[clang] [webkit.UncountedLambdaCapturesChecker] Ignore a lambda which gets called immediately (PR #162977)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang-static-analyzer-1

@llvm/pr-subscribers-clang

Author: Ryosuke Niwa (rniwa)

<details>
<summary>Changes</summary>

Recognize more ways in which a lambda can be declared and called immediately.

---
Full diff: https://github.com/llvm/llvm-project/pull/162977.diff


2 Files Affected:

- (modified) clang/lib/StaticAnalyzer/Checkers/WebKit/RawPtrRefLambdaCapturesChecker.cpp (+10) 
- (modified) clang/test/Analysis/Checkers/WebKit/uncounted-lambda-captures.cpp (+17) 


``````````diff
diff --git a/clang/lib/StaticAnalyzer/Checkers/WebKit/RawPtrRefLambdaCapturesChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/WebKit/RawPtrRefLambdaCapturesChecker.cpp
index 033eb8cc299b0..6b3a4a77e30c7 100644
--- a/clang/lib/StaticAnalyzer/Checkers/WebKit/RawPtrRefLambdaCapturesChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/WebKit/RawPtrRefLambdaCapturesChecker.cpp
@@ -253,6 +253,16 @@ class RawPtrRefLambdaCapturesChecker
         auto *Callee = CE->getCallee();
         if (!Callee)
           return;
+        Callee = Callee->IgnoreParenCasts();
+        if (auto *MTE = dyn_cast<MaterializeTemporaryExpr>(Callee))
+          Callee = MTE->getSubExpr();
+        if (!Callee)
+          return;
+        Callee = Callee->IgnoreParenCasts();
+        if (auto* L = dyn_cast_or_null<LambdaExpr>(Callee)) {
+          LambdasToIgnore.insert(L); // Calling a lambda upon creation is safe.
+          return;
+        }
         auto *DRE = dyn_cast<DeclRefExpr>(Callee->IgnoreParenCasts());
         if (!DRE)
           return;
diff --git a/clang/test/Analysis/Checkers/WebKit/uncounted-lambda-captures.cpp b/clang/test/Analysis/Checkers/WebKit/uncounted-lambda-captures.cpp
index a4ad741182f56..7a8a433e9a7ca 100644
--- a/clang/test/Analysis/Checkers/WebKit/uncounted-lambda-captures.cpp
+++ b/clang/test/Analysis/Checkers/WebKit/uncounted-lambda-captures.cpp
@@ -439,6 +439,23 @@ void capture_copy_in_lambda(CheckedObj& checked) {
   });
 }
 
+struct TemplateFunctionCallsLambda {
+  void ref() const;
+  void deref() const;
+
+  RefCountable* obj();
+
+  template <typename T>
+  RefPtr<T> method(T* t) {
+    auto ret = ([&]() -> RefPtr<T> {
+      if constexpr (T::isEncodable)
+        return t;
+      return obj() ? t : nullptr;
+    })();
+    return ret;
+  }
+};
+
 class Iterator {
 public:
   Iterator(void* array, unsigned long sizeOfElement, unsigned int index);

``````````

</details>


https://github.com/llvm/llvm-project/pull/162977