Index: lib/StaticAnalyzer/Checkers/DeadStoresChecker.cpp =================================================================== --- lib/StaticAnalyzer/Checkers/DeadStoresChecker.cpp +++ lib/StaticAnalyzer/Checkers/DeadStoresChecker.cpp @@ -401,6 +401,11 @@ // Check for '&'. Any VarDecl whose address has been taken we treat as // escaped. // FIXME: What about references? + if (auto *LE = dyn_cast(S)) { + findLambdaReferenceCaptures(LE); + return; + } + const UnaryOperator *U = dyn_cast(S); if (!U) return; @@ -412,6 +417,28 @@ if (const VarDecl *VD = dyn_cast(DR->getDecl())) Escaped.insert(VD); } + + // Treat local variables captured by reference in C++ lambdas as escaped. + void findLambdaReferenceCaptures(const LambdaExpr *LE) { + const CXXRecordDecl *LambdaClass = LE->getLambdaClass(); + llvm::DenseMap CaptureFields; + FieldDecl *ThisCaptureField; + LambdaClass->getCaptureFields(CaptureFields, ThisCaptureField); + + for (const LambdaCapture &C : LE->captures()) { + if (!C.capturesVariable()) + continue; + + VarDecl *VD = C.getCapturedVar(); + const FieldDecl *FD = CaptureFields[VD]; + if (!FD) + continue; + + // If the capture field is a reference type, it is capture-by-reference. + if (FD->getType()->isReferenceType()) + Escaped.insert(VD); + } + } }; } // end anonymous namespace Index: test/Analysis/lambdas.cpp =================================================================== --- test/Analysis/lambdas.cpp +++ test/Analysis/lambdas.cpp @@ -1,4 +1,4 @@ -// RUN: %clang_cc1 -std=c++11 -fsyntax-only -analyze -analyzer-checker=core,debug.ExprInspection -analyzer-config inline-lambdas=true -verify %s +// RUN: %clang_cc1 -std=c++11 -fsyntax-only -analyze -analyzer-checker=core,deadcode,debug.ExprInspection -analyzer-config inline-lambdas=true -verify %s // RUN: %clang_cc1 -std=c++11 -fsyntax-only -analyze -analyzer-checker=core,debug.DumpCFG -analyzer-config inline-lambdas=true %s > %t 2>&1 // RUN: FileCheck --input-file=%t %s @@ -281,6 +281,49 @@ }(); } +// Lambda capture counts as use for dead-store checking. + +int returnsValue(); + +void captureByCopyCausesUse() { + int local1 = returnsValue(); // no-warning + int local2 = returnsValue(); // no-warning + int local3 = returnsValue(); // expected-warning{{Value stored to 'local3' during its initialization is never read}} + + (void)[local1, local2]() { }; // Explicit capture by copy counts as use. + + int local4 = returnsValue(); // no-warning + int local5 = returnsValue(); // expected-warning{{Value stored to 'local5' during its initialization is never read}} + + (void)[=]() { + (void)local4; // Implicit capture by copy counts as use + }; +} + +void captureByReference() { + int local1 = returnsValue(); // no-warning + + auto lambda1 = [&local1]() { // Explicit capture by reference + local1++; + }; + + // Don't treat as a dead store because local1 was was captured by reference. + local1 = 7; // no-warning + + lambda1(); + + int local2 = returnsValue(); // no-warning + + auto lambda2 = [&]() { + local2++; // Implicit capture by reference + }; + + // Don't treat as a dead store because local2 was was captured by reference. + local2 = 7; // no-warning + + lambda2(); +} + // CHECK: [B2 (ENTRY)] // CHECK: Succs (1): B1