C++ standard

[root@host1 ~]# g++ --version

g++ (GCC) 8.5.0 20210514 (Red Hat 8.5.0-18)

Copyright (C) 2018 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.

[root@host1 ~]# g++ -v --help 2>/dev/null | grep -E "^\s+\-std=.*$"

  -std=<standard>          Assume that the input sources are for <standard>.

  -std=f2003                  Conform to the ISO Fortran 2003 standard.

  -std=f2008                  Conform to the ISO Fortran 2008 standard.

  -std=f2008ts                Conform to the ISO Fortran 2008 standard

  -std=f2018                  Conform to the ISO Fortran 2018 standard.

  -std=f95                    Conform to the ISO Fortran 95 standard.

  -std=gnu                    Conform to nothing in particular.

  -std=legacy                 Accept extensions to support legacy code.

  -std=c++03                  Conform to the ISO 1998 C++ standard revised by

                              -std=c++98.

  -std=c++0x                  Deprecated in favor of -std=c++11.  Same as

                              -std=c++11.

  -std=c++11                  Conform to the ISO 2011 C++ standard.

  -std=c++14                  Conform to the ISO 2014 C++ standard.

  -std=c++17                  Conform to the ISO 2017 C++ standard.

  -std=c++1y                  Deprecated in favor of -std=c++14.  Same as

                              -std=c++14.

  -std=c++1z                  Deprecated in favor of -std=c++17.  Same as

                              -std=c++17.

  -std=c++2a                  Conform to the ISO 2020(?) C++ draft standard

  -std=c++98                  Conform to the ISO 1998 C++ standard revised by

  -std=c11                    Conform to the ISO 2011 C standard.

  -std=c17                    Conform to the ISO 2017 C standard (expected to

  -std=c18                    Conform to the ISO 2017 C standard (expected to

  -std=c1x                    Deprecated in favor of -std=c11.  Same as

                              -std=c11.

  -std=c89                    Conform to the ISO 1990 C standard.  Same as

                              -std=c90.

  -std=c90                    Conform to the ISO 1990 C standard.

  -std=c99                    Conform to the ISO 1999 C standard.

  -std=c9x                    Deprecated in favor of -std=c99.  Same as

                              -std=c99.

  -std=gnu++03                Conform to the ISO 1998 C++ standard revised by

  -std=gnu++0x                Deprecated in favor of -std=gnu++11.  Same as

                              -std=gnu++11.

  -std=gnu++11                Conform to the ISO 2011 C++ standard with GNU

  -std=gnu++14                Conform to the ISO 2014 C++ standard with GNU

  -std=gnu++17                Conform to the ISO 2017 C++ standard with GNU

  -std=gnu++1y                Deprecated in favor of -std=gnu++14.  Same as

                              -std=gnu++14.

  -std=gnu++1z                Deprecated in favor of -std=gnu++17.  Same as

                              -std=gnu++17.

  -std=gnu++2a                Conform to the ISO 2020(?) C++ draft standard

  -std=gnu++98                Conform to the ISO 1998 C++ standard revised by

  -std=gnu11                  Conform to the ISO 2011 C standard with GNU

  -std=gnu17                  Conform to the ISO 2017 C standard (expected to

  -std=gnu18                  Conform to the ISO 2017 C standard (expected to

  -std=gnu1x                  Deprecated in favor of -std=gnu11.  Same as

                              -std=gnu11.

  -std=gnu89                  Conform to the ISO 1990 C standard with GNU

  -std=gnu90                  Conform to the ISO 1990 C standard with GNU

  -std=gnu99                  Conform to the ISO 1999 C standard with GNU

  -std=gnu9x                  Deprecated in favor of -std=gnu99.  Same as

                              -std=gnu99.

  -std=iso9899:1990           Conform to the ISO 1990 C standard.  Same as

                              -std=c90.

  -std=iso9899:199409         Conform to the ISO 1990 C standard as amended in

  -std=iso9899:1999           Conform to the ISO 1999 C standard.  Same as

                              -std=c99.

  -std=iso9899:199x           Deprecated in favor of -std=iso9899:1999.  Same

  -std=iso9899:2011           Conform to the ISO 2011 C standard.  Same as

                              -std=c11.

  -std=iso9899:2017           Conform to the ISO 2017 C standard (expected to

  -std=iso9899:2018           Conform to the ISO 2017 C standard (expected to

[root@host1 ~]#

[root@host1 ~]# echo | g++ -dM -E -x c++ - | grep -F __cplusplus

#define __cplusplus 201402L

[root@host1 ~]# echo | g++ -std=c++03 -dM -E -x c++ - | grep -F __cplusplus

#define __cplusplus 199711L

[root@host1 ~]# echo | g++ -std=c++11 -dM -E -x c++ - | grep -F __cplusplus

#define __cplusplus 201103L