Re: C++ error

[Laurent Gatto]

Hi Fredrik,

Thank you for taking the time looking into this.

My issue doesn't seem to be related to an old gcc version.

```
$ g++ --version
g++ (GCC) 14.2.0
Copyright (C) 2024 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
```

My location is different though

```
$ which g++
/home/lgatto/.guix-profile/bin/g++
```
Checking the stdc++ lib:

```
$ sed -n '3154p' ~/.guix-profile/include/c++/type_traits
  _GLIBCXX20_DEPRECATED("use is_standard_layout_v && is_trivial_v instead")
```

And the gcc search paths on my machine:

```
$ echo | g++ -E -Wp,-v -
ignoring nonexistent directory "/no-gcc-local-prefix/include"
ignoring nonexistent directory
"/gnu/store/ikn0imxfc6n0ba12mrf0c4hc1jm7ylc7-gcc-14.2.0-lib/lib/gcc/x86_64-unknown-linux-gnu/14.2.0/../../../../../../../x86_64-unknown-linux-gnu/include"
ignoring duplicate directory "/home/lgatto/.guix-profile/include"
  as it is a non-system directory that duplicates a system directory
#include "..." search starts here:
#include <...> search starts here:
 /home/lgatto/.guix-profile/include
 
/gnu/store/ikn0imxfc6n0ba12mrf0c4hc1jm7ylc7-gcc-14.2.0-lib/lib/gcc/x86_64-unknown-linux-gnu/14.2.0/include
 
/gnu/store/ikn0imxfc6n0ba12mrf0c4hc1jm7ylc7-gcc-14.2.0-lib/lib/gcc/x86_64-unknown-linux-gnu/14.2.0/include-fixed
 /gnu/store/zvlp3n8iwa1svxmwv4q22pv1pb1c9pjq-glibc-2.39/include
End of search list.
# 0 "<stdin>"
# 0 "<built-in>"
# 0 "<command-line>"
# 1 "/home/lgatto/.guix-profile/include/stdc-predef.h" 1 3
# 0 "<command-line>" 2
# 1 "<stdin>"
````

Except for the version and location, all this looks very similar to
what you have, which leaves me quite puzzled.

Laurent

On Tue, 12 Nov 2024 at 18:54, Fredrik Salomonsson <plattfot@posteo.net> wrote:
>
> Hi,
>
> Laurent Gatto <laurent.gatto@gmail.com> writes:
>
> > 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?
>
> What version is gcc on your main system?  Could be that you somehow are
> running an older gcc than what's in that .guix-profile.
>
> I could compile that example just fine on mine.
>
> Here is how g++ looks like on my machine, maybe that will help.  Note
> that I'm using guix home to install gcc-toolchain.
>
> The version I'm using:
> ```
> $ g++ --version
> g++ (GCC) 11.4.0
> Copyright (C) 2021 Free Software Foundation, Inc.
> This is free software; see the source for copying conditions.  There is NO
> warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> ```
>
> From where I'm picking up g++ from:
> ```
> $ which g++
> /home/plattfot/.guix-home/profile/bin/g++
> ```
>
> Checking the stdc++ lib:
> ```
> $ sed -n '3154p' ~/.guix-home/profile/include/c++/type_traits
>   _GLIBCXX20_DEPRECATED("use is_standard_layout_v && is_trivial_v instead")
> ```
> Which matches what you have.
>
> Here is the search paths gcc uses on my machine:
>
> ```
> $ echo | g++ -E -Wp,-v -
> ignoring nonexistent directory "/no-gcc-local-prefix/include"
> ignoring nonexistent directory 
> "/gnu/store/w0i4fd8ivrpwz91a0wjwz5l0b2ralj16-gcc-11.4.0-lib/lib/gcc/x86_64-unknown-linux-gnu/11.4.0/../../../../../../../x86_64-unknown-linux-gnu/include"
> #include "..." search starts here:
> #include <...> search starts here:
>  /home/plattfot/.guix-home/profile/include
>  
> /gnu/store/w0i4fd8ivrpwz91a0wjwz5l0b2ralj16-gcc-11.4.0-lib/lib/gcc/x86_64-unknown-linux-gnu/11.4.0/include
>  
> /gnu/store/w0i4fd8ivrpwz91a0wjwz5l0b2ralj16-gcc-11.4.0-lib/lib/gcc/x86_64-unknown-linux-gnu/11.4.0/include-fixed
>  /gnu/store/zvlp3n8iwa1svxmwv4q22pv1pb1c9pjq-glibc-2.39/include
> End of search list.
> # 0 "<stdin>"
> # 0 "<built-in>"
> # 0 "<command-line>"
> # 1 "/home/plattfot/.guix-home/profile/include/stdc-predef.h" 1 3
> # 0 "<command-line>" 2
> # 1 "<stdin>"
> ```
> --
> s/Fred[re]+i[ck]+/Fredrik/g