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//===------------- Aliasing.cpp - clang-tidy ------------------------------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include "Aliasing.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExprCXX.h"
namespace clang {
namespace tidy {
namespace utils {
/// Return whether \p S is a reference to the declaration of \p Var.
static bool isAccessForVar(const Stmt *S, const VarDecl *Var) {
if (const auto *DRE = dyn_cast<DeclRefExpr>(S))
return DRE->getDecl() == Var;
return false;
static bool capturesByRef(const CXXRecordDecl *RD, const VarDecl *Var) {
return llvm::any_of(RD->captures(), [Var](const LambdaCapture &C) {
return C.capturesVariable() && C.getCaptureKind() == LCK_ByRef &&
C.getCapturedVar() == Var;
/// Return whether \p Var has a pointer or reference in \p S.
static bool isPtrOrReferenceForVar(const Stmt *S, const VarDecl *Var) {
// Treat block capture by reference as a form of taking a reference.
if (Var->isEscapingByref())
return true;
if (const auto *DS = dyn_cast<DeclStmt>(S)) {
for (const Decl *D : DS->getDeclGroup()) {
if (const auto *LeftVar = dyn_cast<VarDecl>(D)) {
if (LeftVar->hasInit() && LeftVar->getType()->isReferenceType()) {
return isAccessForVar(LeftVar->getInit(), Var);
} else if (const auto *UnOp = dyn_cast<UnaryOperator>(S)) {
if (UnOp->getOpcode() == UO_AddrOf)
return isAccessForVar(UnOp->getSubExpr(), Var);
} else if (const auto *LE = dyn_cast<LambdaExpr>(S)) {
// Treat lambda capture by reference as a form of taking a reference.
return capturesByRef(LE->getLambdaClass(), Var);
} else if (const auto *ILE = dyn_cast<InitListExpr>(S)) {
return llvm::any_of(ILE->inits(), [Var](const Expr *ChildE) {
// If the child expression is a reference to Var, this means that it's
// used as an initializer of a reference-typed field. Otherwise
// it would have been surrounded with an implicit lvalue-to-rvalue cast.
return isAccessForVar(ChildE, Var);
return false;
/// Return whether \p Var has a pointer or reference in \p S.
static bool hasPtrOrReferenceInStmt(const Stmt *S, const VarDecl *Var) {
if (isPtrOrReferenceForVar(S, Var))
return true;
for (const Stmt *Child : S->children()) {
if (!Child)
if (hasPtrOrReferenceInStmt(Child, Var))
return true;
return false;
static bool refersToEnclosingLambdaCaptureByRef(const Decl *Func,
const VarDecl *Var) {
const auto *MD = dyn_cast<CXXMethodDecl>(Func);
if (!MD)
return false;
const CXXRecordDecl *RD = MD->getParent();
if (!RD->isLambda())
return false;
return capturesByRef(RD, Var);
bool hasPtrOrReferenceInFunc(const Decl *Func, const VarDecl *Var) {
return hasPtrOrReferenceInStmt(Func->getBody(), Var) ||
refersToEnclosingLambdaCaptureByRef(Func, Var);
} // namespace utils
} // namespace tidy
} // namespace clang