From 19ec98fd0d08441f41f1b80f1efd1aca64a1917e Mon Sep 17 00:00:00 2001
From: chrchr-github <christian.riesch@live.com>
Date: Mon, 1 Jul 2024 23:00:40 +0200
Subject: [PATCH] Fix #10660 FP: overridden member functions of unknown
 abstract base classes reported as unused

---
 lib/checkunusedfunctions.cpp |  9 +++++++++
 lib/symboldatabase.cpp       |  4 +---
 test/testunusedfunctions.cpp | 24 ++++++++++++++++++++++++
 3 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/lib/checkunusedfunctions.cpp b/lib/checkunusedfunctions.cpp
index 3fc19d340d7..fa914523813 100644
--- a/lib/checkunusedfunctions.cpp
+++ b/lib/checkunusedfunctions.cpp
@@ -85,6 +85,15 @@ void CheckUnusedFunctions::parseTokens(const Tokenizer &tokenizer, const Setting
             if (func->isExtern())
                 continue;
 
+            bool foundAllBaseClasses{};
+            if (const Function* ofunc = func->getOverriddenFunction(&foundAllBaseClasses)) {
+                if (!foundAllBaseClasses || ofunc->isPure())
+                    continue;
+            }
+            else if (func->isImplicitlyVirtual()) {
+                continue;
+            }
+
             mFunctionDecl.emplace_back(func);
 
             FunctionUsage &usage = mFunctions[stripTemplateParameters(func->name())];
diff --git a/lib/symboldatabase.cpp b/lib/symboldatabase.cpp
index 31e54535512..a6d9c9bd928 100644
--- a/lib/symboldatabase.cpp
+++ b/lib/symboldatabase.cpp
@@ -4554,9 +4554,7 @@ void Function::addArguments(const SymbolDatabase *symbolDatabase, const Scope *s
 
 bool Function::isImplicitlyVirtual(bool defaultVal) const
 {
-    if (hasVirtualSpecifier()) //If it has the virtual specifier it's definitely virtual
-        return true;
-    if (hasOverrideSpecifier()) //If it has the override specifier then it's either virtual or not going to compile
+    if (hasVirtualSpecifier() || hasOverrideSpecifier() || hasFinalSpecifier())
         return true;
     bool foundAllBaseClasses = true;
     if (getOverriddenFunction(&foundAllBaseClasses)) //If it overrides a base class's method then it's virtual
diff --git a/test/testunusedfunctions.cpp b/test/testunusedfunctions.cpp
index 2b1773f2f66..4be243363ac 100644
--- a/test/testunusedfunctions.cpp
+++ b/test/testunusedfunctions.cpp
@@ -82,6 +82,7 @@ class TestUnusedFunctions : public TestFixture {
         TEST_CASE(entrypointsUnix);
 
         TEST_CASE(includes);
+        TEST_CASE(virtualFunc);
     }
 
 #define check(...) check_(__FILE__, __LINE__, __VA_ARGS__)
@@ -711,6 +712,29 @@ class TestUnusedFunctions : public TestFixture {
         check(processed);
         TODO_ASSERT_EQUALS("[test.h:3]: (style) The function 'f' is never used.\n", "[test.cpp:3]: (style) The function 'f' is never used.\n", errout_str());
     }
+
+    void virtualFunc()
+    {
+        check("struct D : public B {\n" // #10660
+              "    virtual void f() {}\n"
+              "    void g() override {}\n"
+              "    void h() final {}\n"
+              "};\n");
+        ASSERT_EQUALS("", errout_str());
+
+        check("struct B {\n"
+              "    virtual void f() = 0;\n"
+              "    void g();\n"
+              "};\n"
+              "struct D : B {\n"
+              "    void f() override {}\n"
+              "};\n"
+              "int main() {\n"
+              "    D d;\n"
+              "    d.g();\n"
+              "}\n");
+        ASSERT_EQUALS("", errout_str());
+    }
 };
 
 REGISTER_TEST(TestUnusedFunctions)