From fa6cc7eadedd61347456f088ef40f6dfdcd751e2 Mon Sep 17 00:00:00 2001
From: Doug Wyatt <doug@sonosphere.com>
Date: Wed, 5 Nov 2025 07:45:33 -0800
Subject: [PATCH] [Clang] FunctionEffects: ignore (methods of) local
 CXXRecordDecls. (#166078)

In the following example, `Functor::method()` inappropriately triggers a
diagnostic that `outer()` is blocking by allocating memory.

```
void outer() [[clang::nonblocking]]
{
	struct Functor {
		int* ptr;

		void method() { ptr = new int; }
	};
}
```

---------

Co-authored-by: Doug Wyatt <dwyatt@apple.com>
---
 clang/lib/Sema/SemaFunctionEffects.cpp        |  8 ++++++++
 .../Sema/attr-nonblocking-constraints.cpp     | 19 +++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/clang/lib/Sema/SemaFunctionEffects.cpp b/clang/lib/Sema/SemaFunctionEffects.cpp
index 4b63eb7df105..12cc02965e7d 100644
--- a/clang/lib/Sema/SemaFunctionEffects.cpp
+++ b/clang/lib/Sema/SemaFunctionEffects.cpp
@@ -1302,6 +1302,14 @@ private:
       return true;
     }
 
+    bool TraverseCXXRecordDecl(CXXRecordDecl *D) override {
+      // Completely skip local struct/class/union declarations since their
+      // methods would otherwise be incorrectly interpreted as part of the
+      // function we are currently traversing. The initial Sema pass will have
+      // already recorded any nonblocking methods needing analysis.
+      return true;
+    }
+
     bool TraverseConstructorInitializer(CXXCtorInitializer *Init) override {
       ViolationSite PrevVS = VSite;
       if (Init->isAnyMemberInitializer())
diff --git a/clang/test/Sema/attr-nonblocking-constraints.cpp b/clang/test/Sema/attr-nonblocking-constraints.cpp
index 881e816292d5..012c017798a1 100644
--- a/clang/test/Sema/attr-nonblocking-constraints.cpp
+++ b/clang/test/Sema/attr-nonblocking-constraints.cpp
@@ -104,6 +104,25 @@ void nb8c()
 	};
 }
 
+void nb8d() [[clang::nonblocking]]
+{
+	// Blocking methods of a local CXXRecordDecl do not generate diagnostics
+	// for the outer function.
+	struct F1 {
+        void method() { void* ptr = new int; }
+	};
+
+	// Skipping the CXXRecordDecl does not skip a following VarDecl.
+	struct F2 {
+        F2() { void* ptr = new int; } // expected-note {{constructor cannot be inferred 'nonblocking' because it allocates or deallocates memory}}
+	} f2; // expected-warning {{function with 'nonblocking' attribute must not call non-'nonblocking' constructor 'nb8d()::F2::F2'}}
+
+	// Nonblocking methods of a local CXXRecordDecl are verified independently.
+	struct F3 {
+		void method() [[clang::nonblocking]] { void* ptr = new int; }// expected-warning {{function with 'nonblocking' attribute must not allocate or deallocate memory}}
+	};
+}
+
 // Make sure template expansions are found and verified.
 	template <typename T>
 	struct Adder {