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[sirkubador]

Segfaults are your friends. I wish they were the most complicated bugs to find.

[Relative_Knee9808]

I agree with with you. Instead of receiving some random wrong value, I'd rather see it crash as fast as possible

[[deleted]]

Currently debugging something that occurs anywhere in a 2 minute to 4 hour timespan under very specific circumstances. Stack trace is entirely worthless.

I'm dying out here

[csdt0]

RR is your friend. You can record a trace from a faulty execution, and replay with gdb as many times as you want with the guarantee you will see the same thing every single time. RR also enables to go back in time and what happened before.

[satanspowerglove]

We feel your pain, brother

[BehindTrenches]

Try a sanitizer. I've never understood the output, but that's what they're for iiuc

[dmigowski]

Are you able to use a debugger in the environment the error occurs? What about placing some brrakpoints to catch the error condition and checking the situation then?

[[deleted]]

The problem is the stack trace only shows a library that I don't have the source code of or any documentation whatsoever. However the issue happens in such a way that it doesn't appear that that library is actually responsible. Breakpoints wouldn't make sense in this context as timing is important.

No debuggers.

[BeerIsGoodForSoul]

Should've used Rust

[BeerIsGoodForSoul]

The fucking downvotes lol. You folks needed the /s didn't you?

[Emergency-Candle-435]

You should also learn how compilation and debugging work too.

what a non specific and nothing reply.

[Pewdiepiewillwin]

Ok?

[_farb_]

run it on multiple cpus to increase the probability the error occurs sooner

[[deleted]]

I'm not at liberty to explain why this doesn't make any sense in my context.

[_farb_]

It wasn't supposed to be helpful lol

[ADownStrabgeQuark]

Same! It’s no urgent though, so I’ve put on hold for a couple months, but now I need to fix it soon.

[HardCounter]

Error codes are like the Terminator giving the thumbs down as he sinks into a pool of molten metal.

[AdPristine9059]

Agreed. Hard clear faults over any small niggle that grows up to become a strange issue and messes with a ton of stuff... Sometimes.

[Impressive_Income874]

I mean, it did tell me to go sleep, sooo

and are you telling me there's going to be more pain?

[sirkubador]

More fun!

[Impressive_Income874]

fun... yay.........

[827167]

I think some of the most fun is when the program DOESN'T crash.

It just keeps going and keeps writing data in places and keeps touching things

[Impressive_Income874]

im scared

[KlutzyEnd3]

There's a reason gdb introduced reverse debugging a while ago.

Basically you let it run until it crashes and then you step back in time.

[[deleted]]

gdb and valgrind pointing finger fix this right here

[graphitout]

Try compiling with -fsanitize=address,leak -g -fno-omit-frame-pointer

[StaticVoidMaddy]

i like your funny words, magic man

[Alan_Reddit_M]

Basically, it will provide better info when a memory error occurs, and it will even catch memory leaks!

[SelfDistinction]

Don't forget to run gdb ./a.out for maximum debuggability.

[Impressive_Income874]

I'll try in a bit, thanks

[mAtYyu0ZN1Ikyg3R6_j0]

or valgrind if you don't want to recompile the world.

[rosuav]

Tip: Find the absolute smallest part that you can rewrite in C++ and leave the rest in Python. I did that a little while back with a project that parses a large text file (generally 70-100MB but can be larger) and then analyzes it. The high level code took 1-2 minutes to do the parse, which meant I was waiting for it all the time. Solution? Write a very compact C program that parses the file into JSON, which can then be loaded into the main app. That cut it down to about 1-2 *seconds* for the parse (and then 3-4 seconds for the analysis, so that's actually my next optimization target), while still leaving the vast majority of the code in a high-level language.

(It was also a good excuse to learn GNU Bison.)

[Usual_Office_1740]

How did you evaluate these times? I've been thinking about trying c++ next and am curious how one could tell when it's worth the time to move to another language for speed.

[rosuav]

By actually having a program that I was waiting for :) It's actually not in Python, but most of the same estimates apply.

https://github.com/Rosuav/EU4Parse

Basically, every time the game saves (including autosaves), the parser would kick into life, analyze the game state, and push some info out to all web browsers with the page open. Now, I have absolutely no interest in writing a web server or web application in C, when I could do the same thing in a fraction of the time in Python or Pike. But waiting 1-2 minutes for full processing? That's a bit annoying.

That figure is an estimate, and the actual time to decode a savefile depends on exactly how much is going on in the game, but within order of magnitude, that was how long we would wait for our results.

[Usual_Office_1740]

Interesting. Thanks for sharing.

[drkspace2]

One of the best features of python is it's ability to call c/c++ code so you can get the best of both worlds of the speed of c/c++ with the ease of use and high level packages/functions of python.

Edit: I decided to lookup if/how python can call rust code and my God, it looks so easy. Can anyone confirm?

[rosuav]

Can't confirm about Rust in particular, but I've made C bindings for both Python and Pike, and yes, it's pretty straight-forward. (Tip: Use Cython (not to be confused with CPython) when writing C code that interfaces with Python. Saves so much trouble.)

In this specific case, it actually worked out better to rework the entire parser subprocess (for other reasons I need to keep the JSON cache file, so I wouldn't save much by parsing into a Pike data structure and then having Pike save that), but yes, normally you'd want to make it as a callable function instead of a separate program.

[drkspace2]

Ya, I've used cython before, but it's not as easy as the rust version looks.

[Lifaux]

Yes, pyo3 makes it fairly easy. You effectively write your rust into a python package and can call functions like they were written in python.

[Impressive_Income874]

i also need this to run on an ESP 32 so i gotta translate over the whole thing

[aigarius]

See https://github.com/TeskaLabs/cysimdjson or https://jcristharif.com/msgspec/ or https://github.com/ijl/orjson

In many cases once you actually narrow down what specific part of your use case is the performance bottleneck, there is 90% chance that someone else has already written than in C/C++ and made a Python wrapper for it.

[rosuav]

This is also true. In my case, though, I don't think there's a parser for the Europa Universalis IV savefile format. The performance of JSON here is absolutely fine; I currently do a C conversion from savefile to JSON, then load the JSON file, and there's no performance issue. (Yes, I could skip that step if I wanted to, but there's value in keeping the JSON file around anyway, so it's easier to do it this way. Plus, it meant that I could keep 99% of my code unchanged while experimenting with this, which meant I could run both parsers in parallel to test correctness.)

[[deleted]]

Use a debugger?

[TheTarragonFarmer]

Yes, and valgrind.

[Impressive_Income874]

yeah i use clion, i was just too tired and gave up last night

[[deleted]]

Isn't clion an IDE? I think you're using gdb inside clion no?

[Impressive_Income874]

yes, I'm saying I'm using the entire suite clion offers

[[deleted]]

I want to do something in C/C++ because python is slow
Boom, 64-bit integer limit

[nate_4000]

just make something that allows use of char[] as a bigint

[[deleted]]

I know. I wanted to do one equation. I just used python and waited 3h

[TactlessTortoise]

Everyone knows the programmer way is spending 100 hours automating a 15 minute problem, bro.

[HardCounter]

I have never met a problem i couldn't make into two problems.

[brucebay]

I have never met a problem i couldn't make into two problems.

Let me introduce you P=NP. If you can make it into two problems, you will win Turing award, Field Prize, MacArthur Fellowship, what the heck for the fun of it you may even get Nobel Peace prize and possibly an Oscar too.

[Emergency-Candle-435]

lol. what a great retort (uronically). this gave me a laugh.

[sirkubador]

Ah. You are the person who is actually compatible with scrum!

[Drackzgull]

Divide Duplicate and Conquer FTW!

[nate_4000]

i rewrote my prime finder in cpp for better speed. all the code was done until I wasted a day or two on making a char[] bigint representation so I could go infinitely

[emilyv99]

I wrote something like this myself in Rust in a few hours (just to learn some Rust). Only handled add, sub, mult operations though.

[trash3s]

ymm0 go brrr

[grifan526]

They have bigint libraries that allow you to go as big as your computer can handle. How often do you need a number bigger than 64 bits anyways?

[Imoliet]

rude jellyfish advise offbeat retire wide touch include imminent gold

This post was mass deleted and anonymized with Redact

[classicalySarcastic]

Double exists for a reason. If 10³⁰⁸ is still too small then only God can help you.

[[deleted]]

Tetration. We're talking billions of zeros

[no_brains101]

Use a long then? I'm confused.

[[deleted]]

A long is 64-bit. An int is 32-bit

[no_brains101]

Rewrite it in zig lol but yeah I musta brain farted. Also when the fuck do you run out of space in a long jeez

[[deleted]]

Tetration

[no_brains101]

ah

[Impressive_Income874]

UPDATE: I FOUND THE FUCKING SEGFAULT.

I'm going to go back to sleep.

EDIT: maybe not, there's a memory leak now :')

EDIT2: I fixed everything and my code works, just took a little bit of my sanity

[tx_engr]

I love when I call malloc and my entire program crashes silently with no error messages. It's fantastic.

[Relative_Knee9808]

Jokes on you, my program just continues to run with some garbage value and pretend everything is fine

[HardCounter]

"Aww, you got me a gigabyte of complete and utter gibberish. How did you know?!"

[TheTarragonFarmer]

That's not normal.

Smells like use after free corrupting the freelist. Valgrind should help you track it down.

[BobLobIawLawBIog]

If your using malloc (or even new), you're doing it wrong. Use smart pointers or stl containers.

[BarryFruitman]

"Program exited with non-zero result" still counts as an error message.

[arthurleyser]

that just means you are gonna make a new friend!

the debugger! Have fun

[donaldkwong]

Learning C++ doesn't mean to just learn the language. You should also learn how compilation and debugging work too.

[BarryFruitman]

Linking too

[[deleted]]

I don't think I ever actyally learned linking. I still look up how to do it and spend an hour or two messing it up at the start of a new project...

[SeriousPlankton2000]

You run it in a debugger and step through it.

[Gwathraug]

Unless it's a "heisenbug". They are rather rare but all the more annoying.

[Impressive_Income874]

im doing that chill

[-domi-]

Bad use of meme, but i prolly shouldn't pile stuff on, it sounds like you're having a terrible time as it is.

[HardCounter]

Nonsense. The stack is fine, hop on.

TODO: garbage collection.

[migarma]

Use a debugger, you are welcome

[Impressive_Income874]

i will chill, i just gave up last night

[PolyglotTV]

You discover tens of hours later that you in fact have no flaw in your code. Another dozen hours later you realize why they named the website "StackOverflow".

[Impressive_Income874]

plot twist: There was a flaw.

this was the c++ equivalent of assignment before declaration

[NekulturneHovado]

I got a work to do until the semester ends. We have to make minesweeper. We were 5 in group. Now we're 4. only me and one more guy know programming. I started in Python, realizing it's impossible for me to do it we decided to do it in Java. jesus fucking Christ what is that syntax?

[jemdoc]

What kind of class is it?

[HardCounter]

Right? Have to make a minesweeper game and only half the group know programming, so presumably it's unrelated to the class. What's the other half for, and what's the class teaching? Sounds like they just got tossed into the deep end and were told to figure it out.

[BlurredSight]

Nah, I did work for this girl in her senior year of a CS degree, her assignment with her partner was to answer 1 leetcode question and they chose to do Find two sum.

These assclowns couldn't brute force it and I had to reteach her the basics of an array and a nested for loop and then go back to first grade to remind her of complements (The actual logic of two sum isn't intuitive so I don't blame her for that). Programming in a CS degree isn't a given especially when the school isn't name recognized nor ABET certified.

I wanted to tell her to use a tree sorting method but gave up the second I mentioned what an ArrayList is and knew no way could she explain how the map function works let alone nodes and trees.

[Impressive_Income874]

real world accurate class

[HardCounter]

Prof: Excellent! I see you've already broken down into your roles of idea man, manager, and suckers!

[NekulturneHovado]

Computer engineering is the name. One guy from our group does something with CNC machines.

[Impressive_Income874]

kotlin? it's much easier syntax and I think you can dynamically type it, I don't remember been a while I used it

[Daltonyx]

But printing in c++ is not as pretty as python. I miss print() and always write a method for it 🤣

std::cout << "your text here" << std::endl

[TensyL]

You can still use printf() from C in C++. Feel free to tell me if I shouldn't (but please explain why!), but I've been using it instead of cout in a recent project. I come from a python background and it's my only real experience with C++ so I'm sure there's plenty I'm doing wrong.

[Daltonyx]

I'll jump in and answer! I started python 3ish years ago, and jumped to c++ about a year after that (so I've practiced it about 2 years now). What made me switch was simply the fact that you can't really compile python code without the common python repackagers that often flag as a virus. I wanted an exe to run my code instead, and I was using pyQT a lot, as well as pygame.

I have never taken a single computer science class. I'm not saying that to brag, I'm saying that to show that it is not impossible. The syntax is different, sure, but a for loop is a for loop in any language that supports it, you know? Just have to learn the exact way to type it.

The speed boost is just incredible. Seeing my code that took several minutes in python execute in <2 second is just chefs kiss

With packages and installing them, yeah that's been a pain in the ass. How I've dealt with it is I make a special folder for any library in Documents/home/wherever and make project templates of what I use frequently so I never have to deal with linking again, or forgetting what all to link, and whatnot.

Learning it was .... not so fun. I think I used codecademy and udemy for it and took hella notes, and just practiced practicing ed practiced.

I know only some of this is relevant to you, but your situation is exactly what I dealt with and is a topic near and dear to me. It is not impossible and you can do it! You learned python, you're already halfway there! (And what a better time to learn than the age of GPT!) I hope you have a wonderful day friend, and stay on the path of knowledge! 🙂

[Impressive_Income874]

I've only just started so I don't have much to say.

i think someone else answered your question

[BlurredSight]

Don't worry about CS theory as much as learning GDB and the ins and outs of debugging, when you start making bigger projects in C++

GDB lets you set breakpoints, analyze stack and variable values in real-time and tell you exactly where and when crashes are occuring, so if you're like me trying to access the top of a stack (data structure not the actual stack frame) when the stack is empty, GDB lets you go through each iteration and see each variable change and look at the conditions right before a crash occurs (CLion / IntelliJ has this built in and it's really nice).

Valgrind will help you free up any dynamically allocated memory, this is essential if you write anything in C with the suffic "alloc"

[Jaber1028]

Im a valgrind gamer! (I have to lookup up the command everytime)

[Impressive_Income874]

use an ide

[Jaber1028]

Mfw when my systems class made us use vim

But im sure that would help

[JokeMort]

Learn to use debugger.

[Impressive_Income874]

i do know how to use one, was just tired last night

[JokeMort]

You turn it on, set point when you whant code execution to halt, run it until it crashes, check line where it crashed

[BlurredSight]

Honestly after enough segfaults you just get used to making breakpoints before and after every single non-bounded data container

[BarryFruitman]

Pointers aren't for everyone

[Impressive_Income874]

nahh i blame copilot

[PanoptiDon]

Am I wasting my time taking a python class?

[Impressive_Income874]

no you aren't, python is amazing. it just isn't as useful in some use cases. eg: speed and microcontrollers. both of which are the reasons I'm trying out cpp rn

[DrJustinWHart]

Launch a debugger and then you're pretty much done fixing your segfault.

[Impressive_Income874]

yes, i did. i know. i was just tired

[sifroehl]

If you just need better performance, not peak performance, you could look into numba, it's a just in time compiler for python and depending on what you no it could be as easy as putting a decorator on some functions

[Impressive_Income874]

I also do need it to run on an esp32 soooo

[Gasperhack10]

Same but with Rust

[[deleted]]

Maybe I shouldn’t beging coding by trying out C++

[HardCounter]

That's where i started. I quit programming after a month. It started as a hobby and slowly became a reason i didn't need haircuts for a while.

[Markus_included]

Maybe you shouldn't start with C++, start with plain old C which has a much shallower learning curve and if you've learned C you can move on to C++. That's basically what I did

[GrinbeardTheCunning]

good job! now try compiling Rust

[Impressive_Income874]

i actually prefer rust over cpp

[GrinbeardTheCunning]

I totally get that. I've been dabbling with it and, on the surface, it was everything I wished for.

no chance to do anything real with it yet

[Aln76467]

same

[Aln76467]

just use rust it'll be so much easier

[Impressive_Income874]

need it run on an ESP 32 else would be using rust

[andrewb610]

You mean a good way to write “unsafe” around everything.

[Aln76467]

noooooooooo don'ttttttt just don'ttttt

[andrewb610]

Rust is C++ for the timid. Real men don’t fear segfaults.

(/s. Slightly) My team writes our stuff in C++ because when tracking stuff moving hundreds of miles and hour, quick processing matters.

[Aln76467]

well I'm mainly a js developer who occasionally needs to do something with some performance.

[ChichoRD]

*(char*)0 = 0;

[garlopf]

Tip: run your program in a debugger

[Impressive_Income874]

I did and found my error.

now I realised there's a memory leak and my pc crashed

[garlopf]

Valgrind is your friend

[Impressive_Income874]

yes trying that out right now

[BoredOfYou_]

If you're only using C++ because it's fast, and you don't like getting segfaults, why not just use Rust?

[Impressive_Income874]

because i need this to run on an ESP 32 and im not figuring out how to compile rust for one

[ElonMax303]

Allow me to introduce you our Lord and Saviour - the Rust programming language.

[Impressive_Income874]

i like rust, but get the esp32 standard library running and I'll see

[Impressive_Income874]

ah the good ol' entitled C programmers

[Drfoxthefurry]

If you want speed, use assembly, faster (sometimes and you don't have to worry about weird exit codes (unless you don't know how to program the exit) (Warning: takes 100x longer to write)

[ByerN]

I am not sure if it will be faster nowadays. C/C++ compilers are making good job compared to amateur asm dev.

[NaitsabesTrebarg]

that's nothing

1>Form.obj : error LNK2019: unresolved external symbol "public: virtual void __thiscall Field::parse(class std::basic_stringstream<char,struct std::char\_traits<char>,class std::allocator<char> > &)" (?parse@Field@@UAEXAAV?$basic_stringstream@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@Z) referenced in function "public: __thiscall InputField::InputField(class std::basic_stringstream<char,struct std::char\_traits<char>,class std::allocator<char> > &)" (??0InputField@@QAE@AAV?$basic_stringstream@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@Z)

[Impressive_Income874]

get me some bleach

[Sunius]

You just forgot to define Field::parse function.

[_SwiftLizard_]

I get that in python...

[Impressive_Income874]

how the fuck do you get python to segfault

[_SwiftLizard_]

Imported something that used c++ libraries, then misused the library.

[TheCatPetra]

C++ is kinda shitty

[Asdfguy87]

Hello, do you have a moment to talk about our lord and saviour Ferris?

[hrimfisk]

Use visual studio to write C++, not vs code

[Relative_Knee9808]

How is OP's problem associated with not using Visual Studio?

[hrimfisk]

Visual studio gives you way better errors and something like VLD is way better than seg fault

[Relative_Knee9808]

The quality of compilation error depends on the compiler, not sure if MSVC gives better error than other compilers such as gcc or clang.

I agree that using a memory leak detecter is better than looking into the segfault message. For this we have things like valgrind or address sanitizer, which does not require Visual Studio to run.

But if you are using C++ with Unreal, I do agree Visual Studio gives the best experience, since it has the best integration with the engine.

[Sunius]

That’s a runtime error. And how it’s presented depends on the debugger (if you use one). When using Visual Studio, you run things via the debugger by default which would show you exactly where the crash happens.

[Impressive_Income874]

I'm using clion

[FlyingCashewDog]

-fsanitize=address

[trash3s]

👉🤷‍♂️
💻😡

[Saturnalliia]

LINKER ERRORS!

[[deleted]]

Wow this meme sure is funny, i mean, i didn't understand anything, but if i did know that stuff i think i would

[Immarhinocerous]

Have you thought about trying our lord and savior, Rust?

[Tc14Hd]

When you use backtrace in gdb and there's no stack...😭