4 ms·

A log is very different than a debugger though, one tells you what happened, one shows you the entire state and doesn't make you assemble it in your head.

by hobs 1y ago

demosthanos 1y ago
Your framing makes it sound like the log is worse in some way, but what the log gives you that the debugger makes you assemble in your head is a timeline of when things happen. Being able to see time is a pretty big benefit for most types of software. I can always drop an entire state object into the log if I need it, but the only way for a debugger to approximate what a log can give me is for me to step through a bunch of break points and hold the time stream in my head. The one place where a debugger is straight up better is if I know exactly which unit of code is failing and that unit has complicated logic that is worth stepping through line by line. That's what they were designed for, and they're very useful for that, but it's also not the most common kind of troubleshooting I run into.
- hobs 1y ago
  It's not worse or better, but its not really comparable is all I am really saying, I would not use them for the same things.
- switchbak 1y ago
  In the early 2000’s I whipped up a tool to convert log statements into visual swim lanes like the Chrome profiler does. That thing was a godsend for reasoning about complex parallelism.
  - EFreethought 1y ago
    Would you be willing to share this tool?
    - switchbak 1y ago
      Oh that's long lost to the trashbin of history. As I recall it was a combination of: - Log4j + MDC's so we could get a timestamp and thread ID easily - some python scripting I can't remember if it was PDF or SVG, but I do remember having to choose something that would allow for huge graphs and lots of scrolling! These days there's better options on github, but nice to see I was on a decent path.
fingerlocks 1y ago
All these print debugging advocates are blowing my mind. Are most people unaware that both lldb and gdb have conditional pass throughout breakpoints with function hooks? In other words, you can create a breakpoint that just prints its location and doesn’t pause execution. You can script this so all function entry/exists, or whatever, are logged without touching the code or needing to recompile. You can then bulk toggle these breakpoints, at runtime, so you only see a particular subset when things get interesting. Modifying the code to print stuff will feel barbaric after driving around a fine tuned debugging experience.
- dpkirchner 1y ago
  I can't tell you how many times lldb has failed to hit breakpoints or has dumped me in some library without symbols. This was in Xcode while writing an iOS app, maybe it's better in other environments. Print debugging, while not clever or powerful, has never once failed me.
  - fingerlocks 1y ago
    Sometimes the debugserver is flakey, I’ll give you that. But some that also sounds like UI quirks such as ambiguous breakpoints on a function definition with default initialized default values. You can attach lldb without Xcode. Or you can open the lldb terminal in Xcode, pause execution, and inspect the breakpoints manually
mort96 1y ago
I've never had a debugger show me the entire state. I'm not even sure I want to know the entire state, but GDB has a lot of issue with anything but the most basic data structures most of the time, and I always need to explicitly ask for what I want to see by calling things like operator[] (and then hope that the particular operator[] wasn't optimized out of the final binary). It's not exactly a great experience.

A log is very different than a debugger though, one tells you what happened, one shows you the entire state and doesn't make you assemble it in your head.

by hobs 1y ago

A log is very different than a debugger though, one tells you what happened, one shows you the entire state and doesn't make you assemble it in your head.

demosthanos 1y ago

Your framing makes it sound like the log is worse in some way, but what the log gives you that the debugger makes you assemble in your head is a timeline of when things happen. Being able to see time is a pretty big benefit for most types of software. I can always drop an entire state object into the log if I need it, but the only way for a debugger to approximate what a log can give me is for me to step through a bunch of break points and hold the time stream in my head. The one place where a debugger is straight up better is if I know exactly which unit of code is failing and that unit has complicated logic that is worth stepping through line by line. That's what they were designed for, and they're very useful for that, but it's also not the most common kind of troubleshooting I run into.

hobs 1y ago
It's not worse or better, but its not really comparable is all I am really saying, I would not use them for the same things.
switchbak 1y ago
In the early 2000’s I whipped up a tool to convert log statements into visual swim lanes like the Chrome profiler does. That thing was a godsend for reasoning about complex parallelism.
- EFreethought 1y ago
  Would you be willing to share this tool?
  - switchbak 1y ago
    Oh that's long lost to the trashbin of history. As I recall it was a combination of: - Log4j + MDC's so we could get a timestamp and thread ID easily - some python scripting I can't remember if it was PDF or SVG, but I do remember having to choose something that would allow for huge graphs and lots of scrolling! These days there's better options on github, but nice to see I was on a decent path.

fingerlocks 1y ago

All these print debugging advocates are blowing my mind. Are most people unaware that both lldb and gdb have conditional pass throughout breakpoints with function hooks? In other words, you can create a breakpoint that just prints its location and doesn’t pause execution. You can script this so all function entry/exists, or whatever, are logged without touching the code or needing to recompile. You can then bulk toggle these breakpoints, at runtime, so you only see a particular subset when things get interesting. Modifying the code to print stuff will feel barbaric after driving around a fine tuned debugging experience.

dpkirchner 1y ago
I can't tell you how many times lldb has failed to hit breakpoints or has dumped me in some library without symbols. This was in Xcode while writing an iOS app, maybe it's better in other environments. Print debugging, while not clever or powerful, has never once failed me.
- fingerlocks 1y ago
  Sometimes the debugserver is flakey, I’ll give you that. But some that also sounds like UI quirks such as ambiguous breakpoints on a function definition with default initialized default values. You can attach lldb without Xcode. Or you can open the lldb terminal in Xcode, pause execution, and inspect the breakpoints manually

mort96 1y ago

I've never had a debugger show me the entire state. I'm not even sure I want to know the entire state, but GDB has a lot of issue with anything but the most basic data structures most of the time, and I always need to explicitly ask for what I want to see by calling things like operator[] (and then hope that the particular operator[] wasn't optimized out of the final binary). It's not exactly a great experience.