/tech/ - Technology★

>>811729 (OP)

You used it

>>doesnt warn about unused s

Looks like it's the same for clang. Pretty strange, since

#include <stdio.h>

int main(void) {
    char *s;
    int n = 5 / 2;
    printf("%d\n", n);
    return 0;
}

gives a unused variable ‘s’ warning. Must be because C++ is for faggots.

>>doesnt warn about loss of information when truncating to int

Truncating what to int, retard? It's an integer division.

>>811729 (OP)

>doesnt warn about loss of information when truncating to int

What loss? Integer division is truncating the remainder by design, if you do integer division it's assumed you want the remainder to be truncated.

>>811729 (OP)

gcc is for commie faggots

use clang

>>811731

i'll bet you it compiles it out anyway.

>>811764

this

>>811766

meme license that doesn't even require the source to be made available

https://en.wikipedia.org/wiki/Category:Software_using_the_NCSA_license

>>811767

meme license is better than meme license+messy code

>>811729 (OP)

Did you use -Wall -Wextra?

>>811766

>use clang

In the words of Scott Meyers, is there a Windows package for it, faggot? An official standalone distro that doesn't require either Visual Studio or GCC to be installed? One that comes bundled with stdc++ out of the box?

>>811729 (OP)

It can warn you, you have to enable verbose warnings when compiling.

int round down is a great thing, considering you can always get the remainder with a %.

>>811729 (OP)

your shitty bait doesnt even compile

https://godbolt.org/g/AAS6CA

>>811771

-Wall -Wextra -pedantic -O2

>>811778

You can't catch bait with bait.

>>811807

are you saying that im baiting? because i most assuredly am not. i just popped what op posted into godbolt and it doesnt compile.

>>811729 (OP)

std::string isn't unused. It has a non-trivial constructor that can throw. Welcome to C++.

>>811808

Better to claim you were pretending to be retarded than just being retarded.

#include <string>
#include <iostream>
int main() {
    std::string s;
    int n = 5 / 2;
    std::cout << n << "\n";
}

>>811810

>not knowing c++ makes you a retard

ok fag

>>811811

>claiming something doesn't work despite being clueless of if it's communicating anything to other programmers

Yeah, you're retarded. Just stay out of discussions you have no clue about.

>>811811

>acts retarded

>claims not to be a retard

ok

>>811813

>>811812

>samefagging

please tell me why op didnt just post working code???

const bool OP = faggot

>>811817

nice photoshoop fag

>>811820 (You)

>>811815 (You)

Here are your (You)s

Why are the shittiest threads and comments when Europe is awake?

>>811822

thx

>>811823

because i, steve klabnik am a europoor

>>doesnt warn about loss of information when truncating to int

I don't see any truncation to int here. You're taking two integers and performing integer division on them, giving you an integer. Where's the problem?

>>811822

>>811820

>>811818

>>811817

Christ, this is why /tech/ needs ID's.

>>811729 (OP)

big if true

Want something even more retarded?

#include <stdio.h>

int

main(void)

{

	char s[2];

	fgets(s, 1, stdin);

	return 0;

}

No warning with -Wall -Wextra.

Warning with -O1 without -Wall and -Wextra.

int main() {
   char s[1];
   gets(s);
   return *s;
}

>>812857

>reddit spacing

>even in the code

wow im hyper triggered

>>812857

I don't get it, what's wrong with it, reddit friend?

>>812874

I think the whole "reddit spacing" meme is retarded, but if you feel as annoyed as I do when I see code like that, I understand. I'm sorry I used to hate you ">reddit-spacing" autists, I understand now. I'll continue separating paragraphs with blank lines though.. just squint your eyes and it'll look all cramped up again.

>>812904

https://developer.mozilla.org/en-US/docs/Web/CSS/line-height

>>812874

>>812880

Actually, that's 8chan fucking up my copy-pasted code. Now, do you have an argument, my sweet sweet 9GAG memers?

>>812991

Kill yourself.

>>812908

I'm not going to change how I type my posts just so your custom style sheet looks better.

>>813076

I'll take that as a no. Thank you, 9GAG.

>>811809

Interesting can you explain?

>OP

<I'm very smart lads

>>813676

classes with constructors can have side-effects, so you can't just elide these "unused" variables as they actually did something that might change program execution, unless the compiler can detect the constructor does nothing. Who knows what std::string's constructor is actually doing as it changes so often, but the compiler is apparently confident that it has some possible side-effect so has left it in.

>>811810

>using iostream

just use stdio.h in C++. avoid the cancer.

>>813702

(((the compiler)))

a great unknown entity

>>813715

whats so bad about iostream? speed seems to be the same as printexploitf

>>813719

>speed seems to be the same as printexploitf

In what universe?

#ifdef SEPPLES
#include <iostream>
#else
#include <stdio.h>
#endif

int main(int argc, char *argv[]) {
        volatile int a = 1;
        volatile char b = 'b';
        for(int i = 0; i < 1000000; ++i) {
#ifdef SEPPLES
                std::cout << "a number: " << i << ", a letter: " << b << ", a nothing:" << std::endl;
#else
                printf("a number: %d, a letter: %c, a nothing:\n", a, b);
#endif
        }
}
[code]

To /dev/null, C:
[code]
real    0m0.056s
user    0m0.052s
sys     0m0.000s

SheePrusPrus:

real    0m0.294s
user    0m0.140s
sys     0m0.152s

Bonus: Try internationalizing the C++ version. You fucking can't. It's also much larger and also is shit. strings and streams are the worst parts of C++ and should be avoided as much as possible.

>>811823

Because that also means eastern europe is also awake

>>813727

Actually, IOStreams don't have to be slow! It is a matter of implementing them in a reasonable way to make them fast, though. Most standard C++ library don't seem to pay too much attention to implement IOStreams. A long time ago when my CXXRT was still maintained it was about as fast as stdio - when used correctly!

Note that there are few performance traps for users laid out with IOStreams, however. The following guidelines apply to all IOStream implementations but especially to those which are tailored to be fast:

1. When using std::cin, std::cout, etc. you need to call std::sync_with_stdio(false)! Without this call, any use of the standard stream objects is required to synchronize with C's standard streams. Of course, when using std::sync_with_stdio(false) it is assumed that you don't mix std::cin with stdin, std::cout with stdout, etc.

2. Do not use std::endl as it mandates many unnecessary flushes of any buffer. Likewise, don't set std::ios_base::unitbuf or use std::flush unnecessarily.

3. When creating your own stream buffers (OK, few users do), make sure they do use an internal buffer! Processing individual characters jumps through multiple conditions and a virtual function which makes it hideously slow.

>>813727

>0.294s

>0.140s

fuck that's slower than python

$ cat shit.py
def main():
	a=1
	b='a'
	print "a number: "+str(1)+", a letter: "+b+", a nothing:"

if __name__=="__main__":
	main()
$ time python2.7 shit.py
a number: 1, a letter: a, a nothing:

real    0m0.019s
user   0m0.012s
sys	  0m0.004s

>>813742

>Actually, IOStreams don't have to be slow! It is a matter of implementing them in a reasonable way to make them fast, though.

No, they have to be slow without breaking the standard. The issue is baked into the design. Check out xsputn, for example. All these low-level streambuf functions were defined virtual as people had a hard-on for OOP at the time and templates weren't a fully fleshed out concept both in terms of code and how people thought of their use. The result is code any compliant C++ compiler can never optimize away and a lot of pointless calls.

We need a compete redesign of the strings/streams layer in C++. And also for exception::what() to return a string so you don't have to pay the cost of generating a string people will likely never request or hacking it with a mutable.

>>813743

The C++ version prints 1,000,000 times. However, the python version modified to print that many times is still actually almost as fast as C++.

def main():
    for i in xrange(1000000):
        a=1
        b='a'
        print "a number: "+str(1)+", a letter: "+b+", a nothing:"

if __name__=="__main__":
        main()

real    0m0.314s
user    0m0.312s
sys     0m0.000s

This is why people say to avoid this shit in C++.

>>811729 (OP)

it doesn't faggot, because you didn't give compilation flags, fuck off piece of shit

>>813996

Wow omg shes so cute ^^

Using clang from now on!

>>811729 (OP)

>what is -Wall -Wextra -Werror -pedantic

>what is integer division

Delete this shit thread.

>>813764

>>814011

see >>811806

i understand you want to show off your retardation but this is too much

>>812809

kek

sage for shit thread anyway

>>813977

OP didn't mention that, you retard, apparently there needs to be several posts about something to get people actually realize the thing

<the state of /tech/ in late 2017

>>813764

How could anyone get mad like this over such a thing.

>>813727

>making a variable that's already used volatile for benchmarking

>>811729 (OP)

>>doesnt warn about loss of information when truncating to int

> thinks that all arithmetic is done in floating point

> pajeet detected

>>826250

Making it volatile prevents the compiler potentially optimizing away a lot of the code. Two files could have been used instead where one calls the other and passes the values to similarly prevent cheating.

>>811816

>When you don't understand booleans

>>828552

Surely gender is an enum.

>>811729 (OP)

>>811764

What I'm personally pissed about (C++, not the compiler) is it doesn't warn about integer overflow or underflow.

t. large numbers fag.

 
#include<iostream>
using namespace std;
int main(){
int a1 = 319746;
int a2 = 619692056;
int fuckMe = a1*a2/a2;
cout<<a1<<" "<<a2<<" "<<fuckMe<<"\n";}

>>828563

The compiler isn't going to wipe your ass for you when it comes to mathematical bounds and precision, you need to know how to use numbers. You're in for a shock when you start using floats.

>>828563

Use GMP

https://gmplib.org