[WebKit checkers] Add an annotation for pointer conversion. (llvm#141277)

This PR adds the WebKit checker support for
[[clang::annotate_type("webkit.pointerconversion")]].

When this attribute is set on the return value of a function, the
function is treated as safe to call anywhere and the return value's
pointer origin is the argument.`

Author: rniwa

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

@@ -470,6 +470,18 @@ bool isPtrConversion(const FunctionDecl *F) {
       FunctionName == "checked_objc_cast")
     return true;
 
+  auto ReturnType = F->getReturnType();
+  if (auto *Type = ReturnType.getTypePtrOrNull()) {
+    if (auto *AttrType = dyn_cast<AttributedType>(Type)) {
+      if (auto *Attr = AttrType->getAttr()) {
+        if (auto *AnnotateType = dyn_cast<AnnotateTypeAttr>(Attr)) {
+          if (AnnotateType->getAnnotation() == "webkit.pointerconversion")
+            return true;
+        }
+      }
+    }
+  }
+
   return false;
 }
 

clang/test/Analysis/Checkers/WebKit/call-args-safe-functions.cpp

@@ -1,10 +1,12 @@
 // RUN: %clang_analyze_cc1 -analyzer-checker=alpha.webkit.UncountedCallArgsChecker -verify %s
-// expected-no-diagnostics
+
+#include "mock-types.h"
 
 class Base {
 public:
-    inline void ref();
-    inline void deref();
+    void ref();
+    void deref();
+    void doWork();
 };
 
 class Derived : public Base {
@@ -21,6 +23,7 @@ class SubDerived final : public Derived {
 class OtherObject {
 public:
     Derived* obj();
+    Base* base();
 };
 
 class String {
@@ -44,6 +47,12 @@ inline Target* uncheckedDowncast(Source* source)
     return static_cast<Target*>(source);
 }
 
+template<typename Target, typename Source>
+Target* [[clang::annotate_type("webkit.pointerconversion")]] newCastFunction(Source*);
+
+template<typename Target, typename Source>
+Target* [[clang::annotate_type("unrelated-annotation")]] badCastFunction(Source*);
+
 template<typename... Types>
 String toString(const Types&... values);
 
@@ -52,5 +61,17 @@ void foo(OtherObject* other)
     dynamicDowncast<SubDerived>(other->obj());
     checkedDowncast<SubDerived>(other->obj());
     uncheckedDowncast<SubDerived>(other->obj());
+    newCastFunction<SubDerived>(other->obj());
+    badCastFunction<SubDerived>(other->obj());
+    // expected-warning@-1{{Call argument is uncounted and unsafe}}
     toString(other->obj());
 }
+
+struct SomeStruct {
+  Derived* [[clang::annotate_type("webkit.pointerconversion")]] ptrConversion(Base*);
+
+  void foo(OtherObject& otherObj) {
+    RefPtr ptr = otherObj.base();
+    ptrConversion(ptr.get())->doWork();
+  }
+};