved)
sleep on it and try again tomorrow with a fresh pair of eyes :)
The worst sort of bug in my opinion is a concurrency bug which disappears when logging is inserted.
Lots of great answers here. One thing that's worked for me in the past is to ask "what can I do to make it totally obvious when this problem has occured?".
For example, if the problem is a corrupted value in a data structure, try building a consistency-check routine that you can run periodically. Also consider implementing all access to the shared data through a set of functions that log each change.
Or, if the problem is a "random" memory overwrite, use a replacement malloc()/free() implementation that traps writing to "free" memory (like electric fence or dmalloc).
Someone else mentioned automating the process of triggering the bug. This is greeat if you can do it. Even having a routine that randomly exercises the program might help in these cases.
Seriously? I do things in this order.
Go to bed
Ask a colleague
Rewrite so the area isn't affected.
Ask SO
Raise a support ticket with your 3rd party library vendor.
"What do you do in this situation (apart from asking others for help which is not always possible)?"
When is it not possible to ask for help?
There are always others you can turn to for assistance - your coworkers, your boss, friends here at Stack Overflow, etc.
Understanding when to seek help shouldn't be demoralizing!
There are a lot of good tips here.
One that I absolutely do not agree with is the concept of changing the code hoping that it will go away. First off, you a probably going to introduce new bugs. Seconds, you can easily change things enough to hide the bug only to have it resurface again with the next patch.
Memory corruption bugs are especially likely to vanish as magically as they turn up. However, the memory corruption bug isn't fix, it is only that non-fatal areas of memory are getting trashed.
1) Try a different debugger. For example, I use WinDbg more and more often. When you load a program in a debugger, memory layout for your application will change slightly. Maybe a different debugger cause the error to manifest slightly differently.
2) If you resort to changing code without knowing exactly what the problem is, then if the bug goes away, YOU MUST go back and understand why the change fixed the bug. Otherwise, you are probably just hiding the bug.
3) Talk to others about the bug, maybe they have seen different versions of the same problem (i.e. other ways to recreate it)
4) Logging.
I've had bugs that took weeks or months before a solution was found, but eventually all bugs do get fixed. Aside from the classical non-debugger bug-tracking techniques like disabling parts of the system until you get a minimal test case, I've used these techniques:
Looking for better debugging tools. A new perspective goes a long way. Xdebug is something I started using in PHP only because of a performance bug that I wasn't making headway on.
Studying the technology that the bug is located in. This has helped to debug an outlook add-in. It had random errors that made no sense and that google searches turned up zilch about. By researching outlook add-in best practices, COM and MAPI programming, we got a clearer picture of what could go wrong, and thought of new things to try to fix the bugs, which eventually did fix them.
Trying to exacerbate the problem. If there's an issue that only happens occasionally, I'll try to find ways to make it happen constantly. This has helped to track down errors in web apps under IE and also to narrow down a crashing bug in the flash plugin.
When all else failed, I've rewritten the subsystem that caused problems from scratch. This may take a few days, or even weeks, but if you're stuck on a bug, and can't resolve it, and customers won't take no for an answer, what else can you do? This doesn't always fix things, but if it doesn't, you usually get a clearer picture of what's going wrong.
I've noticed a few commonalities in these bugs that I get stuck on for weeks:
Asking 3rd parties for help rarely helps, and it's generally not a good idea to wait for someone else to come save the day.
Almost always the fault is inside some 3rd party closed source technology, especially when using obscure parts. IE had nasty bugs when trying to use client certificates. Flash didn't deal well with randomly generated drawing instructions (some of which were nonsensical). Outlook doesn't like it when you try to change form layout dynamically from code. These days I've learned to respect the "comfort zones" of proprietary tech.
I give it more time. I once had a bug (in a personal project) that I just could not figure out. I tried every debugging method I could think of, including Google, with no success. Six months later, I came back and found the bug within an hour or so. It wasn't something simple (something apparently undocumented was going on deep inside Swing), but I just looked at it in a way I hadn't before.
I've had this problem before, I believe everyone has, I have flat out given up before, it was simply impossible to find, yet it kept crashing, when theres some kind of bug in the code, what I do is just sit down and concentrate on every bit of the code little by little until I find it, it's hard and it takes patience but it's all you can do in such a situation.
Hope this helps.
I honestly cannot recall a bug that I couldn't fix. It may cause a lot of refactoring, or may take a while, but I've never had one that I can't get rid of. If it takes me more than an hour to track it down then it's almost always something really stupid and small like looking right past that : that should've been a ;, etc.
In python, if I'm using an editor that isn't mine, or maybe it's someone else's code, I use retab! in vim, or paste into something like pastie to check indentation (if I don't have vim available).
If it's not a crasher/deal breaker, then I move on and come back with a fresh pair of eyes.
Oh, and you can never, ever have too much logging.
I add as much debug as possible (write to log file, message boxes, etc.), and test.
I don't think this is the worst bug you can find. The worst ones are those you can't reproduce deterministically or in the testing environment.
I get a bit demoralized too when unable to solve a bug. Usually when I hit a wall with a bug, I would just take note on my findings and stop working on it. I would jump on another bug that is easier to solve and then came back to the bug. By doing this, I would have a fresh mind and attitude in tackling the bug. Sometimes you might have tendency to overcomplicate things when spending too much times on a bug. Having a break, helps in breaking the wall.
RWendi
First off, is it reproducible? That's a HUGE plus if it is. I want things bugs to always/never happen... its the intermittent ones that are the troublesome ones.
And it is going to depend on the problem, but at my shop we'll generally tag-team such a problem figuring that 2 heads (or 3 or 4) is better than 1.
Occasionally the bug won't even be in MY code, but it generally is. There have been issues where a 3rd party library was the culprit or a particular implementation on a particular platform was the cause - those stink.
I'll use anything and everything to at least track it down: debuggers, trace output, whatever.
Typically, if I can isolate it to a class or module I'll write a test harness to duplicate the real world and try to duplicate it there. I generally write my test code first, but sometimes legacy code (or other developer's code) exists that doesn't have tests already.
I generally will talk the design and problem through, out loud with the team and whiteboard anything that isn't clear. Often the solution will bubble to the surface once we talk about it as a group.
That's what I do.
I usually, try hard solving it. But, if that is not possible for reasonable windows of time, I leave it for some time to braincells to solve it while i sleep ;) Sometime it works...
I've considered asking for help on this website called StackOverflow that I've been frequenting lately...
This is what I did today...
I debug HW/SW interaction and its often the case logging (instrumentation) changes or hides the bug. Hence tests are performed "at-speed". I call these bugs "roaches" as they run away from any light I can shine on them.
So I have to:
Find the transaction that causes the bug. List the HW interaction via logging (this test passes, but it illustrates the flow).
Instrument before and after the bug to print state changes.
The bug I'm solving now of course is worst case as the HW locks up. The HW includes the CPU so its like being in a well lit room then the power fails and its pitch black.
I have a special backdoor view into memory, but of course this is locked up also. I tried power cycling in the hopes that the memory would stay non-volatile long enough to reenable the backdoor. No such luck. This is possible though.
I very very carefully wrote all the steps I went through to characterize this bug (what works, what fails etc). Sent this to developers with similar HW to verify it just wasn't me or my HW.
I took a few hours break to let this info settle and see if any lightbulbs lit elsewhere.
No replies, this bug is mine to solve...
This HW SW interaction is a loop tha does some setup then enters a polling loop that reads when the transaction is finished. Many transactions should occur. Which transaction fails? Is it the first one (indicating I can debug the transaction and not some noise in the HW). Is it the always the Nth transaction? What makes the Nth different than the first or the (N-1)th. The SW is single threaded and built to be predictable. No preemption, no interrupts enabled.
This SW has worked before, whats new? All the HW is new. In this case all the silicon is new as its an ASIC. Even the embedded CPU is new and customized so the ISA is new.
So I suspect everything and I'm blind. I'll have to sneak up on this roach.
I enabled just the log that reports how many times the SW polls the HW for completion. In this way the first transaction runs at speed, I get an idea how often I touch the HW in a tight polling loop. The test passes. I know its the Nth transaction and I recorded the peak number of polls for all transactions (perhaps meaningless data).
After modifing anythin, I have to put it back the way it was to verify the bug still exists. After all the earth has rotated and the solar winds are not as strong ;)
Looked at all the checkins, saw a contractor changed some important setup parameters with no explanation. These (outsourced) people are still under evaluation. This will not help.
Found there was no spinwait in the polling loop. Bad for the loop timeout as without it the timeout depends on CPU speed. Added spinwait, still no happiness.
Limited the number of transactions to see where it fails, somewhere before 1000.
Setup the HW to run slower, still hangs.
Hate to leave anyone reading this hanging too, but this diatribe will have to wait till tomorrow.
There is no bug that can't be fixed, since there is no bug that can't be fixed with a total rewrite.
An unfixable bug is just a bug you aren't willing to replace.
For memory related bugs i have found that the Memory Profiling options of Ants Profiler have helped me quite a bit on finding bugs.
use more creative methods of tracking the bug down.
using remote debugging on the machine where its reproducable.
using profiling tools.
introduce more logging to the app.
Going away for a while and then coming back to a problem is one common approach I do and have heard.
How easily reproduced the bug is can be a factor as well since if the error only occurs in one in a zillion runs of a program that could be considered a negligible gain for fixing it by breaking something else.
There is also the question of nailing down where the bug is, is it in some configuration so that it occurs on a server but not my local XP Pro machine which runs IIS 5.0. Some other bugs may involve having to change the resolution of my machine that can be annoying to try to reproduce a bug that others have reported.
You left out the "occurs under another O/S" category of bugs so that a web page that is fine in IE and Firefox on PC may look like crap on Safari on a Mac. Do I get my hands dirty in trying to fix a CSS issue using my machine as a server and the Mac that is over a row or two in the cubicles of the floor in order to see this issue or is it so low a priority it gets swept under the rug? Alternatively, if a bug was on Linux and there aren't any Linux machines near me, what should I do?
I'm sorry to have left with some questions but these seem to be difficult questions for me at times.
In addition to the debugger, I've also used logging and old fashioned paper and pencil. On occasion I've found really hard bugs, like code that runs fine in debug mode, but breaks in release mode. I've even occasionally rewritten perfectly good code that for whatever reason, doesn't work reliably, figuring that it's better to be reliable than elegant.
I sometimes try to redefine what others term a bug as really being a feature, but that seldom works!
I have a bug that shows up every few months on a customer site. It usually happens at 3am and it's not discovered until early the next morning when the customer arrives at their site. And usually when they discover it, they want everything to get working immediately, so our support people generally just reboot the computer. It's been driving me nuts for years. It never happens on my test machine or in the QA lab, only at certain customer sites. Over time, I've
refactored some of the code that I thought was causing it
added more debugging printouts around where it appears to be crashing
redirected stdout so that next time I see it I can "kill -3" the process
given support some new tools to dump out the current state of database locks and the like.
added diagnostics to make it more obvious when it does happen
It hasn't happened in a few months, and I've got my fingers crossed that I might have fixed it this time, but I'm not counting on it.
If it's not critical, don't fix it, you'll just spend too much time!
Keep the bug open. comment/work on it when you can. It might get fix by accident (or by someone else) later on!
Sometimes it takes a little lateral thinking, but every bug is fixable. Sometimes you need to leave it and sleep over it, sometimes it's good to ask someone else to have a quick look (they may see something you haven't), but mostly it's about trying different things, calling up on previous experience. It can be frustrating, but the buzz you get when you do fix it, is like no other!