[clang] [Clang] SemaFunctionEffects: Fix bug where lambdas produced by template expansion weren't verified. (PR #116505)

[Doug Wyatt via cfe-commits]

https://github.com/dougsonos updated https://github.com/llvm/llvm-project/pull/116505

>From d235d3ea8bb3cabfc8db9d87233455a93fa23c05 Mon Sep 17 00:00:00 2001
From: Doug Wyatt <dwyatt at apple.com>
Date: Sat, 16 Nov 2024 11:59:03 -0800
Subject: [PATCH 1/2] [Clang] SemaFunctionEffects: Fix bug where lambdas
 produced by template expansion were not verified.

---
 clang/lib/Sema/SemaFunctionEffects.cpp          |  3 ++-
 clang/lib/Sema/SemaLambda.cpp                   |  3 +--
 .../test/Sema/attr-nonblocking-constraints.cpp  | 17 +++++++++++++++++
 3 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/clang/lib/Sema/SemaFunctionEffects.cpp b/clang/lib/Sema/SemaFunctionEffects.cpp
index 4b5ddb74b1262f..6fe4d2353a2282 100644
--- a/clang/lib/Sema/SemaFunctionEffects.cpp
+++ b/clang/lib/Sema/SemaFunctionEffects.cpp
@@ -807,7 +807,8 @@ class Analyzer {
 
     auto MaybeAddTemplateNote = [&](const Decl *D) {
       if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
-        while (FD != nullptr && FD->isTemplateInstantiation()) {
+        while (FD != nullptr && FD->isTemplateInstantiation() &&
+               FD->getPointOfInstantiation().isValid()) {
           S.Diag(FD->getPointOfInstantiation(),
                  diag::note_func_effect_from_template);
           FD = FD->getTemplateInstantiationPattern();
diff --git a/clang/lib/Sema/SemaLambda.cpp b/clang/lib/Sema/SemaLambda.cpp
index e7afa0f4c81fc4..a67c0b2b367d1a 100644
--- a/clang/lib/Sema/SemaLambda.cpp
+++ b/clang/lib/Sema/SemaLambda.cpp
@@ -1950,8 +1950,6 @@ ExprResult Sema::ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body) {
   LambdaScopeInfo LSI = *cast<LambdaScopeInfo>(FunctionScopes.back());
   ActOnFinishFunctionBody(LSI.CallOperator, Body);
 
-  maybeAddDeclWithEffects(LSI.CallOperator);
-
   return BuildLambdaExpr(StartLoc, Body->getEndLoc(), &LSI);
 }
 
@@ -2284,6 +2282,7 @@ ExprResult Sema::BuildLambdaExpr(SourceLocation StartLoc, SourceLocation EndLoc,
     case ExpressionEvaluationContext::PotentiallyEvaluatedIfUsed:
       break;
     }
+    maybeAddDeclWithEffects(LSI->CallOperator);
   }
 
   return MaybeBindToTemporary(Lambda);
diff --git a/clang/test/Sema/attr-nonblocking-constraints.cpp b/clang/test/Sema/attr-nonblocking-constraints.cpp
index cc9108c0a4fbd6..87cbcc9713859f 100644
--- a/clang/test/Sema/attr-nonblocking-constraints.cpp
+++ b/clang/test/Sema/attr-nonblocking-constraints.cpp
@@ -144,6 +144,23 @@ void nb9() [[clang::nonblocking]]
 		expected-note {{in template expansion here}}
 }
 
+// Make sure we verify lambdas produced from template expansions.
+struct HasTemplatedLambda {
+	void (*fptr)() [[clang::nonblocking]];
+
+	template <typename C>
+	HasTemplatedLambda(const C&)
+		: fptr{ []() [[clang::nonblocking]] {
+			auto* y = new int; // expected-warning {{lambda with 'nonblocking' attribute must not allocate or deallocate memory}}
+		} }
+	{}
+};
+
+void nb9a()
+{
+	HasTemplatedLambda bad(42);
+}
+
 void nb10(
 	void (*fp1)(), // expected-note {{function pointer cannot be inferred 'nonblocking'}}
 	void (*fp2)() [[clang::nonblocking]]

>From a2e28fb65ab0b9f134793dfdc91ec564e65561e7 Mon Sep 17 00:00:00 2001
From: Doug Wyatt <dwyatt at apple.com>
Date: Sat, 16 Nov 2024 17:39:24 -0800
Subject: [PATCH 2/2] Add more tests.

---
 .../test/Sema/attr-nonblocking-constraints.cpp | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/clang/test/Sema/attr-nonblocking-constraints.cpp b/clang/test/Sema/attr-nonblocking-constraints.cpp
index 87cbcc9713859f..bbc909f627f4c3 100644
--- a/clang/test/Sema/attr-nonblocking-constraints.cpp
+++ b/clang/test/Sema/attr-nonblocking-constraints.cpp
@@ -161,6 +161,24 @@ void nb9a()
 	HasTemplatedLambda bad(42);
 }
 
+// Templated function and lambda.
+template <typename T>
+void TemplatedFunc(T x) [[clang::nonblocking]] {
+	auto* ptr = new T; // expected-warning {{function with 'nonblocking' attribute must not allocate or deallocate memory}}
+}
+
+void nb9b() [[clang::nonblocking]] {
+	TemplatedFunc(42); // expected-note {{in template expansion here}}
+
+	auto foo = [](auto x) [[clang::nonblocking]] {
+		auto* ptr = new int; // expected-warning {{lambda with 'nonblocking' attribute must not allocate or deallocate memory}}
+		return x;
+	};
+
+	// Note that foo() won't be validated unless instantiated.
+	foo(42);
+}
+
 void nb10(
 	void (*fp1)(), // expected-note {{function pointer cannot be inferred 'nonblocking'}}
 	void (*fp2)() [[clang::nonblocking]]