[clang] [WebKit checkers] Treat function pointers with "Singleton" suffix as singleton. (PR #158012)

[Ryosuke Niwa via cfe-commits]

https://github.com/rniwa updated https://github.com/llvm/llvm-project/pull/158012

>From 7081e79e160a7393b50437bd7ba2d462b33a330b Mon Sep 17 00:00:00 2001
From: Ryosuke Niwa <rniwa at webkit.org>
Date: Thu, 11 Sep 2025 01:23:50 -0700
Subject: [PATCH] [WebKit checkers] Treat function pointers with "Singleton"
 suffix as singleton.

Also add test cases for a member function pointer and a pointer to static member function.
The former should always emit a warning since we only allow static member function to return a singleton.
---
 .../Checkers/WebKit/ASTUtils.cpp              |  5 ++++
 .../Checkers/WebKit/PtrTypesSemantics.cpp     |  2 +-
 .../Checkers/WebKit/PtrTypesSemantics.h       |  3 +-
 .../Checkers/WebKit/unretained-call-args.mm   | 28 +++++++++++++++++++
 4 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/clang/lib/StaticAnalyzer/Checkers/WebKit/ASTUtils.cpp b/clang/lib/StaticAnalyzer/Checkers/WebKit/ASTUtils.cpp
index 6f13d552b4b44..b629de3254ed3 100644
--- a/clang/lib/StaticAnalyzer/Checkers/WebKit/ASTUtils.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/WebKit/ASTUtils.cpp
@@ -160,6 +160,11 @@ bool tryToFindPtrOrigin(
         if (Name == "__builtin___CFStringMakeConstantString" ||
             Name == "NSClassFromString")
           return callback(E, true);
+      } else if (auto *CalleeE = call->getCallee()) {
+        if (auto *E = dyn_cast<DeclRefExpr>(CalleeE->IgnoreParenCasts())) {
+          if (isSingleton(E->getFoundDecl()))
+            return callback(E, true);
+        }
       }
 
       // Sometimes, canonical type erroneously turns Ref<T> into T.
diff --git a/clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.cpp b/clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.cpp
index 56747d72136e3..90b2343b4be77 100644
--- a/clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.cpp
@@ -479,7 +479,7 @@ bool isTrivialBuiltinFunction(const FunctionDecl *F) {
          Name.starts_with("os_log") || Name.starts_with("_os_log");
 }
 
-bool isSingleton(const FunctionDecl *F) {
+bool isSingleton(const NamedDecl *F) {
   assert(F);
   // FIXME: check # of params == 1
   if (auto *MethodDecl = dyn_cast<CXXMethodDecl>(F)) {
diff --git a/clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.h b/clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.h
index 3c9560cb8059b..d2095d07e1434 100644
--- a/clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.h
+++ b/clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.h
@@ -21,6 +21,7 @@ class CXXMethodDecl;
 class CXXRecordDecl;
 class Decl;
 class FunctionDecl;
+class NamedDecl;
 class QualType;
 class RecordType;
 class Stmt;
@@ -156,7 +157,7 @@ bool isPtrConversion(const FunctionDecl *F);
 bool isTrivialBuiltinFunction(const FunctionDecl *F);
 
 /// \returns true if \p F is a static singleton function.
-bool isSingleton(const FunctionDecl *F);
+bool isSingleton(const NamedDecl *F);
 
 /// An inter-procedural analysis facility that detects functions with "trivial"
 /// behavior with respect to reference counting, such as simple field getters.
diff --git a/clang/test/Analysis/Checkers/WebKit/unretained-call-args.mm b/clang/test/Analysis/Checkers/WebKit/unretained-call-args.mm
index f39822ee2a8c6..75eead070fdf9 100644
--- a/clang/test/Analysis/Checkers/WebKit/unretained-call-args.mm
+++ b/clang/test/Analysis/Checkers/WebKit/unretained-call-args.mm
@@ -438,6 +438,34 @@ void use_const_local() {
 
 } // namespace const_global
 
+namespace var_decl_ref_singleton {
+
+static Class initSomeObject() { return nil; }
+static Class (*getSomeObjectClassSingleton)() = initSomeObject;
+
+bool foo(NSString *obj) {
+  return [obj isKindOfClass:getSomeObjectClassSingleton()];
+}
+
+class Bar {
+public:
+  Class someObject();
+  static Class staticSomeObject();
+};
+typedef Class (Bar::*SomeObjectSingleton)();
+
+bool bar(NSObject *obj, Bar *bar, SomeObjectSingleton someObjSingleton) {
+  return [obj isKindOfClass:(bar->*someObjSingleton)()];
+  // expected-warning at -1{{Call argument for parameter 'aClass' is unretained and unsafe}}
+}
+
+bool baz(NSObject *obj) {
+  Class (*someObjectSingleton)() = Bar::staticSomeObject;
+  return [obj isKindOfClass:someObjectSingleton()];
+}
+
+} // namespace var_decl_ref_singleton
+
 namespace ns_retained_return_value {
 
 NSString *provideNS() NS_RETURNS_RETAINED;