C, changelog and test for named variadic args

CHANGES

@@ -37,6 +37,7 @@ Features added
   The warnings printed from this functionality can be suppressed by setting
   :confval:`c_warn_on_allowed_pre_v3`` to ``True``.
   The functionality is immediately deprecated.
+* #7999: C, add support for named variadic macro arguments.
 
 Bugs fixed
 ----------

sphinx/domains/c.py

@@ -2922,6 +2922,8 @@ class DefinitionParser(BaseParser):
             if not self.match(identifier_re):
                 self.fail("Expected identifier in macro parameters.")
             nn = ASTNestedName([ASTIdentifier(self.matched_text)], rooted=False)
+            # Allow named variadic args:
+            # https://gcc.gnu.org/onlinedocs/cpp/Variadic-Macros.html
             self.skip_ws()
             if self.skip_string_and_ws('...'):
                 args.append(ASTMacroParameter(nn, False, True))

tests/test_domain_c.py

@@ -296,6 +296,10 @@ def test_macro_definitions():
     check('macro', 'M(arg, ...)', {1: 'M'})
     check('macro', 'M(arg1, arg2, ...)', {1: 'M'})
     check('macro', 'M(arg1, arg2, arg3, ...)', {1: 'M'})
+    # GNU extension
+    check('macro', 'M(arg1, arg2, arg3...)', {1: 'M'})
+    with pytest.raises(DefinitionError):
+        check('macro', 'M(arg1, arg2..., arg3)', {1: 'M'})
 
 
 def test_member_definitions():