[clang] [webkit.UncountedLambdaCapturesChecker] Detect protectedThis pattern. (PR #120528)

[Rashmi Mudduluru via cfe-commits]

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@@ -180,11 +212,51 @@ class UncountedLambdaCapturesChecker
       } else if (C.capturesThis() && shouldCheckThis) {
         if (ignoreParamVarDecl) // this is always a parameter to this function.
           continue;
-        reportBugOnThisPtr(C);
+        bool hasProtectThis = false;
+        for (const LambdaCapture &OtherCapture : L->captures()) {
+          if (auto *ValueDecl = OtherCapture.getCapturedVar()) {
+            if (protectThis(ValueDecl)) {
+              hasProtectThis = true;
+              break;
+            }
+          }
+        }
+        if (!hasProtectThis)
+          reportBugOnThisPtr(C);
       }
     }
   }
 
+  bool protectThis(const ValueDecl *ValueDecl) const {
+    auto *VD = dyn_cast<VarDecl>(ValueDecl);
+    if (!VD)
+      return false;
+    auto *Init = VD->getInit()->IgnoreParenCasts();
+    if (!Init)
+      return false;
+    auto *BTE = dyn_cast<CXXBindTemporaryExpr>(Init);
+    if (!BTE)
+      return false;
+    auto *CE = dyn_cast_or_null<CXXConstructExpr>(BTE->getSubExpr());
+    if (!CE)
+      return false;
+    auto *Ctor = CE->getConstructor();
+    if (!Ctor)
+      return false;
+    auto clsName = safeGetName(Ctor->getParent());
+    if (!isRefType(clsName) || !CE->getNumArgs())
+      return false;
+    auto *Arg = CE->getArg(0)->IgnoreParenCasts();
+    while (auto *UO = dyn_cast<UnaryOperator>(Arg)) {
+      auto OpCode = UO->getOpcode();
+      if (OpCode == UO_Deref || OpCode == UO_AddrOf)
+        Arg = UO->getSubExpr();
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t-rasmud wrote:

Can we add tests where the Arg isn't `this` and for  `UO_AddrOf`?

https://github.com/llvm/llvm-project/pull/120528