C++ error

[Laurent Gatto <laurent.gatto@gmail.com>]

Dear all,

I have this very simple code chunk

$ cat main.cpp
#include <iostream>

int main(void) {
    std::cout << __cplusplus;

    return 0;
}

That I can compile in a minimal shell

$ guix shell --container gcc-toolchain
[env]$ g++ main.cpp && ./a.out
201703

However, on my main system, I get

$ g++ main.cpp
In file included from /home/lgatto/.guix-profile/include/c++/bits/move.h:57,
                 from
/home/lgatto/.guix-profile/include/c++/bits/exception_ptr.h:43,
                 from /home/lgatto/.guix-profile/include/c++/exception:153,
                 from /home/lgatto/.guix-profile/include/c++/ios:39,
                 from /home/lgatto/.guix-profile/include/c++/ostream:38,
                 from /home/lgatto/.guix-profile/include/c++/iostream:39,
                 from main.cpp:1:
/home/lgatto/.guix-profile/include/c++/type_traits:732:26: error:
expected identifier before ‘(’ token
  732 |     _GLIBCXX20_DEPRECATED("use is_standard_layout &&
is_trivial instead")
      |                          ^
/home/lgatto/.guix-profile/include/c++/type_traits:732:27: error:
expected unqualified-id before string constant
  732 |     _GLIBCXX20_DEPRECATED("use is_standard_layout &&
is_trivial instead")
      |                           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/lgatto/.guix-profile/include/c++/type_traits:732:27: error:
expected ‘)’ before string constant
  732 |     _GLIBCXX20_DEPRECATED("use is_standard_layout &&
is_trivial instead")
      |                          ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      |                           )
/home/lgatto/.guix-profile/include/c++/type_traits:3154:25: error:
expected unqualified-id before string constant
 3154 |   _GLIBCXX20_DEPRECATED("use is_standard_layout_v &&
is_trivial_v instead")
      |
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/lgatto/.guix-profile/include/c++/type_traits:3154:25: error:
expected ‘)’ before string constant
 3154 |   _GLIBCXX20_DEPRECATED("use is_standard_layout_v &&
is_trivial_v instead")
      |
~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      |                         )


Other issues lead me to suspect that I lost support for C++17 and beyond.

Any idea what/how I messed up and how to fix this?

Thanks in advance.

Laurent