Add support for c++2a and gnu++2a

mesonbuild/compilers/cpp.py

@@ -80,8 +80,8 @@ class ClangCPPCompiler(ClangCompiler, CPPCompiler):
     def get_options(self):
         opts = CPPCompiler.get_options(self)
         opts.update({'cpp_std': coredata.UserComboOption('cpp_std', 'C++ language standard to use',
-                                                         ['none', 'c++98', 'c++03', 'c++11', 'c++14', 'c++17', 'c++1z',
-                                                          'gnu++11', 'gnu++14', 'gnu++17', 'gnu++1z'],
+                                                         ['none', 'c++98', 'c++03', 'c++11', 'c++14', 'c++17', 'c++1z', 'c++2a',
+                                                          'gnu++11', 'gnu++14', 'gnu++17', 'gnu++1z', 'gnu++2a'],
                                                          'none')})
         return opts
 
@@ -139,8 +139,8 @@ class GnuCPPCompiler(GnuCompiler, CPPCompiler):
     def get_options(self):
         opts = CPPCompiler.get_options(self)
         opts.update({'cpp_std': coredata.UserComboOption('cpp_std', 'C++ language standard to use',
-                                                         ['none', 'c++98', 'c++03', 'c++11', 'c++14', 'c++17', 'c++1z',
-                                                          'gnu++03', 'gnu++11', 'gnu++14', 'gnu++17', 'gnu++1z'],
+                                                         ['none', 'c++98', 'c++03', 'c++11', 'c++14', 'c++17', 'c++1z', 'c++2a',
+                                                          'gnu++03', 'gnu++11', 'gnu++14', 'gnu++17', 'gnu++1z', 'gnu++2a'],
                                                          'none'),
                      'cpp_debugstl': coredata.UserBooleanOption('cpp_debugstl',
                                                                 'STL debug mode',

run_unittests.py

@@ -3113,6 +3113,10 @@ class LinuxlikeTests(BasePlatformTests):
                 (version_compare(compiler.version, '<5.0.0') or
                  (compiler.clang_type == mesonbuild.compilers.CLANG_OSX and version_compare(compiler.version, '<9.2')))):
                 continue
+            if (compiler.get_id() == 'clang' and '2a' in v and
+                (version_compare(compiler.version, '<6.0.0') or
+                 (compiler.clang_type == mesonbuild.compilers.CLANG_OSX and version_compare(compiler.version, '<9.2')))):
+                continue
             std_opt = '{}={}'.format(lang_std, v)
             self.init(testdir, ['-D' + std_opt])
             cmd = self.get_compdb()[0]['command']