Redefinition on the same line (Yes I ve inlcude guards) | Together C & C++ | Page 1

chilly nimbus Sep 4, 2022, 1:44 PM

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Hi ! You all.
I am reimplementing the STL vector in C++98 as an exercise and so far so good but I stumbled upon a compilation error I can't make sense of.
I have been unable to produce a snippet of what's wrong because it's too big. Instead I have made a replit : https://replit.com/join/bbfribyaff-cassepipe
You can also see what's wrong on your machine with
git clone https://github.com/cassepipe/kontainerz and just running make. What it does is build to executables, one with std::vector and one with my own ft::vector and compare their ouptut.
Before you ask, yes I double checked all my include guards

safe tapirBOT Sep 4, 2022, 1:44 PM

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novel wolf Sep 4, 2022, 1:45 PM

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Can you send a https://godbolt.org link instead

Compiler Explorer

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replit requires an account

chilly nimbus Sep 4, 2022, 1:46 PM

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@novel wolf I can't upload various files to godbolt right ?

novel wolf Sep 4, 2022, 1:46 PM

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chilly nimbus Sep 4, 2022, 1:46 PM

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Since it's a compilation issue it does not make sense to combine everythin in one source file

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Oooooooh

novel wolf Sep 4, 2022, 1:47 PM

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alternatively to tree mode, it actually very much makes sense to combine everything into one file 😛

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#include is a dumb copy-paste

chilly nimbus Sep 4, 2022, 1:50 PM

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I tried many times, I have an awk script for that and then I have to remove all my inlcudes but it failed somehow I cna't remember why

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Do you happen to how to give godbolt a makefile ?

novel wolf Sep 4, 2022, 1:51 PM

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tree mode takes a *cmakefile

chilly nimbus Sep 4, 2022, 1:51 PM

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Oh it's jsut cmake apparently

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Here the link without all the cruft https://godbolt.org/z/KM7Y8G1WM

Compiler Explorer - C++ (x86-64 gcc 12.2)

Compiler Explorer is an interactive online compiler which shows the assembly output of compiled C++, Rust, Go (and many more) code.

novel wolf Sep 4, 2022, 1:55 PM

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https://godbolt.org/z/x8b6zW7Eq

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here

chilly nimbus Sep 4, 2022, 1:55 PM

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Ha, damn i have to learn Cmake

novel wolf Sep 4, 2022, 1:56 PM

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I don't know cmake, I just copy paste from google yamikek

chilly nimbus Sep 4, 2022, 1:57 PM

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Lol, ok

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I have put that in the roor of my project : https://dpaste.com/BZLNVSKMC

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but calling cmake or cmake --build . does not work

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I mean could someone just git clone that on his desktop, run make and see what he understands

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Damn it's so hot here

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It's turning into a nightmare

novel wolf Sep 4, 2022, 2:06 PM

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If your test code is reduced to

void test_vector()
{
    test_vector_begin();
}

void test_vector_assign()
{
    {
        vector<int> my_vec;
        for (vector<int>::size_type i = 0; i < 42; ++i)
            my_vec.push_back(i + 1);
        std::cout << "my_vec" << std::endl;
        std::cout << "size : " << my_vec.size() << std::endl;
        for (vector<int>::iterator it = my_vec.begin(); it != my_vec.end(); it++)
        {
            std::cout << *it;
            if (it + 1 != my_vec.end())
                std::cout << " ";
        }
    }
}

void test_vector_begin()
{
    {
        const vector< int > my_const_vec(10, 42);
        vector< int >::const_iterator constIt = my_const_vec.begin();
    }
}

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the code compiles if you comment out the for (vector<int>::iterator it = my_vec.begin(); it != my_vec.end(); it++) part

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something about things getting confused with the const iterator

chilly nimbus Sep 4, 2022, 2:07 PM

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I know but I don't understand the problem

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And I am not a total noob, I kinda know what I am doing

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I am saying so that don't think I don't understand the basics of compilation, templating etc.

novel wolf Sep 4, 2022, 2:12 PM

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Here's a minimal reproducible example of the problem https://godbolt.org/z/G3E4qro4x

Compiler Explorer - C++ (x86-64 gcc 12.2)

template<typename T>
struct S {
void foo() {}
template<typename L, typename R>
friend void operator+(const S<L>& a, const S<R>& b) {

};

void bar() {
S<int> s;
S<const int> x;
s.foo();
x.foo();
s + s;
x + x;
}

chilly nimbus Sep 4, 2022, 2:13 PM

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Oh thank you so much

novel wolf Sep 4, 2022, 2:15 PM

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the problem and solution is: ||Both S instantiations create that friend template definition so instead only make the friend declaration in the class https://godbolt.org/z/ajobo4sh1||

chilly nimbus Sep 4, 2022, 2:17 PM

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Haa this is tempting

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Thank you so much. I'll give myself another ten minutes before I look

novel wolf Sep 4, 2022, 2:19 PM

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that is a good idea 😄

chilly nimbus Sep 4, 2022, 2:21 PM

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Damn I'd have never thought of that, I thought the compiler was smart enough to deal with that

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The template engine is midway through a dumb C preprocessor and generic type deduction, what a weird beast

novel wolf Sep 4, 2022, 2:29 PM

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this is where C++ gets extremely intricate and complicated

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unfortunately 😦

chilly nimbus Sep 4, 2022, 2:44 PM

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It did solve my problem but now I have a linker problem

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The linker complains about not being able to find the operator- definition on the two iterators

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I am trying to condense it into somthing manageable like you didi

safe tapirBOT Sep 5, 2022, 1:52 AM

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@chilly nimbus

This question thread is being automatically closed. If your question is not answered feel free to bump the post or re-ask. Take a look at !howto ask for tips on improving your question.

novel wolf Sep 5, 2022, 1:52 AM

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oh shit

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I fucked up

#Redefinition on the same line (Yes I ve inlcude guards)