5 ms·

> "What's the weirdest bug you debugged? What made it weird?" If you can remember, 5-10 years after you solved it.

hiq 4y ago
It doesn't have to be true though, it just has to be a nice story. And this is the kind of interview questions you can prepare.
- epicureanideal 4y ago
  > It doesn't have to be true though ... This is exactly why it's a bad question.
Swizec 4y ago
Can’t have been that good a bug, if you can’t. Been close to 15 years since some of the horror stories I can tell. Hell, over 20 years for some of my favorite lessons. edit: Point is the good shit stays. You’ll remember the best stories, fear not.
- hgsgm 4y ago
  When you get older, other memories crowd out specific bugs. Memory is associative. The father you are from the bug, the harder it is to remember. More importantly, you don't need to remember your own bugs, you can get a story from the Internet or ChatGPT.
BoorishBears 4y ago
I would 100% accept that as an answer since it tells me the candidate is not good with subtext, and that's really needed to solve a lot of interesting problems. After all, if I ask "what's your favorite food you've ever eaten", there's an unspoken implication that it's a food you remember eating. I am not in fact asking you to recall every single food you've ever eaten and choose one... - From my comment below since every reply seems to be bent on ignoring the subtext even in a theoretical discussion about picking up subtext...: Again, the subtext is "interesting example we're going to discuss". If there's one you can't discuss for any reason (doesn't even have to be you forgot: could be an NDA) then it's already excused from the discussion. An even half-decent interview is not adversarial: just like day to day work, it requires interpreting some level of useful subtext and some level of open communication - I mean, you forgot the details so it's not like it's not like you're going to start monologuing if you just touch on it: "You know, there's a real doozy from X years ago where Y but the details escape me, more recently Z happened" If there are none that you remember that are interesting: "There aren't many interesting bugs, but there was this really interesting product requirement, could we go over that?"
- testTED 4y ago
  But you are asking for the most interesting example, which you may remember from context, but not in any interesting or even technical detail.
  - BoorishBears 4y ago
    Again, the subtext is "interesting example we're going to discuss". If there's one you can't discuss for any reason (doesn't even have to be you forgot: could be an NDA) then it's already excused from the discussion. An even half-decent interview is not adversarial: just like day to day work, it requires interpreting some level of useful subtext and some level of open communication - I mean, you forgot the details so it's not like it's not like you're going to start monologuing if you just touch on it: "You know, there's a real doozy from X years ago where Y but the details escape me, more recently Z happened" If there are none that you remember that are interesting: "There aren't many interesting bugs, but there was this really interesting product requirement, could we go over that?"
- neilv 4y ago
  > I would 100% accept that as an answer since it tells me the candidate is not good with subtext, [...] if I ask "what's your favorite food you've ever eaten", there's an unspoken implication that it's a food you remember eating. Will this filter cut many of the best engineers? Our field is full of people who pull 'engineering' out of our behinds, to various degrees. I'd assert that the engineer who doesn't assume an unspoken implication, but instead qualifies their answer, or tells you when they cannot answer, or asks for clarification... is more likely to be the one who can make a system that works, and tell you when a system will not work.
  - BoorishBears 4y ago
    > Will this filter cut many of the best engineers? It won't cut out a single good engineer, let alone the best. > I'd assert that the engineer who doesn't assume an unspoken implication, but instead qualifies their answer, or tells you when they cannot answer, or asks for clarification... is more likely to be the one who can make a system that works, and tell you when a system will not work. You grouped the one option that a bad engineer would take, with several that a good engineer would take. "Tells you when they cannot answer" is not what a good engineer does. They may say "I cannot answer question as-is" as a jump off for clarification. In fact in my response to your sibling comment I explain that even if there were no interesting bugs you can give an answer that isn't lying, or pulling engineering out of your ass, or dishonest. - But flat out refusing or immediately jumping to "well but I can't remember everything!!!!" is still you interpreting subtext... except you've now interpreted the most negative possible subtext. You've assumed your interviewer is asking you to recall things you can't recall and that there is no further room for discussion. A poor engineer is one that shuts completely down at the first hint of a broken invariant, rather than trying to surface that there is an invalid invariant, or learn more about the broken invariant. That kind of curiosity to go further than shutting down is what the question is meant to tease out, so you're not beating the system by deciding not to engage, instead you're sending the exact signal being looked for as something to avoid bringing into your organization.
jack_pp 4y ago
Exactly, I've been programming for a long time, almost 13 years since I started working on complex software and that question just makes me draw a blank. There's been bugs in my career but none that have "traumatized" me or been all that complicated to get through. Maybe I just don't put that much emphasis on negative experiences. I don't remember losing poker hands all that accurately either, I just don't care. Also if you've only ever worked in web dev or something easy like that are there even that many really "weird" bugs anymore? Maybe if you work on embedded or low level code bases with lots of race conditions.. those could qualify but if you're doing high level work.. that's rare
- teaearlgraycold 4y ago
  Working with Rails I learned, after much hair loss, that Class.new is a memory leak. So it can happen in high level languages, too.
- ThrustVectoring 4y ago
  Web dev still has tons of weird bugs, tend to be in the interactions between multiple frameworks and edge cases in the assumptions they make. Like, I had one issue with intermittent test failures in Ruby on Rails, not reproducible with any fixed seed, and not affecting production. The overall source of it was: 1. We had a table from a third-party API that used their ID as a primary key, I believe stored as a string. 2. Ruby on Rails believed that it should make sure that primary keys aren't a too-large-to-store integer before attempting to save a row. 3. Our test suite would generate fake hexadecimal strings for the primary key for testing purposes for the table. 4. Sometimes, the hexadecimal string would have enough leading 0-9 digits that when Rails coerced it to an integer for their own internal checks, it would exceed the integer limit it thought the table ought to have. I honestly only figured it out by getting lucky.
josephg 4y ago
Its an interview question. If you draw a blank on that, rephrase the question for yourself to something like this: "When you think of bugs you've recently fixed in your code, what comes to mind? Which bug had the most interesting story?". If that feels illegal to you, you can check with your interviewer: "I can't remember many weird old bugs, but can I tell you about a bug I fixed the other week?". Interviews aren't like tests in school. The point isn't to demonstrate knowledge. The point is to demonstrate to the interviewer that you're someone they'd want to work with. What are they looking for? They want someone they can trust technically, and someone they would enjoy working alongside. This question is great because its an opportunity to demonstrate both of those skills, by asking you to tell a story (social skills) about an experience you had programming. Use it!
- ryanjshaw 4y ago
  I fix plenty of weird bugs. But I don't build a reverse index in my mind of "weird bugs".
  - esperent 4y ago
    Can you think of any bug from that last five months that you could talk about for five minutes in a way that makes you look smart for solving it? That's all you need to do here.
    - josephg 4y ago
      You don’t even need a bug where you look smart for solving it. Eg, as an interviewer I also love stories that go like this: “There was this memory leak in some C++ code that took us weeks to track down that I’m still kicking myself for not finding earlier. It was totally my fault. Let me tell you what happened … … So the moral of the story is -fsanitize=address is smarter than me. But wow did I learn a lot about my tools from that.”
    - ryanjshaw 4y ago
      No, my mind goes completely blank. There's nothing wrong with my memory - I can tell you how I patched the timed Grand Theft Auto 1 demo over 25 years ago with SoftICE as a kid, but I assume my brain finds no value in tracking bugs.
thefourthchime 4y ago
Part of the process is going over your own history and making a collection of stories about what you've done and having that ready. I've shipped over a dozen products in my 25+ years. I can't recall much of any of it off-hand.
javierluraschi 4y ago
Me to ChatGPT: reply to this interview question "What's the weirdest bug you debugged? What made it weird?" in first-person, make it a personal story. ChatGPT: It was early on in my career as a software developer, and I was working on a web application that was designed to allow users to upload images and apply filters to them. One day, a user reported a strange issue where some of the filters were producing unexpected results. Specifically, they were seeing images that appeared to be completely random and unrelated to the original image. At first, I assumed it was a problem with the filter algorithms, but as I dug deeper, I realized that the issue was actually caused by a very strange bug. It turned out that the user's browser was caching a previously uploaded image and reusing it for subsequent filter operations, even if the user had selected a completely different image. This led to some very bizarre and unexpected results, as the filter algorithms were being applied to an entirely different image than what the user intended. To fix the bug, I had to implement a workaround that forced the browser to always load the most recent version of the image from the server, rather than relying on its cache. It was definitely one of the weirdest bugs I've ever encountered, and it taught me the importance of always being vigilant when it comes to caching and browser behavior. Me to ChatGPT: reply to this interview question "What's the weirdest bug you debugged? What made it weird?" in first-person, make it a personal story, make it using C++. ChatGPT: I was working on a project that involved developing a custom compiler. One day, a user reported a very strange issue where the compiled program would crash whenever it encountered certain input files. At first, I assumed it was a problem with the input files themselves, but as I dug deeper, I realized that the issue was actually caused by a very strange bug in the compiler code. It turned out that there was a subtle error in one of the class definitions that was causing memory corruption in certain circumstances. Specifically, the class had a virtual destructor, but the derived class failed to declare its own destructor as virtual. This led to undefined behavior when deleting objects of the derived class, which in turn caused the program to crash. To fix the bug, I had to carefully analyze the affected class definitions and make sure that all derived classes properly declared their destructors as virtual. It was definitely one of the weirdest bugs I've ever encountered, and it taught me the importance of paying close attention to class hierarchies and virtual functions in C++. Me to ChatGPT (since I haven't worked on a compiler): reply to this interview question "What's the weirdest bug you debugged? What made it weird?" in first-person, make it a personal story, make it using C++ about the time when I ported PyTorch from Python to R. ChatGPT: One of the weirdest bugs I encountered was during my work on porting PyTorch from Python to R. One of the major challenges was ensuring that the R implementation matched the performance and functionality of the Python version. As I was going through the codebase, I noticed a particularly strange issue that was causing crashes in the R implementation. The issue turned out to be related to differences in how Python and R handle memory allocation and deallocation. PyTorch relied heavily on dynamically allocated memory, but the R implementation was not properly managing this memory, leading to crashes and other unexpected behavior. To fix the issue, I had to go through the entire codebase and carefully analyze all memory-related operations. This involved a lot of debugging and experimentation, as well as close collaboration with the rest of the development team. Ultimately, we were able to resolve the issue and deliver a stable and performant port of PyTorch to R. It was definitely one of the weirdest bugs I've ever encountered, and it taught me the importance of paying close attention to memory management in C++ and other low-level languages. Note: Likely ChatGPT can also generate a fake resume, etc. so yeah.
taneq 4y ago
If you don’t have at least a couple of weird enough debugging war stories to still remember years later, you probably don’t have very broad debugging experience. (Not to say you aren’t a good developer, but you haven’t seen a lot of weird edge cases.)
- ryanjshaw 4y ago
  You're generalising how your brain works to how everybody's brain work. My brain doesn't respond well to questions out of nowhere. I don't maintain a "weird bugs" index. If we are just talking and something comes up there is a good chance I will have a related story, though.

hiq 4y ago

It doesn't have to be true though, it just has to be a nice story. And this is the kind of interview questions you can prepare.

epicureanideal 4y ago
> It doesn't have to be true though ... This is exactly why it's a bad question.

Swizec 4y ago

Can’t have been that good a bug, if you can’t. Been close to 15 years since some of the horror stories I can tell. Hell, over 20 years for some of my favorite lessons. edit: Point is the good shit stays. You’ll remember the best stories, fear not.

hgsgm 4y ago
When you get older, other memories crowd out specific bugs. Memory is associative. The father you are from the bug, the harder it is to remember. More importantly, you don't need to remember your own bugs, you can get a story from the Internet or ChatGPT.

BoorishBears 4y ago

I would 100% accept that as an answer since it tells me the candidate is not good with subtext, and that's really needed to solve a lot of interesting problems. After all, if I ask "what's your favorite food you've ever eaten", there's an unspoken implication that it's a food you remember eating. I am not in fact asking you to recall every single food you've ever eaten and choose one... - From my comment below since every reply seems to be bent on ignoring the subtext even in a theoretical discussion about picking up subtext...: Again, the subtext is "interesting example we're going to discuss". If there's one you can't discuss for any reason (doesn't even have to be you forgot: could be an NDA) then it's already excused from the discussion. An even half-decent interview is not adversarial: just like day to day work, it requires interpreting some level of useful subtext and some level of open communication - I mean, you forgot the details so it's not like it's not like you're going to start monologuing if you just touch on it: "You know, there's a real doozy from X years ago where Y but the details escape me, more recently Z happened" If there are none that you remember that are interesting: "There aren't many interesting bugs, but there was this really interesting product requirement, could we go over that?"

testTED 4y ago
But you are asking for the most interesting example, which you may remember from context, but not in any interesting or even technical detail.
- BoorishBears 4y ago
  Again, the subtext is "interesting example we're going to discuss". If there's one you can't discuss for any reason (doesn't even have to be you forgot: could be an NDA) then it's already excused from the discussion. An even half-decent interview is not adversarial: just like day to day work, it requires interpreting some level of useful subtext and some level of open communication - I mean, you forgot the details so it's not like it's not like you're going to start monologuing if you just touch on it: "You know, there's a real doozy from X years ago where Y but the details escape me, more recently Z happened" If there are none that you remember that are interesting: "There aren't many interesting bugs, but there was this really interesting product requirement, could we go over that?"
neilv 4y ago
> I would 100% accept that as an answer since it tells me the candidate is not good with subtext, [...] if I ask "what's your favorite food you've ever eaten", there's an unspoken implication that it's a food you remember eating. Will this filter cut many of the best engineers? Our field is full of people who pull 'engineering' out of our behinds, to various degrees. I'd assert that the engineer who doesn't assume an unspoken implication, but instead qualifies their answer, or tells you when they cannot answer, or asks for clarification... is more likely to be the one who can make a system that works, and tell you when a system will not work.
- BoorishBears 4y ago
  > Will this filter cut many of the best engineers? It won't cut out a single good engineer, let alone the best. > I'd assert that the engineer who doesn't assume an unspoken implication, but instead qualifies their answer, or tells you when they cannot answer, or asks for clarification... is more likely to be the one who can make a system that works, and tell you when a system will not work. You grouped the one option that a bad engineer would take, with several that a good engineer would take. "Tells you when they cannot answer" is not what a good engineer does. They may say "I cannot answer question as-is" as a jump off for clarification. In fact in my response to your sibling comment I explain that even if there were no interesting bugs you can give an answer that isn't lying, or pulling engineering out of your ass, or dishonest. - But flat out refusing or immediately jumping to "well but I can't remember everything!!!!" is still you interpreting subtext... except you've now interpreted the most negative possible subtext. You've assumed your interviewer is asking you to recall things you can't recall and that there is no further room for discussion. A poor engineer is one that shuts completely down at the first hint of a broken invariant, rather than trying to surface that there is an invalid invariant, or learn more about the broken invariant. That kind of curiosity to go further than shutting down is what the question is meant to tease out, so you're not beating the system by deciding not to engage, instead you're sending the exact signal being looked for as something to avoid bringing into your organization.

jack_pp 4y ago

Exactly, I've been programming for a long time, almost 13 years since I started working on complex software and that question just makes me draw a blank. There's been bugs in my career but none that have "traumatized" me or been all that complicated to get through. Maybe I just don't put that much emphasis on negative experiences. I don't remember losing poker hands all that accurately either, I just don't care. Also if you've only ever worked in web dev or something easy like that are there even that many really "weird" bugs anymore? Maybe if you work on embedded or low level code bases with lots of race conditions.. those could qualify but if you're doing high level work.. that's rare

teaearlgraycold 4y ago
Working with Rails I learned, after much hair loss, that Class.new is a memory leak. So it can happen in high level languages, too.
ThrustVectoring 4y ago
Web dev still has tons of weird bugs, tend to be in the interactions between multiple frameworks and edge cases in the assumptions they make. Like, I had one issue with intermittent test failures in Ruby on Rails, not reproducible with any fixed seed, and not affecting production. The overall source of it was: 1. We had a table from a third-party API that used their ID as a primary key, I believe stored as a string. 2. Ruby on Rails believed that it should make sure that primary keys aren't a too-large-to-store integer before attempting to save a row. 3. Our test suite would generate fake hexadecimal strings for the primary key for testing purposes for the table. 4. Sometimes, the hexadecimal string would have enough leading 0-9 digits that when Rails coerced it to an integer for their own internal checks, it would exceed the integer limit it thought the table ought to have. I honestly only figured it out by getting lucky.

josephg 4y ago

Its an interview question. If you draw a blank on that, rephrase the question for yourself to something like this: "When you think of bugs you've recently fixed in your code, what comes to mind? Which bug had the most interesting story?". If that feels illegal to you, you can check with your interviewer: "I can't remember many weird old bugs, but can I tell you about a bug I fixed the other week?". Interviews aren't like tests in school. The point isn't to demonstrate knowledge. The point is to demonstrate to the interviewer that you're someone they'd want to work with. What are they looking for? They want someone they can trust technically, and someone they would enjoy working alongside. This question is great because its an opportunity to demonstrate both of those skills, by asking you to tell a story (social skills) about an experience you had programming. Use it!

ryanjshaw 4y ago
I fix plenty of weird bugs. But I don't build a reverse index in my mind of "weird bugs".
- esperent 4y ago
  Can you think of any bug from that last five months that you could talk about for five minutes in a way that makes you look smart for solving it? That's all you need to do here.
  - josephg 4y ago
    You don’t even need a bug where you look smart for solving it. Eg, as an interviewer I also love stories that go like this: “There was this memory leak in some C++ code that took us weeks to track down that I’m still kicking myself for not finding earlier. It was totally my fault. Let me tell you what happened … … So the moral of the story is -fsanitize=address is smarter than me. But wow did I learn a lot about my tools from that.”
  - ryanjshaw 4y ago
    No, my mind goes completely blank. There's nothing wrong with my memory - I can tell you how I patched the timed Grand Theft Auto 1 demo over 25 years ago with SoftICE as a kid, but I assume my brain finds no value in tracking bugs.

thefourthchime 4y ago

Part of the process is going over your own history and making a collection of stories about what you've done and having that ready. I've shipped over a dozen products in my 25+ years. I can't recall much of any of it off-hand.

javierluraschi 4y ago

Me to ChatGPT: reply to this interview question "What's the weirdest bug you debugged? What made it weird?" in first-person, make it a personal story. ChatGPT: It was early on in my career as a software developer, and I was working on a web application that was designed to allow users to upload images and apply filters to them. One day, a user reported a strange issue where some of the filters were producing unexpected results. Specifically, they were seeing images that appeared to be completely random and unrelated to the original image. At first, I assumed it was a problem with the filter algorithms, but as I dug deeper, I realized that the issue was actually caused by a very strange bug. It turned out that the user's browser was caching a previously uploaded image and reusing it for subsequent filter operations, even if the user had selected a completely different image. This led to some very bizarre and unexpected results, as the filter algorithms were being applied to an entirely different image than what the user intended. To fix the bug, I had to implement a workaround that forced the browser to always load the most recent version of the image from the server, rather than relying on its cache. It was definitely one of the weirdest bugs I've ever encountered, and it taught me the importance of always being vigilant when it comes to caching and browser behavior. Me to ChatGPT: reply to this interview question "What's the weirdest bug you debugged? What made it weird?" in first-person, make it a personal story, make it using C++. ChatGPT: I was working on a project that involved developing a custom compiler. One day, a user reported a very strange issue where the compiled program would crash whenever it encountered certain input files. At first, I assumed it was a problem with the input files themselves, but as I dug deeper, I realized that the issue was actually caused by a very strange bug in the compiler code. It turned out that there was a subtle error in one of the class definitions that was causing memory corruption in certain circumstances. Specifically, the class had a virtual destructor, but the derived class failed to declare its own destructor as virtual. This led to undefined behavior when deleting objects of the derived class, which in turn caused the program to crash. To fix the bug, I had to carefully analyze the affected class definitions and make sure that all derived classes properly declared their destructors as virtual. It was definitely one of the weirdest bugs I've ever encountered, and it taught me the importance of paying close attention to class hierarchies and virtual functions in C++. Me to ChatGPT (since I haven't worked on a compiler): reply to this interview question "What's the weirdest bug you debugged? What made it weird?" in first-person, make it a personal story, make it using C++ about the time when I ported PyTorch from Python to R. ChatGPT: One of the weirdest bugs I encountered was during my work on porting PyTorch from Python to R. One of the major challenges was ensuring that the R implementation matched the performance and functionality of the Python version. As I was going through the codebase, I noticed a particularly strange issue that was causing crashes in the R implementation. The issue turned out to be related to differences in how Python and R handle memory allocation and deallocation. PyTorch relied heavily on dynamically allocated memory, but the R implementation was not properly managing this memory, leading to crashes and other unexpected behavior. To fix the issue, I had to go through the entire codebase and carefully analyze all memory-related operations. This involved a lot of debugging and experimentation, as well as close collaboration with the rest of the development team. Ultimately, we were able to resolve the issue and deliver a stable and performant port of PyTorch to R. It was definitely one of the weirdest bugs I've ever encountered, and it taught me the importance of paying close attention to memory management in C++ and other low-level languages. Note: Likely ChatGPT can also generate a fake resume, etc. so yeah.

taneq 4y ago

If you don’t have at least a couple of weird enough debugging war stories to still remember years later, you probably don’t have very broad debugging experience. (Not to say you aren’t a good developer, but you haven’t seen a lot of weird edge cases.)

ryanjshaw 4y ago
You're generalising how your brain works to how everybody's brain work. My brain doesn't respond well to questions out of nowhere. I don't maintain a "weird bugs" index. If we are just talking and something comes up there is a good chance I will have a related story, though.