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Re (tilly) 2: Are debuggers good?

by tilly (Archbishop)
on Dec 28, 2000 at 17:40 UTC ( #48621=note: print w/replies, xml ) Need Help??

in reply to (tye)Re: Are debuggers good?
in thread How to debug unknown dynamic code?

I just can't believe all of the people who use debuggers who think that people like Randal and I are just taking a position out of ignorance of how to use a debugger!

Follow through the thread of discussion in the conversation that I pointed to. The exact issue of Kernel Threads under discussion which I pointed to is here, check out sections 1 and 4. In particular the following posts stand out as being particularly relevant. First the one where Linus says, "I am a bastard, and that's OK", and IBM's experience.

Both of those articles are written by competent programmers with years of experience developing in a very complex environment who both know debuggers. Both claim that while debuggers look easy, neither think that they really help. If you read those threads you will find many competent people who absolutely disagree with that position. There are people on either side.

Note that I didn't say that debuggers are useless for debugging. I said I am constantly amazed at how many good programmers don't like them for that purpose but have plenty of other uses. It should be obvious that good programmers who have found other uses for a debugger actually understand what they are and how to use them. Ignorance is not the reason for not choosing to use them.

No, the reason is more subtle. The limit to our ability to develop interesting things lies in our ability to comprehend. Debuggers focus intention at the wrong point. They let us blindly trace through code to find the symptoms of problems. That doesn't help us one bit to notice more subtle symptoms of structural problems in the code. It doesn't help one bit in giving us encouragement to be more careful. It doesn't encourage reflection on the process. It doesn't give us reason to think about the poor schmuck that has to handle our code afterwards.

In short it encourages missing the forest for the trees. But in the end projects are felled by overgrown thickets, not by single trees.

Now I know you will likely disagree. This is an opinion which many people are divided on. But my opinion just happens to be shared by a lot of very competent people. It isn't based on ignorance. Instead it is based on experience and thought about the process. I have repeated this point to plenty of friends. Some make you go, "hmmm". Like the guy who said, "That is true. I have written debuggers. I used to use them all of the time. But then I thought about my own thinking process, and tried not using it for a bit. After that I never looked back."

However one thing we will both agree on. If you don't think about your own development process on an ongoing basics, then there is no question that a debugger would be helpful. They are effective tools, no question about that.

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(tye)Re2: Are debuggers good?
by tye (Sage) on Dec 28, 2000 at 23:13 UTC

    I don't know you, tilly, nor merlyn. Most of the programmers I know that won't use a debugger for debugging don't know how.

    My point was that if you want to debug by adding trace output, then you can do that very well with a debugger (and I think you can "add trace" much more efficiently with a debugger -- though adding the trace during development and being able to enable it in production is an even better idea that still doesn't eliminate the usefulness of a good debugger). So I don't understand the argument that you don't use a debugger for debugging because instead you do it by adding trace.

    And I do disagree with the undertext that using debuggers means that a programmer isn't being careful up front or that it leads to programmers who aren't careful up front. I find more bugs in other people's code than in mine, even when debugging my own code. I spend a great deal of time figuring out how to work around other people's bugs because I don't have the option of fixing them even though I've found them.

    I do wish that other programmers would be more careful (as I talked about previously in (tye)Re: Why, not How). I don't think (as Linus seems to) that taking away debuggers will have any positive effect at all. That would just mean that when bugs crop up (which never happens to tilly nor merlyn because they are careful, despite having seen several of their bugs myself), more time will be spent tracking down that bug so there will be less time for improving other aspects of the software.

    I really doubt that it will be possible to remove many bad programmers from the profession (no matter how hard we manage to make programming). A bad programmer with a debugger still wastes plenty of time and has lots of motivation to be more careful. In fact, I've seen use of a debugger help a bad programmer learn how to be a better programmer.

    Never attribute to laziness what can be explained by ignorance. I think that most bad behavior that is blamed on laziness (or not being careful) has more to do with ignorance.

    [Debuggers] let us blindly trace through code to find the symptoms of problems.

    See, you think you know how to use a debugger but that statement tells me that you really don't. I never debug with a debugger by blindly tracing through code. My word, that would be a huge time sink.

            - tye (but my friends call me "Tye")
      Please step back before ranting.

      I have bugs. Of course I have bugs. When I post stuff off the cuff here I have a lot of bugs. Particularly when I post stuff that I didn't run, let alone test like I do before checking stuff into CVS.

      I don't know anyone who doesn't have bugs.

      Now please read what you responded to. Again. Without jumping down my throat first off.

      When I say that debuggers allow us to blindly trace through code to find the symptoms of problems, I am not saying that that is the only way to use them. I am creating a caricature of the tendancy I don't like. When you use a debugger to find a problem in your code, you do indeed find the answer to that specific problem faster. But you lose an opportunity to review your logic and clean your code up, which can often solve more bugs and helps in comprehension. With the convenience and immediacy of a debugger, the details of what is happening are too handy and the thinking about why someone might not want it to be that way are too distant for my taste.

      In short, I don't mind having to work harder for most bugs if it means that I get to program in a way where I wind up with fewer bugs in the end. Particularly since I have a lot of error checks which mean that if something does go wrong, I usualy have all of the information that I want immediately available. And if I don't, well that usually means that something more serious was wrong.

      Besides which the ease of using a debugger can mask important warning signs. Warning signs that I would like to see.

      Now as for Linus, while I see what he says, I likewise disagree with his position but for rather different reasons. Linus has been (IMO rightly) accused of suffering from The Curse of the Gifted. I think that applies here, he is underestimating the value of a tool for people who are not in his situation. In particular read again IBM's experience and look at all of the things that debuggers are listed as good for there. Yes, I think that a kernel debugger would be good. It would help people learn how the kernel works.

      Note that all of my statements about not wanting to fix problems interactively don't mean that I don't think it isn't a great idea to learn from running stuff interactively. Just because Linus doesn't need to learn how the Linux kernel works doesn't mean that others wouldn't benefit from that! And it can be useful to step from time to time through fresh code...

        Yeah, I got the impression you were suffering from the "Curse of the Gifted" as well.

        At least it was labeled a rant. :-}

                - tye (but my friends call me "Tye")
        When you use a debugger to find a problem in your code, you do indeed find the answer to that specific problem faster. But you lose an opportunity to review your logic and clean your code up, which can often solve more bugs and helps in comprehension.

        I think I agree with you, but when I use debuggers, it's usually not on my code. In fact, I rarely use the perl debugger, because when I debug perl, its usually my own code :) I've on rare occasions used the perl debugger to help track down problems in library modules, but usually looking at the source is good enough because I find perl source easy to find, and (mostly) easy to follow.

        I've mostly used debuggers with monolithic 4gl code which would include libraries on top of libraries, and the only way to find a problem without inserting a zillion print statements was to run the debugger (and I don't want to fully comprehend all the code, at least not today, I just want to fix the problem). And I would inherit problems from other programmers who would work for days on a problem but couldn't use the debugger, and I'd solve it in a few minutes or hours. So IMO it just depends on the environment. I use the perl debugger so rarely that every time I have a notion to use it, I find I have to relearn it :-)

        Update: Oh, and one more reason I use the debugger less in perl is that you don't have to go through that 'compile it again' phase of the debugging process that you have to endure in other languages.

        Very late update: Recently, I found myself tracking down a problem with totally unfamiliar CPAN http/socket library code. I inserted a couple of $DB::single; statements rather than numerous print's (these were dynamically loaded modules, so this was the easiest way to set breakpoints) and learned something about HTTP...specifically about chunking in the responses.

Re: Re (tilly) 2: Are debuggers good?
by merlyn (Sage) on Dec 28, 2000 at 20:43 UTC
    I particularly like Linus' statement in that post:
    Quite frankly, I'd rather weed out the people who don't start being careful early rather than late. That sounds callous, and by God, it _is_ callous. But it's not the kind of "if you can't stand the heat, get out the the kitchen" kind of remark that some people take it for. No, it's something much more deeper: I'd rather not work with people who aren't careful. It's darwinism in software development.

    It's a cold, callous argument that says that there are two kinds of people, and I'd rather not work with the second kind. Live with it.

    I fully support that. There are far too many people who (attempt to) perform programming as a income activity who aren't really programmers. If you can't program careful enough to not need a debugger, then either slow down your rate of coding, or pick a different profession. Please.

    Thanks for the reference, tilly. That's the point I was trying to make earlier. I don't use a debugger, because I try very hard not to need one. {grin}

    -- Randal L. Schwartz, Perl hacker

      There are far too many people who (attempt to) perform programming as a income activity who aren't really programmers. If you can't program careful enough to not need a debugger, then either slow down your rate of coding, or pick a different profession. Please.

      This is, of course, true. There aren't enough real programmers around to cover all the programming jobs. And as the demand for IT staff increases the problem will only get worse.

      I was contemplating starting to run Perl courses in the UK, but perhaps I should just run programming courses first...

      ... or perhaps "programming" isn't something that can be taught.


      "Perl makes the fun jobs fun
      and the boring jobs bearable" - me

        Had to throw my .02 out when I read:
        perhaps "programming" isn't something that can be taught.

        IMHO its the term programming that keeps people from learning it.

        Programming is merely a stereotyped word that detracts the average person from more actively interfacing with thier computer; Therefore, programming is not a skill to be learned, but rather must be a personal goal to be attained.


Re: Re (tilly) 2: Are debuggers good?
by footpad (Monsignor) on Dec 29, 2000 at 00:41 UTC

    I'm not sure I read that the same way you may have. I thought tye was sharing some of the tricks learned while working with the language. While it's possible to interpret some moral judgements (to borrow a phrase elsewhere in the thread) from the post, I don't see anything specifically suggesting that you or merlyn are taking positions from ignorance.

    Perhaps that's my own judgement peering through.

    Regardless, it may be worthwhile to borrow a another concept from the monastic disciplines that inspired this site. Specifically, each travels their own path toward mastery.

    I don't use debuggers personally for many of the reasons cited in both camps. However, I do use them when necessary. They can be effective tools, but they should not be the only tool in your problem solving arsenal.

    In the end, we make choices by bringing our experience, knowledge, and creativity to bear on the problem at hand. Even bad choices can help illuminate the path.

      We definitely did read it differently. I was explicitly saying that I don't use the debugger for debugging, and in response to that tye answered saying that he thought that people don't use it because of not wanting to take time to learn to use the debugger. He went on to tell me to use one the next time I need to debug. Despite the fact that I am saying that my not using one is intentional.

      I read that as his not paying attention to what I said (the fact that I am making an intentional choice) and assuming that if I am exposed to the joys of debuggers then I (being a presumably sane human being) will convert.

      That is what I reacted to, and I don't think that I reacted particularly unreasonably to it.

        Oh, sorry about some of that. I was more responding to the thread and the "you"s should have been "one"s as I was addressing all of the readers and not you specifically.

                - tye (but my friends call me "Tye")

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