add clang c_std=c18 alias

fix unit test skips for clang c18

correct unittests clang minimum version

cleanup unittest clang skip c_std

finesse unittest vs. clang version

mesonbuild/compilers/c.py

@@ -89,13 +89,16 @@ class ClangCCompiler(ClangCompiler, CCompiler):
         opts = CCompiler.get_options(self)
         c_stds = ['c89', 'c99', 'c11']
         g_stds = ['gnu89', 'gnu99', 'gnu11']
-        if self.compiler_type is CompilerType.CLANG_OSX:
-            v = '>=10.0.0'
-        else:
-            v = '>=7.0.0'
+        # https://releases.llvm.org/6.0.0/tools/clang/docs/ReleaseNotes.html
+        # https://en.wikipedia.org/wiki/Xcode#Latest_versions
+        v = '>=10.0.0' if self.compiler_type is CompilerType.CLANG_OSX else '>=6.0.0'
         if version_compare(self.version, v):
             c_stds += ['c17']
             g_stds += ['gnu17']
+        v = '>=11.0.0' if self.compiler_type is CompilerType.CLANG_OSX else '>=8.0.0'
+        if version_compare(self.version, v):
+            c_stds += ['c18']
+            g_stds += ['gnu18']
         opts.update({'c_std': coredata.UserComboOption('C language standard to use',
                                                        ['none'] + c_stds + g_stds,
                                                        'none')})

mesonbuild/mesonlib.py

@@ -574,7 +574,7 @@ class Version:
         # otherwise, the version with a suffix remaining is greater
         return comparator(len(self._v), len(other._v))
 
-def _version_extract_cmpop(vstr2):
+def _version_extract_cmpop(vstr2: str) -> tuple:
     if vstr2.startswith('>='):
         cmpop = operator.ge
         vstr2 = vstr2[2:]
@@ -601,7 +601,7 @@ def _version_extract_cmpop(vstr2):
 
     return (cmpop, vstr2)
 
-def version_compare(vstr1, vstr2):
+def version_compare(vstr1: str, vstr2: str) -> bool:
     (cmpop, vstr2) = _version_extract_cmpop(vstr2)
     return cmpop(Version(vstr1), Version(vstr2))
 
@@ -619,7 +619,7 @@ def version_compare_many(vstr1, conditions):
 
 # determine if the minimum version satisfying the condition |condition| exceeds
 # the minimum version for a feature |minimum|
-def version_compare_condition_with_min(condition, minimum):
+def version_compare_condition_with_min(condition, minimum) -> bool:
     if condition.startswith('>='):
         cmpop = operator.le
         condition = condition[2:]

run_unittests.py

@@ -4545,19 +4545,43 @@ class LinuxlikeTests(BasePlatformTests):
 
     def _test_stds_impl(self, testdir, compiler, p):
         lang_std = p + '_std'
-        # Check that all the listed -std=xxx options for this compiler work
-        # just fine when used
+        clangLT5 = (compiler.get_id() == 'clang' and
+                    (version_compare(compiler.version, '<5.0.0') or
+                     (compiler.compiler_type == mesonbuild.compilers.CompilerType.CLANG_OSX and version_compare(compiler.version, '<9.1'))))
+        clangLT6 = (compiler.get_id() == 'clang' and
+                    (version_compare(compiler.version, '<6.0.0') or
+                     (compiler.compiler_type == mesonbuild.compilers.CompilerType.CLANG_OSX and version_compare(compiler.version, '<10.0'))))
+        clangLT8 = (compiler.get_id() == 'clang' and
+                    (version_compare(compiler.version, '<8.0.0') or
+                     (compiler.compiler_type == mesonbuild.compilers.CompilerType.CLANG_OSX and version_compare(compiler.version, '<11.0'))))
+        # Check that all the listed -std=xxx options for this compiler work just fine when used
+        # https://en.wikipedia.org/wiki/Xcode#Latest_versions
+        # https://www.gnu.org/software/gcc/projects/cxx-status.html
         for v in compiler.get_options()[lang_std].choices:
-            if (compiler.get_id() == 'clang' and '17' in v and
-                (version_compare(compiler.version, '<5.0.0') or
-                 (compiler.compiler_type == mesonbuild.compilers.CompilerType.CLANG_OSX and version_compare(compiler.version, '<9.1')))):
-                continue
-            if (compiler.get_id() == 'clang' and '2a' in v and
-                (version_compare(compiler.version, '<6.0.0') or
-                 (compiler.compiler_type == mesonbuild.compilers.CompilerType.CLANG_OSX and version_compare(compiler.version, '<9.1')))):
-                continue
-            if (compiler.get_id() == 'gcc' and '2a' in v and version_compare(compiler.version, '<8.0.0')):
-                continue
+            # we do it like this to handle gnu++17,c++17 and gnu17,c17 cleanly
+            # thus, C++ first
+            if '++17' in v:
+                if clangLT5:
+                    continue
+                if compiler.get_id() == 'gcc' and version_compare(compiler.version, '<5.0.0'):
+                    continue
+            elif '++2a' in v:
+                # https://en.cppreference.com/w/cpp/compiler_support
+                if clangLT6:
+                    continue
+                if compiler.get_id() == 'gcc' and version_compare(compiler.version, '<8.0.0'):
+                    continue
+            # now C
+            elif '17' in v:
+                if clangLT6:
+                    continue
+                if compiler.get_id() == 'gcc' and version_compare(compiler.version, '<8.0.0'):
+                    continue
+            elif '18' in v:
+                if clangLT8:
+                    continue
+                if compiler.get_id() == 'gcc' and version_compare(compiler.version, '<8.0.0'):
+                    continue
             std_opt = '{}={}'.format(lang_std, v)
             self.init(testdir, extra_args=['-D' + std_opt])
             cmd = self.get_compdb()[0]['command']