C, properly error on keywords as function parameters

CHANGES

@@ -77,6 +77,8 @@ Bugs fixed
   with size explicitly set in pixels) (fixed for ``'pdflatex'/'lualatex'`` only)
 * #8911: C++: remove the longest matching prefix in
   :confval:`cpp_index_common_prefix` instead of the first that matches.
+* C, properly reject function declarations when a keyword is used
+  as parameter name.
 
 Testing
 --------

sphinx/domains/c.py

@@ -2703,6 +2703,9 @@ class DefinitionParser(BaseParser):
                 declId = None
         elif named == 'single':
             if self.match(identifier_re):
+                if self.matched_text in _keywords:
+                    self.fail("Expected identifier, "
+                              "got keyword: %s" % self.matched_text)
                 identifier = ASTIdentifier(self.matched_text)
                 declId = ASTNestedName([identifier], rooted=False)
             else:

tests/test_domain_c.py

@@ -417,6 +417,9 @@ def test_function_definitions():
     check('function', 'void f(int arr[const static volatile 42])', {1: 'f'},
           output='void f(int arr[static volatile const 42])')
 
+    with pytest.raises(DefinitionError):
+        parse('function', 'void f(int for)')
+
 
 def test_nested_name():
     check('struct', '{key}.A', {1: "A"})