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Compile time optimization
Is it possible to make gcc optimize static values at compile time?
I would expect for example | x=12+16;
to be optimized to | x=28; and it does.
but also. A lot of times all values needed are known at compile time.
int fibo(int n) {
if (n <= 1) return n;
else return fibo(n-2) + fibo(n-1);
}
int main() {
std::cout << fibo(40) << "\\n";
return 0;
}
​
There is nothing unknown with this small program. It will make the exact same calls to the OS print functions every time.
It should be able to optimize it to
int main() { std::cout << 102334155 << "\\n"; return 0;}
But that's not what happens. At least not when I try with gcc -o2 or -o3.
Can you make it even more aggressive? like an -o4
https://redd.it/1b9s38r
@r_cpp
El evento web del personaje Chiori «Cortes primorosos» de Genshin Impact ya está disponible.
https://sg-public-api.hoyoverse.com/event/social_sea_share/redirectUrl?key=m20240202hy37qrups0&lang=es-es&game_biz=hk4e_global&title_key=share_title&url=https%3A%2F%2Fact.hoyoverse.com%2Fys%2Fevent%2Fe20240308chiori-cuesme%2Findex.html%3Fgame_biz%3Dhk4e_global%26hyl_presentation_style%3Dfullscreen%26hyl_landscape%3Dtrue%26hyl_auth_required%3Dtrue%26hyl_hide_status_bar%3Dtrue%26utm_source%3Dshare%26utm_medium%3Dhoyolab%26utm_campaign%3Dapp&img_url=https%3A%2F%2Fact-upload.hoyoverse.com%2Fevent-ugc-review%2F2024%2F03%2F08%2F668835156%2Fbc9dc30521120115f843cc9bea385500_757577843997455242.jpeg&desc_key=share_desc&timeStamp=5699582
https://redd.it/1b9fy1r
@r_cpp
Lawfare: NIST's Software Un-Standards
https://www.lawfaremedia.org/article/nist%27s-software-un-standards
https://redd.it/1b9c62g
@r_cpp
I want to understand the Compatibility between QT/c++ versions
Hi,
I am a CS Uni student with an arm-based MacBook. I have set up QT Creator and did a test project on QT6. However, when I tested the environment in which our projects will be tested, it said, "Qt Creator 6.0.2 based on Qt 5.15.3." So my question is how much QT is backwards compatible in C++, and if not, what solutions can you give?
Thank You for Reading
https://redd.it/1b90f4h
@r_cpp
is there a better way to do this?
https://github.com/yaboytabby/simple-dice-game/blob/upd/shop.cpp
https://redd.it/1b8v4ps
@r_cpp
What are common mistakes in C++ code that results in huge performance penalties?
As title, list some common mistakes that you have done/seen which lead to performance penalties.
https://redd.it/1b8tmyb
@r_cpp
State of the Art Memory Allocators for C++
Guys, I am working on a project where memory allocation is the bottleneck for runtime with multithreaded code. I am planning to replace glibc implementation with other oper source alternatives. A basic Google search seems to indicate that tcmalloc and jemalloc are primary contenders. Is there any other open source alternatives that are deemed to be "state-of-the-art" and I should profile with my testcases?
https://redd.it/1b8qu79
@r_cpp
My late discovery of std::filesystem - Part II
https://www.sandordargo.com/blog/2024/03/06/std-filesystem-part2-iterate-over-directories
https://redd.it/1b8nx3m
@r_cpp
Prediction market: will "managing dependencies" still be one of the biggest pain points for the c++ community in 2028?
Hello everyone,
In the 2023 annual c++ global survey "lite" had "managing libraries my applications depend on" as the biggest pain point for the c++ community. https://isocpp.org/blog/2023/04/results-summary-2023-annual-cpp-developer-survey-lite
I looked at the 2018 survey and it still was one of the main pain points.
Will anything be different in 2028? I'm cautiously optimistic. There's the C++ ecosystem evolution group, ISO SG15, and tools like vcpkg and Conan are getting better (?).
But I don't know how much I would bet on it, and I'd like to hear what the community thinks, which is why I've created a prediction market about it on manifold to get bets on it https://manifold.markets/embed/braulios/will-the-2028-annual-c-survey-cite it's play money (I hope this is no considered spam, I'm not affiliated to manifold other than being a user and consulting prediction markets frequently). If people don't want to sign up on manifold (fair!) I'd also like to hear people's takes here
https://redd.it/1b8e0vj
@r_cpp
Conda as a package manager for cpp projects on Windows.
I've been doing some LLM work and running models with compiled cpp, it is pure bliss. However i'm using windows and find myself using conda to install dependencies. How many have used this? Its so easy I feel like I'm using a linux package manager. As I've not heard about it I suspect I might run into some pitfalls.
https://redd.it/1b8736z
@r_cpp
Exercise
Hey everyone. Need help. With this code. #include <iostream>
# include <fstream>
# include <iomanip>
# include <clocale>
# include <string>
using namespace std;
struct prekes {
string produktas;
int year, month, day, consumptiondays;
};
void reading(struct groceries x[\], int &quantity)
{
//const int length = 21;
//char s[length\]{};
ifstream file("groceries.txt");
failas >>quantity; failas.ignore(80, '\\n');
for (int i = 0; i < quantity; i++)
{
getline(file, x[i\].product); file.ignore(80, '\\n');
/*file.get(s, length);
x[i\].product = s; file.ignore(80, '\\n');*/
failas >> x[i\].year>>x[i\].month>>x[i\].day>>x[i\].consumptiondays; file.ignore(80, '\\n');
}
file.close();
}
int main()
{
setlocale(LC_ALL, "Lithuanian");
groceries x[100\];
string product;
int quantity;
reading(x, quantity);
for (int i = 0; i < quantity; i++)
{
cout << setw(21) << x[i\].product << left << x[i\].year<<" "<<x[i\].month<<" "<<x[i\].day<<" "<<x[i\].consumptiondays<< endl;
}
return 0;
}
The file is this one:
5 (this is the 'quantity' mentioned up above)
Virtos bulvės 2011 01 15 2
Mėgėjų salotos 2011 01 10 1
Sūris su aguonomis 2011 01 22 15
Duona su aguonomis 2010 12 20 20
Rauginti agurkai 2010 09 15 100 When I read from the file, it only shows me this:
Virtos bulvės 2011 01 15 20
-858993460
-858993460
-858993460
-858993460
I need help as I've only just started learning c++.
https://redd.it/1b7etfg
@r_cpp
Latest News From Upcoming C++ Conferences (03/05/2024)
Every two weeks this thread will be updated with the latest news from C++ events that are coming up:
# C++Online - https://cpponline.uk/
C++Online is an online only C++ conference is designed to provide a more accessible option for those who might find attending other in-person international conferences more difficult or financially restrictive.
Latest News: The main conference ran last week. However, there is still a one day Concurrency Workshop from Rainer Grimm on the 14th March that can be purchased at https://cpponline.uk/registration
\---
# ACCU - https://accuconference.org/
The ACCU Conference is a conference by programmers for programmers about programming with a strong focus on C++.
Workshops: Monday 15th & Tuesday 16th April
Main Conference: Wednesday 17th February - Saturday 20th February
Location Online & In-Person at Bristol, England
Registration: Early bird registration is now live and will end on 6th March! https://accuconference.org/pricing. Tickets for the full conference start from £895 + VAT (with student tickets being £195 + VAT) but are cheaper to ACCU members - so join up today if you're not already a member: https://accu.org/menu-overviews/membership/
Latest News:
After delays, ACCU have now released the full schedule for the conference (which includes the previously announced workshops) https://accuconference.org/2024/schedule
Because of the delays in releasing the schedule, Early Bird registration has been extended to end tomorrow (6th March)
Then the conference is also looking for:
In-Person Volunteers - https://accuconference.org/volunteers
Online Volunteers - https://docs.google.com/forms/d/e/1FAIpQLSdtl7iL4q6b266pIO_JrcKFcAqiss6T9o7azBB6E72Wu1MeVg/viewform?usp=sf_link
\---
# C++Now - https://cppnow.org/
Join us in-person for five days of C++ content, including C++ talks, group chats and networking at the Aspen Center for Physics which offers a unique and lively environment for thought, education, and collaboration.
Main Conference: Monday April 29th - Friday 3rd May
Location: In-Person at Aspen, Colorado
Registration: Is now open! More information can be found here https://cppnow.org/announcements/2024/02/2024-registration-is-open/ with ticket prices costing $1500
Latest News:
No news at the moment. However, am expecting an announcement of accepted talks in the next few days.
\---
# using std::cpp 2024 - https://eventos.uc3m.es/105614/detail/using-std-cpp-2024.html
using std::cpp 2024 is the largest Conference on C++ in Spain. It aims to serve as a forum to exchange experiences in the use of the C++ programming language, which pays special attention to last versions of the language, as well as upcoming features
Main Conference: Wednesday 24th - Friday 26th April
Location: In-Person at Madrid, Spain
Registration: Registration is now open with a minimum early registration cost of 25 € https://eventos.uc3m.es/105614/detail/using-std-cpp-2024.html
Latest News: The program was published here https://eventos.uc3m.es/105614/programme/using-std-cpp-2024.html
\---
# C++OnSea - https://cpponsea.uk/
C++ on Sea is an international C++ conference taking place by the sea, in the UK.
Workshops: Tuesday 2nd July
Main Conference: Wednesday 3rd - Friday 5th July
Location: In-Person at Folkestone, England
Registration: Is now open! https://cpponsea.uk/tickets/ with Early
Generate Code for C++ FlatBuffers database objects (new release 0.14)
https://github.com/objectbox/objectbox-generator/releases/tag/v0.14.0
https://redd.it/1b7597x
@r_cpp
RAII all the things?
https://biowpn.github.io/bioweapon/2024/03/05/raii-all-the-things.html
https://redd.it/1b75jgd
@r_cpp
What is one thing you love about programming, and one thing you hate about programming.
https://redd.it/1b74utf
@r_cpp
Un ejemplo utilizando STL de C++
https://emanuelpeg.blogspot.com/2024/03/un-ejemplo-utilizando-stl-de-c.html
https://redd.it/1b9kkic
@r_cpp
Which GUI lib should I choose?
Hello r/cpp,
I really obsessed about c++, I take part in every Olympiad I could ever join, I solve a majority of problems in the CodeForces & LeetCode, I was trying to build own pet proj on my github etc. However, as I am learning Swift lang too, I become highly curious about creating some graphics application on my computer(MacBook M1), unfortunately, while I was searching the right lib for this I have lost in the thousands of options. After a couple of time, I focused on 3 main(from my view) ones - SDL2, SFML, ImGui. After that I was trying to experience all the libraries, but I`ve got hundreds of errors(I don`t really know why) and at that time I was too exhausted, therefore I had a break. Now I recharged my batteries and ready for study.
Please, help me to choose which lib to choose. At the start all I wanted is visualise some c++ algorithms, like bobble sort and other, but if I like the way I coding, I would definitely start something more challenging.
Thanks for all reddit users!
https://redd.it/1b9ddej
@r_cpp
C++ Club 170: WG21 Feb '24 Mailing, C++ Successors, Reflection, Pattern Matching
https://youtu.be/vMIvCyW-Qnc
https://redd.it/1b98t9t
@r_cpp
Enabling Fine-Grained Incremental Builds by Making Compiler Stateful
https://conf.researchr.org/details/cgo-2024/cgo-2024-main-conference/27/Enabling-Fine-Grained-Incremental-Builds-by-Making-Compiler-Stateful
https://redd.it/1b90mbb
@r_cpp
poll Hypothetical syntax options for reflection splicing.
The current reflection paper for C++26 P2996 proposes [: ... :\] syntax for the reflection splicing. The paper also has section 4.2.2 Syntax discussion in which it is mentioned that $<expr> syntax could also be used, as characters $, @ and ` are added to the basic character set in C++26.
This got me thinking that what if the splicer syntax would use the coming grave accent ` as the delimiter, so simply `...`. This would not collide with any other C++ syntax and it would be little lighter than [: ... :\] which requires special rule e.g. for `arr[::global\]`.
I somewhat like `...` this because it reminds me of a bash syntax for command substitution. Below is comparisons of the hypothetical syntax options:
if (value == :e:) {
typename:e: foo = bar;
foo.data.:get_nth_field(^decltype(t.data), I):;
}
if (value == e) {
typenamee foo = bar;
foo.data.get_nth_field(^decltype(t.data), I);
}
if (value == $e) {
typename$e foo = bar;
foo.data.$getnthfield(^decltype(t.data), I);
}
So what do you think? Is `...` too subtle syntax?
edit. I should have known reddit, of course the formatting is different for the polling options from the rest of the post and it can not be edited...
View Poll
https://redd.it/1b8v3wz
@r_cpp
What happened to Ashampoo Boden cross-platform C++ framework?
Flutter/Qt/Delphi Firemonkey alternative in C++: https://github.com/AshampooSystems/boden
https://redd.it/1b8qp7t
@r_cpp
Imposter syndrome
So, idk why im posting this but i guess I need a form of clarity or a "happened to me too moment"? But anyway I graduated with a CS bachelors around the time covid happened, during covid i was applying for work and stumbled upon this top 500 company who needed a "product owner" at the time I didnt know what that meant but I applied and my boss told me that I would be solving problems and coming up with cool stuff so i accepted that position, ive worked there since now coming up with product ideas and general systems which make people's and the internal organizations lives easier mind you i havent written a single line of code since getting the bachelors.
So fast forward i see these FANG companies lay off alot of their staffs and in that there are people getting laid off among those people it's usually the product owners, project managers, analysts etc so i get worried and I started applying for development jobs and have been writing code to refresh my memory since June 2023. So fast forward till now I have a c++ interview, I did c++ in varsity and im above average with it, it's a junior position too. I feel like if i get accepted for a developing position, in a meeting my boss would go "hey you tell us about ____" and imma be found speechless, so im posting to ask is having imposter syndrome normal and how did you guys deal with it?
https://redd.it/1b8pgn3
@r_cpp
How do I make an expression non-movable? What's the opposite of std::move? - The Old New Thing
https://devblogs.microsoft.com/oldnewthing/20240306-00/?p=109481
https://redd.it/1b8nxca
@r_cpp
Equation implementation
Hi everyone, I have in my mind a project, but I didn't found any example.
I would like to implement a c++ code that emulate a TCAD simulation on a simple PN junction.
I recovered all the equations manually, but as you can know, the equation for drift and diffusion, are differential equation, these are recovered from Poisson equation.
I implemented a code in MATLAB in 1Dimension, it is just a matter of write the equation and plot. Now I would like to implement a code that solve the equation and plot the solution.
Obviously, PN junction is very easy to verify the results, but I didn't found any similar implementation.
Steps for 1D:
1) write the conditions
2) solve the Differenzial equation in 1Dimension
3) plot the results.
Steps for 2Dimension is pretty complex:
1) draw a boundary (rectangle)
2) create a mesh in the rectangle
3) give the boundary conditioning
4) start to solve the system for every point of the mesh.
Someone has an idea how to implement the solver for a differential equation? In this case, should be a discrete solver with one of the classic method, newton, crank-nicholson etc?
Any idea from where to start to create a small peace of code?
https://redd.it/1b8btps
@r_cpp
Why can't partial specializations be friends?
I'm working on a generic library, and I ran across this somewhat puzzling restriction - I was wondering if anyone could give insight on why this is, and if there's any workaround.
template <typename T, std::size_t N>
class Foo {
// Friend any Foo - This works!
template <typename T2, std::size_t N2>
friend class Foo;
// Friend one specific Foo - This works too!
friend class Foo<T, N + 1>;
// Friend some Foo's - This doesn't work
template <std::size_t N2>
friend class Foo<T, N2>;
// Clang error: partial specialization cannot be declared as a friend
// GCC error: specialization of 'template<class T, long unsigned int N> class
// Foo' must appear at namespace scope
// MSVC error C3772: 'Foo<T,N2>': invalid friend template declaration
};
Some alternatives I tried were doing the unspecialized template friend class declaration with constraints in the friend declaration - no dice, that's an error too if the constraints don't match the original template declaration.
Any thoughts on if this is fixable or avoidable, and why it's like this?
https://redd.it/1b7jkxd
@r_cpp
Bird available for £425 + VAT. More of an explanation about the different options are available here https://cpponsea.uk/news/early-bird-tickets-now-available-with-a-new-option.html and all registrations include access to next week's C++Online Main Conference (or if you register after next week, then it will be for C++Online 2025)
Latest News:
The Call for Speakers is still open but will close on 8th March. More information can be found at https://cpponsea.uk/callforspeakers/
Then C++OnSea have also announced Daniela Engert, Dave Abrahams & Klaus Iglberger as their keynote speakers https://cpponsea.uk/news/keynote-speakers-for-cpp-on-sea-2024.html
\---
# CppNorth - https://cppnorth.ca/
Building from the success of the Toronto user group, CppNorth will bring together local and visiting speakers for three days filled with opportunities to learn, network and discover what is new in the C++ community.
Dates: Sunday 21st - Wednesday 24th July
Location: In-Person at Toronto, Canada
Registration: CppNorth have opened their early bird ticket registration which will finish on Monday 15th April https://store.cppnorth.ca/products/cppnorth-2024
Latest News:
The call for speakers has now closed.
\---
# CppCon - https://cppcon.org
CppCon is the annual, week-long face-to-face gathering for the entire C++ community. Taking place this year in Aurora, Colorado, near the Denver airport, and including multiple diverse tracks, the conference will appeal to anyone from C++ novices to experts.
Workshops: Saturday 14th & Sunday 15th September, Saturday 21st & Sunday 22nd September
Main Conference: Monday 16th - Friday 20th September
Location: In-Person in Aurora, Colorado
Latest News:
The deadline to submit a class/workshop proposal for the CppCon Academy has now passed.
https://redd.it/1b79p7s
@r_cpp
Primeagen - Gemini WON'T SHOW C++ To Underage Kids (it's not safe)
primeagen - Gemini won't show c++ to underage kids (it's unsafe)
original article
Google is biased against our community ;)
https://redd.it/1b77ndf
@r_cpp
C++ Engineers career path ?
Hi,
I'm a C++ Software Engineer for few years now, about 4 and there are some thoughts that come to my mind lately.
What should I do next? I mean ok I know C++, some QT some networking but I'm feeling like I have no expertise area.
I can learn Python which is a language that I already know as a basic level.
​
Are you specialized in let's say embedded? Computer Vision?
​
What do you think? What are the following steps for a C++ Engineer?
​
https://redd.it/1b78v3r
@r_cpp
C++ Dark Corners
C++ is known to be highly complex language with a lot dark corners that will get you if you're not careful.
So what's the most disturbing things in the language?
And did it result in a hard to fix bug in your codebase?
https://redd.it/1b769zu
@r_cpp
Recommendation for security oriented conferences within EU
Hi guys,
Are there any recommendations for the security oriented conferences within EU for C++ / Backend Developers?
Thanks a lot for the feedback!
https://redd.it/1b7070l
@r_cpp
