Add c++23 to the list of C++ standards.
diff --git a/mesonbuild/compilers/cpp.py b/mesonbuild/compilers/cpp.py
index b37f8cd..bb2176b 100644
--- a/mesonbuild/compilers/cpp.py
+++ b/mesonbuild/compilers/cpp.py
@@ -210,8 +210,8 @@
         })
         opts[key.evolve('std')].choices = [
             'none', 'c++98', 'c++03', 'c++11', 'c++14', 'c++17', 'c++1z',
-            'c++2a', 'c++20', 'gnu++11', 'gnu++14', 'gnu++17', 'gnu++1z',
-            'gnu++2a', 'gnu++20',
+            'c++2a', 'c++20', 'c++23', 'gnu++11', 'gnu++14', 'gnu++17', 'gnu++1z',
+            'gnu++2a', 'gnu++20', 'gnu++23'
         ]
         if self.info.is_windows() or self.info.is_cygwin():
             opts.update({
@@ -386,8 +386,8 @@
         })
         opts[key].choices = [
             'none', 'c++98', 'c++03', 'c++11', 'c++14', 'c++17', 'c++1z',
-            'c++2a', 'c++20', 'gnu++03', 'gnu++11', 'gnu++14', 'gnu++17',
-            'gnu++1z', 'gnu++2a', 'gnu++20',
+            'c++2a', 'c++20', 'c++23', 'gnu++03', 'gnu++11', 'gnu++14', 'gnu++17',
+            'gnu++1z', 'gnu++2a', 'gnu++20', 'gnu++23',
         ]
         if self.info.is_windows() or self.info.is_cygwin():
             opts.update({