Fix C coverage support in `sphinx.ext.coverage` (#11591)

CHANGES

@@ -84,6 +84,8 @@ Bugs fixed
 * #11473: Type annotations containing :py:data:`~typing.Literal` enumeration
   values now render correctly.
   Patch by Bénédikt Tran.
+* #11591: Fix support for C coverage in ``sphinx.ext.coverage`` extension.
+  Patch by Stephen Finucane.
 
 Testing
 -------

sphinx/domains/c.py

@@ -77,7 +77,7 @@ _macroKeywords = [
     'thread_local',
 ]
 
-# these are ordered by preceedence
+# these are ordered by precedence
 _expression_bin_ops = [
     ['||', 'or'],
     ['&&', 'and'],

sphinx/ext/coverage.py

@@ -114,8 +114,9 @@ class CoverageBuilder(Builder):
         self.write_c_coverage()
 
     def build_c_coverage(self) -> None:
-        # Fetch all the info from the header files
-        c_objects = self.env.domaindata['c']['objects']
+        c_objects = {}
+        for obj in self.env.domains['c'].get_objects():
+            c_objects[obj[2]] = obj[1]
         for filename in self.c_sourcefiles:
             undoc: set[tuple[str, str]] = set()
             with open(filename, encoding="utf-8") as f:
@@ -124,7 +125,11 @@ class CoverageBuilder(Builder):
                         match = regex.match(line)
                         if match:
                             name = match.groups()[0]
-                            if name not in c_objects:
+                            if key not in c_objects:
+                                undoc.add((key, name))
+                                continue
+
+                            if name not in c_objects[key]:
                                 for exp in self.c_ignorexps.get(key, []):
                                     if exp.match(name):
                                         break

tests/roots/test-root/objects.txt

@@ -133,6 +133,8 @@ C items
 
 .. c:var:: int sphinx_global
 
+.. c:function:: PyObject* Py_SphinxFoo(void)
+
 
 Javascript items
 ================

tests/roots/test-root/special/api.h

@@ -1 +1,2 @@
-PyAPI_FUNC(PyObject *) Py_SphinxTest();
+PyAPI_FUNC(PyObject *) Py_SphinxTest(void);
+PyAPI_FUNC(PyObject *) Py_SphinxFoo(void);