from Hacker News

Stack Traces Are Underrated

by zoidb on 3/10/25, 7:01 AM with 56 comments

• by bob1029 on 3/10/25, 9:51 AM

  Stack traces are your #1 ally when supporting someone else's legacy production pile.

  Once you get comfortable with how they work and what information they contain, you can hit the ground running anywhere. Stack traces will teach you about the product architecture faster than anyone on the team can.

  As you embrace them, you take the little bit of extra time to make sure they go well. For example, re-throwing exceptions correctly, properly awaiting results, etc. Very minor details that make all the difference.

  A broader outcome of this enlightenment is preference for monolithic products. Stack traces fare poorly across web service and API boundaries. If you've only ever worked with microservice architectures, the notion of a stack trace may seem distracting.

• by the_mitsuhiko on 3/10/25, 8:32 AM

  > But Rust has a better workaround to create stack traces: the backtrace module, which allows capturing stack traces that you can then add to the errors you return. The main problem with this approach is that you still have to add the stack trace to each error and also trust library authors to do so.

  That's technically true, but the situation is not as dire. Many errors do not need stack traces. That so few carry a backtrace in Rust is mostly a result of the functionality still not being stable [1].

  The I think bigger issue is that people largely have given up on stack traces I think, in parts because of async programming. There are more and more programming patterns and libraries where back traces are completely useless. For instance in JavaScript I keep working with dependencies that just come minified or transpiled straight out of npm. In theory node has async stack traces now, but I have yet to see this work through `setTimeout` and friends. It's very common to lose parts of the stack.

  Because there are now so many situations where stack traces are unreliable, more and more programmers seemingly do lose trust in them and don't see the value they once provided.

  I also see it in parts at Sentry where a shocking number of customers are completely willing to work with just minified stack traces and not set up source maps to make them readable.

  [1]: https://github.com/rust-lang/rust/issues/99301

• by CMDBob on 3/10/25, 10:40 AM

  A stack trace (or even better, a minidump with the call stack!) is one of the most useful debugging things for me. Hell, the call stack in general is super useful to me!

  I can look at a stack trace, go "oh, function X is misbehaving after being called by function Y, from function Z", and work out what's gone wrong from the context clues, and other debugger info. As a game developer, with codebases that are big, semi-monolithic codebases, it's essential, especially when code crosses the gameplay/engine and engine/kernel barriers.

• by montebicyclelo on 3/10/25, 9:00 AM

  Great point. I've found it's very often possible to understand and fix problems "one shot" from stack traces alone — and we're talking production builds here... So I wouldn't turn them off, (an idea mentioned in the article), unless profiling shows that they are one of the last things preventing the code from reaching the target performance.

• by windward on 3/10/25, 9:43 AM

  >Are they just not used to having them so that they don't miss them?

  The languages that I work in that don't print useful traces are typically strongishly-typed system languages. So I miss them - sometimes having to step through offending lines of code in a debugger - but I also completely avoid a whole class of bugs that are responsible for most of my stack traces in Python.

  TFA's example isn't one of these, but is a function that would have a return code checked and logged if erroneous. This class of bug also can't be inlined and makes an easy breakpoint-ee.

• by TinkersW on 3/10/25, 8:51 AM

  They are useful sure, and I print a stacktrace on any type of error/exception, but often breaking into the debugger is even more useful and faster as you can see local variables, program state, and what other threads happen to be doing.

• by anonzzzies on 3/10/25, 9:10 AM

  I am a big fan of Lisp SBCL stack traces; even in complex projects I never saw before, I'm almost always able to read, interpret and fix the issue just from that.

• by zokier on 3/10/25, 10:44 AM

  Kinda related, but I feel it would be useful for log entries to include file/lineno and/or some unique identifier. Helps both pinpointing where some weird message comes from, and for searching for specific entries in the logs.

  Sure, you can grep the log message but it can be difficult if it has some templating/formatting going on, and it can be pretty easy to end up with non-unique messages.

• by GuB-42 on 3/10/25, 1:50 PM

  I don't know if it is part of the reason but stack traces can be considered a vulnerability in some situations.

  Also, for "normal" errors, you shouldn't need a stack trace. For example, "file not found" is, from the point of view of the developer an expected situation and should be handled with the same amount of care as it the file was present. You don't dump the internals to the user when you have successfully opened the file, so don't dump them when you haven't.

  For unexpected errors (i.e. bugs), the crash, abort, panic, or whatever it is called in your language. These will usually give you a stack trace, or a core dump from where you can extract the stack trace and more.

  What I would wish for however would be a standard feature in languages to display a stack trace on command. Many languages have it, but even when they do, they could be more prominent. This way, if you encounter an unexpected situation you want to debug without crashing and without a debugger attached, you can call it.

• by albertzeyer on 3/10/25, 10:30 AM

  Stack traces are very valuable. Sometimes it can even help to attach them to some object creation, when you later wonder why/how/where this object was created. E.g. in TensorFlow, every single Tensor had a traceback attached to it, so when there was any error later on, it would show you where it was created. This is maybe less needed now with eager mode, but you might have other similar situations.

  One problem with stack traces is maybe that they can be too verbose. E.g. if you print them for any warning you print to log (or stdout). Sometimes they will be extremely helpful for debugging some problem, but in many cases, you maybe don't need them (you know why you get the warning and/or you don't care about it).

  You could also add more information to the stack trace such as local variables. That can be even more helpful for debugging then, but again adds more verbosity.

  For example, we often use this to add information about relevant local variables: https://github.com/albertz/py_better_exchook

  One solution to the problem with verbosity is when you have foldable text output. Then the stack trace is folded away (not shown in all details) and you can unfold it to see the details. See the DomTerm demo here: https://github.com/albertz/py_better_exchook#domterm

  Some more on text folding:

  https://github.com/PerBothner/DomTerm/issues/54

  https://gitlab.com/gnachman/iterm2/-/issues/4950

  https://github.com/xtermjs/xterm.js/issues/1875

  https://gitlab.freedesktop.org/terminal-wg/specifications/-/...

  https://github.com/vercel/hyper/issues/1093

• by harperlee on 3/10/25, 6:17 PM

  My main problem with (jvm) stack traces is that they generally don't include information about the values that are passed to the function calls, so you get the structure of the code, but not the actual value that could help you reproduce the error. I know that once you deal with relatively complex objects that are not trivially serializable you get an address, which is not super useful, but in some codebases / problem areas you still could be getting a lot of information that gets lost due to that design decision.

• by Chilinot on 3/10/25, 8:34 AM

  I have been an avid proponent of the way errors are managed in Rust and Go for a long time. However, this article raises a very good point. Before i started developing in Rust and Go, i did Java and python for several years. And damn, do i miss those stacktraces every now and then when something bad happens that isn't properly handled by the code.

  Still, i do think returning the error as a return value is better than having a completely separate flow when dealing with exceptions. I like that it forces me to properly deal with an error and not just ignore it and think something like "meh, i'll get to this later". Because i will never "get to it later".

• by cm2187 on 3/10/25, 9:25 AM

  In C# the quasi mandatory async/await for everything has many downsides, particularly for debugging. It breaks all stack traces. It also makes it impossible to pause the code.

• by fedeb95 on 3/10/25, 10:24 AM

  hiding stack traces is a bad practice and should be avoided unless you're in the last layer of the application (i.e. presentation to the user).

• by creshal on 3/10/25, 11:27 AM

  Stack traces are underrated, unless you're developing EnterpriseJavaSingletonFactoryAbstractionFactoryFactories, in which case they're buffer overflows on your poor log analyzer

• by someothherguyy on 3/10/25, 12:08 PM

  Stupid clickbait headline for a famished article

• by berkes on 3/10/25, 8:41 AM

  Way before I consistently used step debuggers and would just "print-debug" println("why are you here?") or "raise-debug" raise new Error("huh?"), I tinkered with a step debugger, but found it too complex and hard. But I remember that it also allowed me to move backwards in the stack.

  It allowed me to go some frames back - lines up, up in the stack. I don't recall the name of this debugger, nor what language it was. But I've never since seen this, yet very often wished I had it (for rust, javascript, python, mostly).

  Did I misremember? Can such a thing exist? Does it exist?

• by cyberax on 3/10/25, 8:30 AM

  Don't worry. Just wait until you start doing async stuff, especially with React.

  You'll be dreaming of good old times of linear stacktraces.

• by rollulus on 3/10/25, 9:32 AM

  Depends on the audience. As a user I'd rather see "can't load data: failed to parse header: wrong number of elements" than a stack trace with WrongNumbersOfElementsException at the tail.

• by logicallee on 3/10/25, 8:49 AM

  While you're debugging using AI (specifically, ChatGPT o1), you can benefit from copying stack traces. It debugs better than if you just describe what's wrong.

  Another tip: I have found that it is helpful to ask AI to "deeply analyze" (use those words) and think about the problem without providing a solution (say "don't reply with any code"). If you don't do that, it will take its first guess and then eagerly start outputing code that is still wrong and doesn't really identify or fix the issue. When you ask it to deeply analyze what's wrong and not reply with any code, it frequently finds the true underling problem, and then you can ask for how to solve it in the next step.