[clang] [WebKit checkers] Treat std::bit_cast as a pointer conversion (PR #137476)

[Ryosuke Niwa via cfe-commits]

https://github.com/rniwa created https://github.com/llvm/llvm-project/pull/137476

WebKit repalced its use of WTF::bitwise_cast with std::bit_cast. Add the support for recognizing it as a pointer conversion.

>From c76e86105b5ba03cc2a3c8399670b2b38eb8e6ea Mon Sep 17 00:00:00 2001
From: Ryosuke Niwa <rniwa at webkit.org>
Date: Sat, 26 Apr 2025 14:03:13 -0700
Subject: [PATCH] [WebKit checkers] Treat std::bit_cast as a pointer conversion

WebKit repalced its use of WTF::bitwise_cast with std::bit_cast.
Add the support for recognizing it as a pointer conversion.
---
 .../Checkers/WebKit/PtrTypesSemantics.cpp      |  2 +-
 .../Checkers/WebKit/call-args-checked-ptr.cpp  |  8 ++++----
 .../Analysis/Checkers/WebKit/call-args.cpp     | 18 +++++++++---------
 .../Checkers/WebKit/uncounted-obj-arg.cpp      |  5 +++++
 4 files changed, 19 insertions(+), 14 deletions(-)

diff --git a/clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.cpp b/clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.cpp
index d7111bcb35115..edcf8e4feae4f 100644
--- a/clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.cpp
@@ -462,7 +462,7 @@ bool isPtrConversion(const FunctionDecl *F) {
   const auto FunctionName = safeGetName(F);
   if (FunctionName == "getPtr" || FunctionName == "WeakPtr" ||
       FunctionName == "dynamicDowncast" || FunctionName == "downcast" ||
-      FunctionName == "checkedDowncast" ||
+      FunctionName == "checkedDowncast" || FunctionName == "bit_cast" ||
       FunctionName == "uncheckedDowncast" || FunctionName == "bitwise_cast" ||
       FunctionName == "bridge_cast" || FunctionName == "bridge_id_cast" ||
       FunctionName == "dynamic_cf_cast" || FunctionName == "checked_cf_cast" ||
diff --git a/clang/test/Analysis/Checkers/WebKit/call-args-checked-ptr.cpp b/clang/test/Analysis/Checkers/WebKit/call-args-checked-ptr.cpp
index 59f247d6d007c..d539891ed832d 100644
--- a/clang/test/Analysis/Checkers/WebKit/call-args-checked-ptr.cpp
+++ b/clang/test/Analysis/Checkers/WebKit/call-args-checked-ptr.cpp
@@ -173,14 +173,14 @@ namespace param_formarding_function {
 
   namespace casts {
 
-  CheckedObj* downcast(CheckedObj*) { return nullptr; }
-
-  template<class T>
-  T* bitwise_cast(T*) { return nullptr; }
+  CheckedObj* downcast(CheckedObj*);
+  template<class T> T* bitwise_cast(T*);
+  template<class T> T* bit_cast(T*);
 
     void foo(CheckedObj* param) {
       consume_ref_countable_ptr(downcast(param));
       consume_ref_countable_ptr(bitwise_cast(param));
+      consume_ref_countable_ptr(bit_cast(param));
      }
   }
 }
diff --git a/clang/test/Analysis/Checkers/WebKit/call-args.cpp b/clang/test/Analysis/Checkers/WebKit/call-args.cpp
index d95ae9216edcf..1a8bde29080ac 100644
--- a/clang/test/Analysis/Checkers/WebKit/call-args.cpp
+++ b/clang/test/Analysis/Checkers/WebKit/call-args.cpp
@@ -173,15 +173,15 @@ namespace param_formarding_function {
 
   namespace casts {
 
-  RefCountable* downcast(RefCountable*) { return nullptr; }
-
-  template<class T>
-  T* bitwise_cast(T*) { return nullptr; }
-
-    void foo(RefCountable* param) {
-      consume_ref_countable_ptr(downcast(param));
-      consume_ref_countable_ptr(bitwise_cast(param));
-     }
+  RefCountable* downcast(RefCountable*);
+  template<class T> T* bitwise_cast(T*);
+  template<class T> T* bit_cast(T*);
+
+  void foo(RefCountable* param) {
+    consume_ref_countable_ptr(downcast(param));
+    consume_ref_countable_ptr(bitwise_cast(param));
+    consume_ref_countable_ptr(bit_cast(param));
+   }
   }
 }
 
diff --git a/clang/test/Analysis/Checkers/WebKit/uncounted-obj-arg.cpp b/clang/test/Analysis/Checkers/WebKit/uncounted-obj-arg.cpp
index 69842264af56b..2c6ccb55e2ce8 100644
--- a/clang/test/Analysis/Checkers/WebKit/uncounted-obj-arg.cpp
+++ b/clang/test/Analysis/Checkers/WebKit/uncounted-obj-arg.cpp
@@ -77,6 +77,9 @@ T&& forward(T& arg);
 template<typename T>
 T&& move( T&& t );
 
+template<typename ToType, typename FromType>
+ToType bit_cast(FromType from);
+
 #define offsetof(t, d) __builtin_offsetof(t, d)
 
 } // namespace std
@@ -386,6 +389,7 @@ class RefCounted {
   void trivial68() { point pt = { 1.0 }; }
   unsigned trivial69() { return offsetof(OtherObj, children); }
   DerivedNumber* trivial70() { [[clang::suppress]] return static_cast<DerivedNumber*>(number); }
+  unsigned trivial71() { return std::bit_cast<unsigned>(nullptr); }
 
   static RefCounted& singleton() {
     static RefCounted s_RefCounted;
@@ -577,6 +581,7 @@ class UnrelatedClass {
     getFieldTrivial().trivial68(); // no-warning
     getFieldTrivial().trivial69(); // no-warning
     getFieldTrivial().trivial70(); // no-warning
+    getFieldTrivial().trivial71(); // no-warning
 
     RefCounted::singleton().trivial18(); // no-warning
     RefCounted::singleton().someFunction(); // no-warning