[WebKit checkers] Don't treat virtual functions as safe. (llvm#129632)

Prior to this PR, WebKit checkers erroneously treated functions to be
safe if it has a trivial body even if it was marked as virtual. In the
case of a virtual function, it can have an override which does not pass
the triviality check so we must not make such an assumption.

This PR also restricts the allowed operator overloading while finding
the pointer origin to just operators on smart pointer types: Ref,
RefPtr, CheckedRef, CheckedPtr, RetainPtr, WeakPtr, WeakRef, unique_ptr,
and UniqueRef.

Author: rniwa

clang/lib/StaticAnalyzer/Checkers/WebKit/ASTUtils.cpp

@@ -91,9 +91,17 @@ bool tryToFindPtrOrigin(
       }
 
       if (auto *operatorCall = dyn_cast<CXXOperatorCallExpr>(E)) {
-        if (operatorCall->getNumArgs() == 1) {
-          E = operatorCall->getArg(0);
-          continue;
+        if (auto *Callee = operatorCall->getDirectCallee()) {
+          auto ClsName = safeGetName(Callee->getParent());
+          if (isRefType(ClsName) || isCheckedPtr(ClsName) ||
+              isRetainPtr(ClsName) || ClsName == "unique_ptr" ||
+              ClsName == "UniqueRef" || ClsName == "WeakPtr" ||
+              ClsName == "WeakRef") {
+            if (operatorCall->getNumArgs() == 1) {
+              E = operatorCall->getArg(0);
+              continue;
+            }
+          }
         }
       }
 
@@ -215,7 +223,7 @@ bool EnsureFunctionAnalysis::isACallToEnsureFn(const clang::Expr *E) const {
   if (!Callee)
     return false;
   auto *Body = Callee->getBody();
-  if (!Body)
+  if (!Body || Callee->isVirtualAsWritten())
     return false;
   auto [CacheIt, IsNew] = Cache.insert(std::make_pair(Callee, false));
   if (IsNew)

clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.cpp

@@ -480,6 +480,10 @@ class TrivialFunctionAnalysisVisitor
   TrivialFunctionAnalysisVisitor(CacheTy &Cache) : Cache(Cache) {}
 
   bool IsFunctionTrivial(const Decl *D) {
+    if (auto *FnDecl = dyn_cast<FunctionDecl>(D)) {
+      if (FnDecl->isVirtualAsWritten())
+        return false;
+    }
     return WithCachedResult(D, [&]() {
       if (auto *CtorDecl = dyn_cast<CXXConstructorDecl>(D)) {
         for (auto *CtorInit : CtorDecl->inits()) {

clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.h

@@ -131,6 +131,9 @@ bool isRefType(const std::string &Name);
 /// \returns true if \p Name is CheckedRef or CheckedPtr, false if not.
 bool isCheckedPtr(const std::string &Name);
 
+/// \returns true if \p Name is RetainPtr or its variant, false if not.
+bool isRetainPtr(const std::string &Name);
+
 /// \returns true if \p M is getter of a ref-counted class, false if not.
 std::optional<bool> isGetterOfSafePtr(const clang::CXXMethodDecl *Method);
 

clang/lib/StaticAnalyzer/Checkers/WebKit/RawPtrRefCallArgsChecker.cpp

@@ -175,7 +175,7 @@ class RawPtrRefCallArgsChecker
     if (BR->getSourceManager().isInSystemHeader(CE->getExprLoc()))
       return true;
 
-    if (Callee && TFA.isTrivial(Callee))
+    if (Callee && TFA.isTrivial(Callee) && !Callee->isVirtualAsWritten())
       return true;
 
     if (CE->getNumArgs() == 0)

clang/test/Analysis/Checkers/WebKit/uncounted-local-vars.cpp

@@ -464,4 +464,17 @@ namespace local_var_for_singleton {
     RefCountable* bar = singleton();
     RefCountable* baz = otherSingleton();
   }
+}
+
+namespace virtual_function {
+  struct SomeObject {
+    virtual RefCountable* provide() { return nullptr; }
+    virtual RefCountable* operator&() { return nullptr; }
+  };
+  void foo(SomeObject* obj) {
+    auto* bar = obj->provide();
+    // expected-warning@-1{{Local variable 'bar' is uncounted and unsafe [alpha.webkit.UncountedLocalVarsChecker]}}
+    auto* baz = &*obj;
+    // expected-warning@-1{{Local variable 'baz' is uncounted and unsafe [alpha.webkit.UncountedLocalVarsChecker]}}
+  }
 }

clang/test/Analysis/Checkers/WebKit/uncounted-obj-arg.cpp

@@ -196,6 +196,10 @@ class ComplexNumber {
   ComplexNumber& operator+();
 
   const Number& real() const { return realPart; }
+  const Number& complex() const;
+
+  void ref() const;
+  void deref() const;
 
 private:
   Number realPart;
@@ -240,6 +244,11 @@ class SomeType : public BaseType {
   using BaseType::BaseType;
 };
 
+struct OtherObj {
+  unsigned v { 0 };
+  OtherObj* children[4] { nullptr };
+};
+
 void __libcpp_verbose_abort(const char *__format, ...);
 
 class RefCounted {
@@ -375,7 +384,7 @@ class RefCounted {
     double y;
   };
   void trivial68() { point pt = { 1.0 }; }
-  unsigned trivial69() { return offsetof(RefCounted, children); }
+  unsigned trivial69() { return offsetof(OtherObj, children); }
   DerivedNumber* trivial70() { [[clang::suppress]] return static_cast<DerivedNumber*>(number); }
 
   static RefCounted& singleton() {
@@ -467,6 +476,8 @@ class RefCounted {
   unsigned nonTrivial22() { return ComplexNumber(123, "456").real().value(); }
   unsigned nonTrivial23() { return DerivedNumber("123").value(); }
   SomeType nonTrivial24() { return SomeType("123"); }
+  virtual void nonTrivial25() { }
+  virtual ComplexNumber* operator->() { return nullptr; }
 
   static unsigned s_v;
   unsigned v { 0 };
@@ -642,6 +653,10 @@ class UnrelatedClass {
     // expected-warning@-1{{Call argument for 'this' parameter is uncounted and unsafe}}
     getFieldTrivial().nonTrivial24();
     // expected-warning@-1{{Call argument for 'this' parameter is uncounted and unsafe}}
+    getFieldTrivial().nonTrivial25();
+    // expected-warning@-1{{Call argument for 'this' parameter is uncounted and unsafe}}
+    getFieldTrivial()->complex();
+    // expected-warning@-1{{Call argument for 'this' parameter is uncounted and unsafe}}
   }
 
   void setField(RefCounted*);