https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120969
--- Comment #7 from Andrew Pinski <pinskia at gcc dot gnu.org> --- From https://gcc.gnu.org/onlinedocs/gcc-15.1.0/gcc/Standards.html#C_002b_002b-Language : Another revised ISO C++ standard was published in 2020 as ISO/IEC 14882:2020, and is referred to as C++20; before its publication it was sometimes referred to as C++2a. GCC supports most of the changes in the new specification. For further details see https://gcc.gnu.org/projects/cxx-status.html#cxx20. To select this standard in GCC, use the option -std=c++20. Note the use of "most" there. compare that to C++17: The C++ language was further revised in 2017 and ISO/IEC 14882:2017 was published. This is referred to as C++17, and before publication was often referred to as C++1z. GCC supports all the changes in that specification. For further details see https://gcc.gnu.org/projects/cxx-status.html#cxx17. Use the option -std=c++17 to select this variant of C++. See how the use of "all" there.
