it looks like the standard is c++ 20. I am still getting the following error message:
/usr/bin/cmake -S/home/albaro/drogon-assist -B/home/albaro/drogon-assist/build --check-build-system CMakeFiles/Makefile.cmake 0
/usr/bin/cmake -E cmake_progress_start /home/albaro/drogon-assist/build/CMakeFiles /home/albaro/drogon-assist/build//CMakeFiles/progress.marks
make -f CMakeFiles/Makefile2 all
make[1]: Entering directory '/home/albaro/drogon-assist/build'
make -f CMakeFiles/drogon_assist.dir/build.make CMakeFiles/drogon_assist.dir/depend
make[2]: Entering directory '/home/albaro/drogon-assist/build'
cd /home/albaro/drogon-assist/build && /usr/bin/cmake -E cmake_depends "Unix Makefiles" /home/albaro/drogon-assist /home/albaro/drogon-assist /home/albaro/drogon-assist/build /home/albaro/drogon-assist/build /home/albaro/drogon-assist/build/CMakeFiles/drogon_assist.dir/DependInfo.cmake --color=
Dependencies file "CMakeFiles/drogon_assist.dir/drogon/assist/passwdhash.cpp.o.d" is newer than depends file "/home/albaro/drogon-assist/build/CMakeFiles/drogon_assist.dir/compiler_depend.internal".
Consolidate compiler generated dependencies of target drogon_assist
make[2]: Leaving directory '/home/albaro/drogon-assist/build'
make -f CMakeFiles/drogon_assist.dir/build.make CMakeFiles/drogon_assist.dir/build
make[2]: Entering directory '/home/albaro/drogon-assist/build'
[ 11%] Building CXX object CMakeFiles/drogon_assist.dir/drogon/assist/passwdhash.cpp.o
/usr/bin/c++ -DHAS_YAML_CPP -I/usr/include/botan-2 -I/home/albaro/drogon-assist/. -std=gnu++20 -MD -MT CMakeFiles/drogon_assist.dir/drogon/assist/passwdhash.cpp.o -MF CMakeFiles/drogon_assist.dir/drogon/assist/passwdhash.cpp.o.d -o CMakeFiles/drogon_assist.dir/drogon/assist/passwdhash.cpp.o -c /home/albaro/drogon-assist/drogon/assist/passwdhash.cpp
/home/albaro/drogon-assist/drogon/assist/passwdhash.cpp: In function ‘std::string drassist::secureRandomString(size_t)’:
/home/albaro/drogon-assist/drogon/assist/passwdhash.cpp:20:15: error: ‘string_view’ does not name a type
20 | const string_view alphabet = "1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
| ^~~~~~~~~~~
/home/albaro/drogon-assist/drogon/assist/passwdhash.cpp:24:22: error: ‘alphabet’ was not declared in this scope
24 | ch = alphabet[secureRandom(0, alphabet.size())];
| ^~~~~~~~
make[2]: *** [CMakeFiles/drogon_assist.dir/build.make:76: CMakeFiles/drogon_assist.dir/drogon/assist/passwdhash.cpp.o] Error 1
make[2]: Leaving directory '/home/albaro/drogon-assist/build'
make[1]: *** [CMakeFiles/Makefile2:83: CMakeFiles/drogon_assist.dir/all] Error 2
make[1]: Leaving directory '/home/albaro/drogon-assist/build'
make: *** [Makefile:136: all] Error 2
Thanks for pointing me in the right direction there might be a problem with gcc.