Cannot be built because of bit_variable not defined, reinterpret_cast and no template called "optional"

[KhazAkar]

Hi!
I've tried building your program on openSUSE Tumbleweed using clang++, but it cannot.
Here is the log:

[  4%] Building CXX object CMakeFiles/canviewer.dir/canviewer.cpp.o
In file included from /home/khazakar/downloadedwithgit/canviewer/canviewer.cpp:14:
In file included from /home/khazakar/downloadedwithgit/canviewer/gtkmm/MainWindow.hpp:33:
In file included from /home/khazakar/downloadedwithgit/canviewer/gtkmm/../can/message.h:7:
In file included from /home/khazakar/downloadedwithgit/canviewer/gtkmm/../can/variable.h:8:
In file included from /home/khazakar/downloadedwithgit/canviewer/gtkmm/../can/bit_variable.h:4:
/home/khazakar/downloadedwithgit/canviewer/gtkmm/../can/endian.h:10:20: error: constexpr function never produces a constant expression [-Winvalid-constexpr]
    constexpr bool is_little_endian()
                   ^
/home/khazakar/downloadedwithgit/canviewer/gtkmm/../can/endian.h:13:24: note: reinterpret_cast is not allowed in a constant expression
        uint8_t *ptr = reinterpret_cast<uint8_t*>(&value);
                       ^
/home/khazakar/downloadedwithgit/canviewer/gtkmm/../can/endian.h:20:20: error: constexpr function never produces a constant expression [-Winvalid-constexpr]
    constexpr bool is_big_endian()
                   ^
/home/khazakar/downloadedwithgit/canviewer/gtkmm/../can/endian.h:23:24: note: reinterpret_cast is not allowed in a constant expression
        uint8_t *ptr = reinterpret_cast<uint8_t*>(&value);
                       ^
In file included from /home/khazakar/downloadedwithgit/canviewer/canviewer.cpp:14:
In file included from /home/khazakar/downloadedwithgit/canviewer/gtkmm/MainWindow.hpp:33:
/home/khazakar/downloadedwithgit/canviewer/gtkmm/../can/message.h:17:39: error: no template named 'optional' in namespace 'std'
            using opt_variable = std::optional<variable>;
                                 ~~~~~^
/home/khazakar/downloadedwithgit/canviewer/gtkmm/../can/message.h:50:13: error: unknown type name 'opt_variable'; did you mean 'bit_variable'?
            opt_variable operator[](std::string) const;
            ^~~~~~~~~~~~
            bit_variable
/home/khazakar/downloadedwithgit/canviewer/gtkmm/../can/bit_variable.h:9:11: note: 'bit_variable' declared here
    class bit_variable
          ^
4 errors generated.
make[2]: *** [CMakeFiles/canviewer.dir/build.make:76: CMakeFiles/canviewer.dir/canviewer.cpp.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:83: CMakeFiles/canviewer.dir/all] Error 2
make: *** [Makefile:91: all] Error 2

[serkonda7]

can confirm with g++ 11.2 on Kali

[PhilTheGeek]

can confirm with g++ 13.3 on Ubuntu 24.04