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

2 files changed, 10 insertions, 7 deletions

diff --git a/mesonbuild/compilers/c.py b/mesonbuild/compilers/c.py
index 3b58a07..fb2f8c5 100644
--- a/mesonbuild/compilers/c.py
+++ b/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')})
diff --git a/mesonbuild/mesonlib.py b/mesonbuild/mesonlib.py
index d052a2b..485a0e1 100644
--- a/mesonbuild/mesonlib.py
+++ b/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:]