diff --git a/CHANGES b/CHANGES
index f34d4ae65..7abae4b18 100644
--- a/CHANGES
+++ b/CHANGES
@@ -40,6 +40,8 @@ Incompatible changes
   functions and methods
 * The C domain has been rewritten, with additional directives and roles.
   The existing ones are now more strict, resulting in new warnings.
+* The attribute ``sphinx_cpp_tagname`` in the ``desc_signature_line`` node
+  has been renamed to ``sphinx_line_type``.
 
 Deprecated
 ----------
diff --git a/sphinx/addnodes.py b/sphinx/addnodes.py
index fa04e9344..847a6d715 100644
--- a/sphinx/addnodes.py
+++ b/sphinx/addnodes.py
@@ -119,7 +119,7 @@ class desc_signature_line(nodes.Part, nodes.Inline, nodes.FixedTextElement):
     It should only be used in a ``desc_signature`` with ``is_multiline`` set.
     Set ``add_permalink = True`` for the line that should get the permalink.
     """
-    sphinx_cpp_tagname = ''
+    sphinx_line_type = ''
 
 
 # nodes to use within a desc_signature or desc_signature_line
diff --git a/sphinx/domains/c.py b/sphinx/domains/c.py
index 243f57488..49d1cf6a3 100644
--- a/sphinx/domains/c.py
+++ b/sphinx/domains/c.py
@@ -10,7 +10,7 @@
 
 import re
 from typing import (
-    Any, Callable, Dict, Iterator, List, Tuple, Type, Union
+    Any, Callable, Dict, Iterator, List, Type, Tuple, Union
 )
 from typing import cast
 
@@ -25,7 +25,6 @@ from sphinx.builders import Builder
 from sphinx.directives import ObjectDescription
 from sphinx.domains import Domain, ObjType
 from sphinx.environment import BuildEnvironment
-from sphinx.errors import NoUri
 from sphinx.locale import _, __
 from sphinx.roles import XRefRole
 from sphinx.util import logging
@@ -1220,7 +1219,7 @@ class ASTDeclaration(ASTBase):
         signode['is_multiline'] = True
         # Put each line in a desc_signature_line node.
         mainDeclNode = addnodes.desc_signature_line()
-        mainDeclNode.sphinx_c_tagname = 'declarator'
+        mainDeclNode.sphinx_line_type = 'declarator'
         mainDeclNode['add_permalink'] = not self.symbol.isRedeclaration
         signode += mainDeclNode
 
diff --git a/sphinx/domains/cpp.py b/sphinx/domains/cpp.py
index 639ac20b6..5a85d56a6 100644
--- a/sphinx/domains/cpp.py
+++ b/sphinx/domains/cpp.py
@@ -9,9 +9,8 @@
 """
 
 import re
-import warnings
 from typing import (
-    Any, Callable, Dict, Iterator, List, Match, Pattern, Tuple, Type, TypeVar, Union
+    Any, Callable, Dict, Iterator, List, Tuple, Type, TypeVar, Union
 )
 
 from docutils import nodes, utils
@@ -24,7 +23,6 @@ from sphinx.addnodes import desc_signature, pending_xref
 from sphinx.application import Sphinx
 from sphinx.builders import Builder
 from sphinx.config import Config
-from sphinx.deprecation import RemovedInSphinx40Warning
 from sphinx.directives import ObjectDescription
 from sphinx.domains import Domain, ObjType
 from sphinx.environment import BuildEnvironment
@@ -70,7 +68,7 @@ T = TypeVar('T')
 
     Each signature is in a desc_signature node, where all children are
     desc_signature_line nodes. Each of these lines will have the attribute
-    'sphinx_cpp_tagname' set to one of the following (prioritized):
+    'sphinx_line_type' set to one of the following (prioritized):
     - 'declarator', if the line contains the name of the declared object.
     - 'templateParams', if the line starts a template parameter list,
     - 'templateParams', if the line has template parameters
@@ -1604,7 +1602,7 @@ class ASTTemplateParams(ASTBase):
         def makeLine(parentNode: desc_signature = parentNode) -> addnodes.desc_signature_line:
             signode = addnodes.desc_signature_line()
             parentNode += signode
-            signode.sphinx_cpp_tagname = 'templateParams'
+            signode.sphinx_line_type = 'templateParams'
             return signode
         if self.isNested:
             lineNode = parentNode  # type: Element
@@ -1713,7 +1711,7 @@ class ASTTemplateIntroduction(ASTBase):
         # Note: 'lineSpec' has no effect on template introductions.
         signode = addnodes.desc_signature_line()
         parentNode += signode
-        signode.sphinx_cpp_tagname = 'templateIntroduction'
+        signode.sphinx_line_type = 'templateIntroduction'
         self.concept.describe_signature(signode, 'markType', env, symbol)
         signode += nodes.Text('{')
         first = True
@@ -3416,7 +3414,7 @@ class ASTDeclaration(ASTBase):
         signode['is_multiline'] = True
         # Put each line in a desc_signature_line node.
         mainDeclNode = addnodes.desc_signature_line()
-        mainDeclNode.sphinx_cpp_tagname = 'declarator'
+        mainDeclNode.sphinx_line_type = 'declarator'
         mainDeclNode['add_permalink'] = not self.symbol.isRedeclaration
 
         if self.templatePrefix:
diff --git a/sphinx/util/cfamily.py b/sphinx/util/cfamily.py
index 87e438851..67fdc114b 100644
--- a/sphinx/util/cfamily.py
+++ b/sphinx/util/cfamily.py
@@ -1,10 +1,10 @@
 """
     sphinx.util.cfamily
-    ~~~~~~~~~~~~~~~~
+    ~~~~~~~~~~~~~~~~~~~
 
     Utility functions common to the C and C++ domains.
 
-    :copyright: Copyright 2020-2020 by the Sphinx team, see AUTHORS.
+    :copyright: Copyright 2007-2020 by the Sphinx team, see AUTHORS.
     :license: BSD, see LICENSE for details.
 """
 
@@ -12,7 +12,7 @@ import re
 import warnings
 from copy import deepcopy
 from typing import (
-    Any, Callable, Dict, Iterator, List, Match, Pattern, Tuple, Type, TypeVar, Union
+    Any, Callable, List, Match, Pattern, Tuple
 )
 
 from sphinx.deprecation import RemovedInSphinx40Warning
@@ -244,4 +244,4 @@ class BaseParser:
     def assert_end(self) -> None:
         self.skip_ws()
         if not self.eof:
-            self.fail('Expected end of definition.')
\ No newline at end of file
+            self.fail('Expected end of definition.')