[clang] Use -std=c++23 instead of -std=c++2b

During the ISO C++ Committee meeting plenary session the C++23 Standard
has been voted as technical complete.

This updates the reference to c++2b to c++23 and updates the __cplusplus
macro.

Drive-by fixes c++1z -> c++17 and c++2a -> c++20 when seen.

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D149553

3 files changed, 10 insertions, 8 deletions

diff --git a/clang/docs/CommandGuide/clang.rst b/clang/docs/CommandGuide/clang.rst
index 0722979885af..6c59ffd2ab12 100644
--- a/clang/docs/CommandGuide/clang.rst
+++ b/clang/docs/CommandGuide/clang.rst
@@ -193,13 +193,13 @@ Language Selection and Mode Options
 
    ISO C++ 2020 with amendments and GNU extensions
 
-  | ``c++2b``
+  | ``c++23``
 
-   Working draft for ISO C++ 2023
+   ISO C++ 2023 with amendments
 
-  | ``gnu++2b``
+  | ``gnu++23``
 
-   Working draft for ISO C++ 2023 with GNU extensions
+   ISO C++ 2023 with amendments and GNU extensions
 
  The default C++ language standard is ``gnu++17``.
 
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index ff391c6cb3b9..8fda486228db 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -93,7 +93,7 @@ C++20 Feature Support
   error again in the future once there is a less fragile way to mark a module
   as being part of the implementation rather than a user module.
 
-C++2b Feature Support
+C++23 Feature Support
 ^^^^^^^^^^^^^^^^^^^^^
 
 - Implemented `P2036R3: Change scope of lambda trailing-return-type <https://wg21.link/P2036R3>`_
@@ -181,6 +181,8 @@ Non-comprehensive list of changes in this release
 
 New Compiler Flags
 ------------------
+- The flag ``-std=c++23`` has been added. This behaves the same as the existing
+  flag ``-std=c++2b``.
 
 Deprecated Compiler Flags
 -------------------------
@@ -386,7 +388,7 @@ Bug Fixes to C++ Support
   (`#58674 <https://github.com/llvm/llvm-project/issues/58674>`_)
 - Fix incorrect deletion of the default constructor of unions in some
   cases. (`#48416 <https://github.com/llvm/llvm-project/issues/48416>`_)
-- No longer issue a pre-C++2b compatibility warning in ``-pedantic`` mode
+- No longer issue a pre-C++23 compatibility warning in ``-pedantic`` mode
   regading overloaded `operator[]` with more than one parmeter or for static
   lambdas. (`#61582 <https://github.com/llvm/llvm-project/issues/61582>`_)
 - Stop stripping CV qualifiers from the type of ``this`` when capturing it by value in
diff --git a/clang/docs/StandardCPlusPlusModules.rst b/clang/docs/StandardCPlusPlusModules.rst
index 0b44265374a8..a59a3edbbbac 100644
--- a/clang/docs/StandardCPlusPlusModules.rst
+++ b/clang/docs/StandardCPlusPlusModules.rst
@@ -434,7 +434,7 @@ The following example is not allowed:
 .. code-block:: console
 
   $ clang++ -std=c++20 M.cppm --precompile -o M.pcm
-  $ clang++ -std=c++2b Use.cpp -fprebuilt-module-path=.
+  $ clang++ -std=c++23 Use.cpp -fprebuilt-module-path=.
 
 The compiler would reject the example due to the inconsistent language options.
 Not all options are language options.
@@ -611,7 +611,7 @@ The following describes issues in the current implementation of modules.
 Please see https://github.com/llvm/llvm-project/labels/clang%3Amodules for more issues
 or file a new issue if you don't find an existing one.
 If you're going to create a new issue for standard C++ modules,
-please start the title with ``[C++20] [Modules]`` (or ``[C++2b] [Modules]``, etc)
+please start the title with ``[C++20] [Modules]`` (or ``[C++23] [Modules]``, etc)
 and add the label ``clang:modules`` (if you have permissions for that).
 
 For higher level support for proposals, you could visit https://clang.llvm.org/cxx_status.html.