https://github.com/DKLoehr updated
https://github.com/llvm/llvm-project/pull/138741
>From 3fa5eff5f2647185652afd3fc831f6666e3b11fb Mon Sep 17 00:00:00 2001
From: Devon Loehr <dlo...@google.com>
Date: Tue, 6 May 2025 17:28:48 +0000
Subject: [PATCH] Add unnecessary-virtual-specifier to -Wextra
---
clang/docs/ReleaseNotes.rst | 6 +++---
clang/include/clang/Basic/DiagnosticGroups.td | 8 ++++----
llvm/cmake/modules/HandleLLVMOptions.cmake | 5 +++++
3 files changed, 12 insertions(+), 7 deletions(-)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index a4107bfaf913d..498c4f295343c 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -434,9 +434,9 @@ Improvements to Clang's diagnostics
- The ``-Wsign-compare`` warning now treats expressions with bitwise not(~)
and minus(-) as signed integers
except for the case where the operand is an unsigned integer
and throws warning if they are compared with unsigned integers (##18878).
-- The ``-Wunnecessary-virtual-specifier`` warning has been added to warn about
- methods which are marked as virtual inside a ``final`` class, and hence can
- never be overridden.
+- The ``-Wunnecessary-virtual-specifier`` warning (included in ``-Wextra``) has
+ been added to warn about methods which are marked as virtual inside a
+ ``final`` class, and hence can never be overridden.
- Improve the diagnostics for chained comparisons to report actual expressions
and operators (#GH129069).
diff --git a/clang/include/clang/Basic/DiagnosticGroups.td
b/clang/include/clang/Basic/DiagnosticGroups.td
index 1faf8508121f4..bb6e7070b1574 100644
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -421,13 +421,12 @@ def CXX11WarnSuggestOverride :
DiagGroup<"suggest-override">;
def WarnUnnecessaryVirtualSpecifier :
DiagGroup<"unnecessary-virtual-specifier"> {
code Documentation = [{
Warns when a ``final`` class contains a virtual method (including virtual
-destructors). Since ``final`` classes cannot be subclassed, their methods
-cannot be overridden, and hence the ``virtual`` specifier is useless.
+destructors) that does not override anything. Since ``final`` classes cannot
+be subclassed, their methods cannot be overridden, so there is no point to
+introducing new ``virtual`` methods.
The warning also detects virtual methods in classes whose destructor is
``final``, for the same reason.
-
-The warning does not fire on virtual methods which are also marked
``override``.
}];
}
@@ -1163,6 +1162,7 @@ def Extra : DiagGroup<"extra", [
FUseLdPath,
CastFunctionTypeMismatch,
InitStringTooLongMissingNonString,
+ WarnUnnecessaryVirtualSpecifier,
]>;
def Most : DiagGroup<"most", [
diff --git a/llvm/cmake/modules/HandleLLVMOptions.cmake
b/llvm/cmake/modules/HandleLLVMOptions.cmake
index 8b3303fe9f3d2..c427a65ee030c 100644
--- a/llvm/cmake/modules/HandleLLVMOptions.cmake
+++ b/llvm/cmake/modules/HandleLLVMOptions.cmake
@@ -882,6 +882,11 @@ if (LLVM_ENABLE_WARNINGS AND
(LLVM_COMPILER_IS_GCC_COMPATIBLE OR CLANG_CL))
# The LLVM libraries have no stable C++ API, so -Wnoexcept-type is not
useful.
append("-Wno-noexcept-type" CMAKE_CXX_FLAGS)
+ # LLVM has a policy of including virtual "anchor" functions to control
+ # where the vtable is emitted. In `final` classes, these are exactly what
+ # this warning detects: unnecessary virtual methods.
+ add_flag_if_supported("-Wno-unnecessary-virtual-specifier"
CXX_SUPPORTS_UNNECESSARY_VIRTUAL_FLAG)
+
if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
append("-Wnon-virtual-dtor" CMAKE_CXX_FLAGS)
endif()
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