Hello,

A typical "hello world" C++ f= ails in an environment with both
`gcc-toolchain' and `clang-toolchain', = apperently due to the setup of
the `CPLUS_INCLUDE_PATH' environment vari= able (used because of the
`#include <iostream>' instruction), when= compiling with `clang++'.

I do not know if this is a bug or the exp= ected behaviour. Obviously one

is not likely to explicitly load = an environment with both `gcc-toolchain'

and `clang-toolchain' b= ut migth do so implictly (and possibly not being
aware of it) for instan= ce having `gcc-toolchain' globally installed and
at some point loading `= clang-toolchain' in an environment.

Note that it is not critical at = all in practice in my case, and I do
not know whether it it is desirable= to fix it in some way, or, maybe
mention the incompatibility somewhere<= br>(<https://guix.gnu.org/manual/en/html_node/Development.html> ?) if= not
already done so =E2=80=93 in which case I am sorry for the noise.
Please find below:
1. a simplified C++ "hello world" hello.cpp pro= gram
2. an expected g++ behaviour in a `gcc-toolchain' environment
3.= an expected clang++ behaviour in a `clang-toolchain' environment
4. an = environment with both `gcc-toolchain' & `clang-toolchain'
- 4.1. wit= h an expected behaviour using `g++'
- 4.2. with an (expected or not?) er= ror using `clang++'
- 4.3. a (non desirable) fix of the `CPLUS_INCLUDE_P= ATH' (removing
`/gnu/store/=E2=80=A6/include/c++')
5. the empl= oyed channels if it may help

Thanks much for the continous developme= nt and support, and once

again sorry for the possible noise if th= is is a known expected

behaviour.

With best regards,
Emmanuel

1 simplified (no newline) C++ "hello world" hello.cpp= program
=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90= =E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2= =95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95= =90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90= =E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2= =95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95= =90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90= =E2=95=90=E2=95=90=E2=95=90=E2=95=90

=E2=94=8C=E2=94=80=E2=94= =80=E2=94=80=E2=94=80
=E2=94=82 #include <iostream>
&nbs= p; =E2=94=82
=E2=94=82 int main() {
=E2=94=82 &nb= sp;   std::cout << "Hello World!";
=E2=94=82 = ;    return 0;
=E2=94=82 }
=E2=94=94=E2= =94=80=E2=94=80=E2=94=80=E2=94=80

2 `gcc-toolchain' environment<= br>=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90= =E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2= =95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95= =90=E2=95=90=E2=95=90=E2=95=90=E2=95=90

=E2=94=8C=E2=94=80=E2= =94=80=E2=94=80=E2=94=80
=E2=94=82 guix environment -C --ad-hoc g= cc-toolchain coreutils grep
=E2=94=82 env | grep CPLUS_INCLUDE_PA= TH
=E2=94=82 g++ hello.cpp
=E2=94=82 ./a.out
= =E2=94=94=E2=94=80=E2=94=80=E2=94=80=E2=94=80

=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81
   CPLUS_INCLUDE_PATH=3D/gnu/store/gsylxn8q06w6y7622nw159f= 3q1vvcx2i-profile/include/c++:/gnu/store/gsylxn8q06w6y7622nw159f3q1vvcx2i-p= rofile/include
&n= bsp; Hello           = ;            &n= bsp;            = ;            &n= bsp;            = ;            &n= bsp;            = ;            &n= bsp;            = ;            &n= bsp;            = ;   World!
=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81

3 `clang-too= lchain' environment
=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95= =90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90= =E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2= =95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95= =90

=E2=94=8C=E2=94=80=E2=94=80=E2=94=80=E2=94=80
= =E2=94=82 guix environment -C --ad-hoc clang-toolchain coreutils grep
&n= bsp; =E2=94=82 env | grep CPLUS_INCLUDE_PATH
=E2=94=82 clang++ he= llo.cpp
=E2=94=82 ./a.out
=E2=94=94=E2=94=80=E2=94=80= =E2=94=80=E2=94=80

=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=
   CPLUS_INCLUDE_PATH=3D/gnu/store/8qlafmilvc0g1yv8lmilpjmps3= p4nrmq-profile/include
=    Hello         &nb= sp;            =             &nb= sp;            =             &nb= sp;            =    World!
=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=

4 environment with both `gcc-toolchain' & `clang-toolchain'=
=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95= =90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90= =E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2= =95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95= =90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90= =E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2= =95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95= =90=E2=95=90

4.1 compilation with `g++'
=E2=94=80=E2=94=80=E2=94= =80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80= =E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2= =94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80

= `g++' in an environment with both gcc and clang toolchains is fine:
&nbs= p; =E2=94=8C=E2=94=80=E2=94=80=E2=94=80=E2=94=80
=E2=94=82 guix e= nvironment -C --ad-hoc gcc-toolchain clang-toolchain coreutils grep
&nbs= p; =E2=94=82 env | grep CPLUS_INCLUDE_PATH
=E2=94=82 g++ hello.cp= p
=E2=94=82 ./a.out
=E2=94=94=E2=94=80=E2=94=80=E2=94= =80=E2=94=80

=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81
   CPLUS_INCLUDE= _PATH=3D/gnu/store/3ka3a9wgx5sk6ac84nldx7ldpxppn29z-profile/include/c++:/gn= u/store/3ka3a9wgx5sk6ac84nldx7ldpxppn29z-profile/include   &= nbsp;
   Hello    = ;            &n= bsp;            = ;            &n= bsp;            = ;            &n= bsp;            = ;            &n= bsp;            = ;            &n= bsp;            = ;          World!
= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2= =94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94= =81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81=E2=94=81= =E2=94=81=E2=94=81

4.2 compilation with `clang++' (FAIL)
=E2= =94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94= =80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80= =E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2= =94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94= =80=E2=94=80=E2=94=80=E2=94=80

But `clang++' in the same envi= ronment (with both gcc and clang
toolchains) breaks, raising the = following error:
=E2=94=8C=E2=94=80=E2=94=80=E2=94=80=E2=94=80 =E2=94=82 guix environment -C --ad-hoc gcc-toolchain clang-toolchai= n coreutils grep
=E2=94=82 clang++ hello.cpp
=E2=94=94= =E2=94=80=E2=94=80=E2=94=80=E2=94=80

Error obtained during th= e `clang++ hello.cpp' step:
=E2=94=8C=E2=94=80=E2=94=80=E2=94=80= =E2=94=80
=E2=94=82 In file included from hello.cpp:1:
= =E2=94=82 In file included from /gnu/store/3ka3a9wgx5sk6ac84nldx7ldpxppn29z= -profile/include/c++/iostream:39:
=E2=94=82 In file included from= /gnu/store/3ka3a9wgx5sk6ac84nldx7ldpxppn29z-profile/include/c++/ostream:38= :
=E2=94=82 In file included from /gnu/store/3ka3a9wgx5sk6ac84nld= x7ldpxppn29z-profile/include/c++/ios:39:
=E2=94=82 /gnu/store/3ka= 3a9wgx5sk6ac84nldx7ldpxppn29z-profile/include/c++/exception:105:3: error: u= nknown type name '_GLIBCXX17_DEPRECATED'
=E2=94=82   _G= LIBCXX17_DEPRECATED
=E2=94=82   ^
=E2=94=82 I= n file included from hello.cpp:1:
=E2=94=82 In file included from= /gnu/store/3ka3a9wgx5sk6ac84nldx7ldpxppn29z-profile/include/c++/iostream:3= 9:
=E2=94=82 In file included from /gnu/store/3ka3a9wgx5sk6ac84nl= dx7ldpxppn29z-profile/include/c++/ostream:38:
=E2=94=82 In file i= ncluded from /gnu/store/3ka3a9wgx5sk6ac84nldx7ldpxppn29z-profile/include/c+= +/ios:39:
=E2=94=82 In file included from /gnu/store/3ka3a9wgx5sk= 6ac84nldx7ldpxppn29z-profile/include/c++/exception:147:
=E2=94=82= In file included from /gnu/store/3ka3a9wgx5sk6ac84nldx7ldpxppn29z-profile/= include/c++/bits/exception_ptr.h:40:
=E2=94=82 /gnu/store/3ka3a9w= gx5sk6ac84nldx7ldpxppn29z-profile/include/c++/new:126:1: error: unknown typ= e name '_GLIBCXX_NODISCARD'
=E2=94=82 _GLIBCXX_NODISCARD void* op= erator new(std::size_t) _GLIBCXX_THROW (std::bad_alloc)
=E2=94=82= ^
=E2=94=82 /gnu/store/3ka3a9wgx5sk6ac84nldx7ldpxppn29z-profile/= include/c++/new:128:1: error: unknown type name '_GLIBCXX_NODISCARD'
&nb= sp; =E2=94=82 _GLIBCXX_NODISCARD void* operator new[](std::size_t) _GLIBCXX= _THROW (std::bad_alloc)
=E2=94=82 ^
=E2=94=82 /gnu/stor= e/3ka3a9wgx5sk6ac84nldx7ldpxppn29z-profile/include/c++/new:140:1: error: un= known type name '_GLIBCXX_NODISCARD'
=E2=94=82 _GLIBCXX_NODISCARD= void* operator new(std::size_t, const std::nothrow_t&) _GLIBCXX_USE_NO= EXCEPT
=E2=94=82 ^
=E2=94=82 /gnu/store/3ka3a9wgx5sk6ac= 84nldx7ldpxppn29z-profile/include/c++/new:142:1: error: unknown type name '= _GLIBCXX_NODISCARD'
=E2=94=82 _GLIBCXX_NODISCARD void* operator n= ew[](std::size_t, const std::nothrow_t&) _GLIBCXX_USE_NOEXCEPT
= ; =E2=94=82 ^
=E2=94=82 /gnu/store/3ka3a9wgx5sk6ac84nldx7ldpxppn2= 9z-profile/include/c++/new:174:1: error: unknown type name '_GLIBCXX_NODISC= ARD'
=E2=94=82 _GLIBCXX_NODISCARD inline void* operator new(std::= size_t, void* __p) _GLIBCXX_USE_NOEXCEPT
=E2=94=82 ^
= =E2=94=82 /gnu/store/3ka3a9wgx5sk6ac84nldx7ldpxppn29z-profile/include/c++/n= ew:175:10: error: cannot initialize return object of type 'int *' with an l= value of type 'void *'
=E2=94=82 { return __p; }
=E2=94= =82          ^~~
=E2= =94=82 /gnu/store/3ka3a9wgx5sk6ac84nldx7ldpxppn29z-profile/include/c++/new:= 176:1: error: unknown type name '_GLIBCXX_NODISCARD'
=E2=94=82 _G= LIBCXX_NODISCARD inline void* operator new[](std::size_t, void* __p) _GLIBC= XX_USE_NOEXCEPT
=E2=94=82 ^
=E2=94=82 /gnu/store/3ka3a9= wgx5sk6ac84nldx7ldpxppn29z-profile/include/c++/new:177:10: error: cannot in= itialize return object of type 'int *' with an lvalue of type 'void *'
&= nbsp; =E2=94=82 { return __p; }
=E2=94=82    =       ^~~
=E2=94=82 In file included fro= m hello.cpp:1:
=E2=94=82 In file included from /gnu/store/3ka3a9w= gx5sk6ac84nldx7ldpxppn29z-profile/include/c++/iostream:39:
=E2=94= =82 In file included from /gnu/store/3ka3a9wgx5sk6ac84nldx7ldpxppn29z-profi= le/include/c++/ostream:38:
=E2=94=82 In file included from /gnu/s= tore/3ka3a9wgx5sk6ac84nldx7ldpxppn29z-profile/include/c++/ios:39:
= =E2=94=82 In file included from /gnu/store/3ka3a9wgx5sk6ac84nldx7ldpxppn29= z-profile/include/c++/exception:148:
=E2=94=82 In file included f= rom /gnu/store/3ka3a9wgx5sk6ac84nldx7ldpxppn29z-profile/include/c++/bits/ne= sted_exception.h:40:
=E2=94=82 In file included from /gnu/store/3= ka3a9wgx5sk6ac84nldx7ldpxppn29z-profile/include/c++/bits/move.h:57:
&nbs= p; =E2=94=82 /gnu/store/3ka3a9wgx5sk6ac84nldx7ldpxppn29z-profile/include/c+= +/type_traits:696:27: error: expected unqualified-id
=E2=94=82&nb= sp;    _GLIBCXX20_DEPRECATED("use is_standard_layout &&a= mp; is_trivial instead")
=E2=94=82     &= nbsp;           &nbs= p;         ^
=E2=94=82 /g= nu/store/3ka3a9wgx5sk6ac84nldx7ldpxppn29z-profile/include/c++/type_traits:6= 96:27: error: expected ')'
=E2=94=82 /gnu/store/3ka3a9wgx5sk6ac84= nldx7ldpxppn29z-profile/include/c++/type_traits:696:26: note: to match this= '('
=E2=94=82     _GLIBCXX20_DEPRECATED("use= is_standard_layout && is_trivial instead")
=E2=94=82&nbs= p;            &= nbsp;            ^ =E2=94=82 /gnu/store/3ka3a9wgx5sk6ac84nldx7ldpxppn29z-profile/incl= ude/c++/type_traits:2648:5: error: unknown type name '_GLIBCXX20_CONSTEXPR'=
=E2=94=82     _GLIBCXX20_CONSTEXPR
= =E2=94=82     ^
=E2=94=82 /gnu/store/3ka3a9w= gx5sk6ac84nldx7ldpxppn29z-profile/include/c++/type_traits:2650:5: error: no= variable template matches partial specialization
=E2=94=82 =     _Require<__not_<__is_tuple_like<_Tp>>, =E2=94=82     ^
=E2=94=82 /gnu/store/= 3ka3a9wgx5sk6ac84nldx7ldpxppn29z-profile/include/c++/type_traits:2652:31: e= rror: expected ';' at end of declaration
=E2=94=82  &nb= sp;           is_move_ass= ignable<_Tp>>
=E2=94=82     &nb= sp;            =             &nb= sp;       ^
=E2=94=82 /gnu/store/3k= a3a9wgx5sk6ac84nldx7ldpxppn29z-profile/include/c++/type_traits:2653:10: err= or: unknown type name '_Tp'
=E2=94=82     swa= p(_Tp&, _Tp&)
=E2=94=82     &nbs= p;    ^
=E2=94=82 /gnu/store/3ka3a9wgx5sk6ac84nldx= 7ldpxppn29z-profile/include/c++/type_traits:2653:16: error: unknown type na= me '_Tp'
=E2=94=82     swap(_Tp&, _Tp&= ;)
=E2=94=82         = ;       ^
=E2=94=82 /gnu/store/3ka3= a9wgx5sk6ac84nldx7ldpxppn29z-profile/include/c++/type_traits:2654:51: error= : use of undeclared identifier '_Tp'
=E2=94=82   &= nbsp; noexcept(__and_<is_nothrow_move_constructible<_Tp>,
= ; =E2=94=82          &nbs= p;            &= nbsp;           &nbs= p;            &= nbsp; ^
=E2=94=82 /gnu/store/3ka3a9wgx5sk6ac84nldx7ldpxppn2= 9z-profile/include/c++/type_traits:2654:55: error: expected a type
= ; =E2=94=82     noexcept(__and_<is_nothrow_move_cons= tructible<_Tp>,
=E2=94=82     &nbs= p;            &= nbsp;           &nbs= p;            &= nbsp;           ^
&nbs= p; =E2=94=82 /gnu/store/3ka3a9wgx5sk6ac84nldx7ldpxppn29z-profile/include/c+= +/type_traits:2653:5: error: C++ requires a type specifier for all declarat= ions
=E2=94=82     swap(_Tp&, _Tp&) =E2=94=82     ^
=E2=94=82 fatal erro= r: too many errors emitted, stopping now [-ferror-limit=3D]
=E2= =94=82 20 errors generated.
=E2=94=94=E2=94=80=E2=94=80=E2=94=80= =E2=94=80

4.3 (non desirable) fix of the `CPLUS_INCLUDE_PATH' (r= emoving `/gnu/store/.../include/c++')
=E2=94=80=E2=94=80=E2=94=80=E2=94= =80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80= =E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2= =94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94= =80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80= =E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2= =94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94= =80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80= =E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2= =94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94= =80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80=E2=94=80= =E2=94=80=E2=94=80=E2=94=80=E2=94=80

For information, it is p= ossible (but obviously in general not
desirable) to fix the `CPLU= S_INCLUDE_PATH' variable (removing
`/gnu/store/.../include/c++'),= which leads to a correct compilation
(and execution).

&nb= sp; =E2=94=8C=E2=94=80=E2=94=80=E2=94=80=E2=94=80
=E2=94=82 guix = environment -C --ad-hoc gcc-toolchain clang-toolchain coreutils grep
&nb= sp; =E2=94=82 export CPLUS_INCLUDE_PATH=3D/gnu/store/3ka3a9wgx5sk6ac84nldx7= ldpxppn29z-profile/include
=E2=94=82 clang++ hello.cpp
= =E2=94=82 ./a.out
=E2=94=94=E2=94=80=E2=94=80=E2=94=80=E2=94=80
=E2=94=8C=E2=94=80=E2=94=80=E2=94=80=E2=94=80
=E2=94= =82 Hello World!
=E2=94=94=E2=94=80=E2=94=80=E2=94=80=E2=94=80

5 channels
=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95= =90=E2=95=90=E2=95=90=E2=95=90=E2=95=90

=E2=94=8C=E2=94=80=E2= =94=80=E2=94=80=E2=94=80
=E2=94=82 guix describe --format=3Dchann= els
=E2=94=94=E2=94=80=E2=94=80=E2=94=80=E2=94=80

= =E2=94=8C=E2=94=80=E2=94=80=E2=94=80=E2=94=80
=E2=94=82 (list (ch= annel
=E2=94=82         (= name 'guix-hpc)
=E2=94=82      &nbs= p; (url "https://gitlab.inria.fr/guix-hpc/guix-hpc.git")
= =E2=94=82         (commit
= =E2=94=82           "fa8= 7605fe93fb85b02dad9db246299bcf223f2e0"))
=E2=94=82  &nb= sp;    (channel
=E2=94=82    &= nbsp;    (name 'guix-hpc-non-free)
=E2=94=82 =         (url "https://gitlab.inria.fr/gu= ix-hpc/guix-hpc-non-free.git")
=E2=94=82    &= nbsp;    (commit
=E2=94=82    =        "43d8cb72144a183aa7a93499f9c59ec0f8424= 4b0"))
=E2=94=82       (channel
= =E2=94=82         (name 'gui= x)
=E2=94=82         (url= "https://git.savannah.gnu.org/git/guix.git")
=E2=94=82 &nbs= p;       (commit
=E2=94=82 &nb= sp;         "c6872990b51971922f3064= cba54ab752fcdc1559")
=E2=94=82      = ;   (introduction
=E2=94=82    &nbs= p;      (make-channel-introduction
=E2= =94=82           &nb= sp; "9edb3f66fd807b096b48283debdcddccfea34bad"
=E2=94=82 &nb= sp;           (openpgp-fi= ngerprint
=E2=94=82       &nbs= p;       "BBB0 2DDF 2CEA F6A8 0D1D E643= A2A0 6DF2 A33A 54FA")))))
=E2=94=94=E2=94=80=E2=94=80=E2=94=80= =E2=94=80