[clang] [Clang] Check for uninitialized use in lambda within CXXOperatorCallExpr (PR #129198)

[via cfe-commits]

https://github.com/zhaohuiw42 updated https://github.com/llvm/llvm-project/pull/129198

>From 54c65ab88fe949bce2b1717f97132c06ec1405ac Mon Sep 17 00:00:00 2001
From: zhaohui <zhaohuiw94 at gmail.com>
Date: Fri, 28 Feb 2025 14:12:39 +0800
Subject: [PATCH] [Clang] Check for uninitialized use in lambda within
 CXXOperatorCallExpr

---
 clang/docs/ReleaseNotes.rst          |  1 +
 clang/lib/Sema/SemaDecl.cpp          | 17 +++++++++++++++++
 clang/test/SemaCXX/uninitialized.cpp |  4 ++++
 3 files changed, 22 insertions(+)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 7873c2048e53c..b04eac75440c5 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -255,6 +255,7 @@ Bug Fixes to C++ Support
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^
 - Fixed type checking when a statement expression ends in an l-value of atomic type. (#GH106576)
+- Fixed uninitialized use check in a lambda within CXXOperatorCallExpr. (#GH129198)
 
 Miscellaneous Bug Fixes
 ^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 86e65e56accc8..2066ccab2c4ff 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -60,6 +60,7 @@
 #include "llvm/ADT/STLForwardCompat.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringExtras.h"
+#include "llvm/Support/SaveAndRestore.h"
 #include "llvm/TargetParser/Triple.h"
 #include <algorithm>
 #include <cstring>
@@ -12597,6 +12598,7 @@ namespace {
     bool isRecordType;
     bool isPODType;
     bool isReferenceType;
+    bool isInCXXOperatorCall;
 
     bool isInitList;
     llvm::SmallVector<unsigned, 4> InitFieldIndex;
@@ -12609,6 +12611,7 @@ namespace {
       isPODType = false;
       isRecordType = false;
       isReferenceType = false;
+      isInCXXOperatorCall = false;
       isInitList = false;
       if (ValueDecl *VD = dyn_cast<ValueDecl>(OrigDecl)) {
         isPODType = VD->getType().isPODType(S.Context);
@@ -12796,6 +12799,7 @@ namespace {
     }
 
     void VisitCXXOperatorCallExpr(CXXOperatorCallExpr *E) {
+      llvm::SaveAndRestore cxxOpCallScope(isInCXXOperatorCall, true);
       Expr *Callee = E->getCallee();
 
       if (isa<UnresolvedLookupExpr>(Callee))
@@ -12806,6 +12810,19 @@ namespace {
         HandleValue(Arg->IgnoreParenImpCasts());
     }
 
+    void VisitLambdaExpr(LambdaExpr *E) {
+      if (!isInCXXOperatorCall) {
+        Inherited::VisitLambdaExpr(E);
+        return;
+      }
+
+      for (const auto &init : E->capture_inits())
+        if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(init))
+          HandleDeclRefExpr(DRE);
+        else
+          Visit(init);
+    }
+
     void VisitUnaryOperator(UnaryOperator *E) {
       // For POD record types, addresses of its own members are well-defined.
       if (E->getOpcode() == UO_AddrOf && isRecordType &&
diff --git a/clang/test/SemaCXX/uninitialized.cpp b/clang/test/SemaCXX/uninitialized.cpp
index 4af2c998f082e..654d955b3cc72 100644
--- a/clang/test/SemaCXX/uninitialized.cpp
+++ b/clang/test/SemaCXX/uninitialized.cpp
@@ -892,6 +892,10 @@ namespace lambdas {
       return a1.x;
     });
     A a2([&] { return a2.x; }); // ok
+    A a3([=]{ return a3.x; }()); // expected-warning{{variable 'a3' is uninitialized when used within its own initialization}}
+    A a4([&]{ return a4.x; }()); // expected-warning{{variable 'a4' is uninitialized when used within its own initialization}}
+    A a5([&]{ return a5; }()); // expected-warning{{variable 'a5' is uninitialized when used within its own initialization}}
+    A a6([&]{ return a5.x; }()); // ok
   }
 }