1 //===------------- Aliasing.cpp - clang-tidy ------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8
9 #include "Aliasing.h"
10
11 #include "clang/AST/Expr.h"
12 #include "clang/AST/ExprCXX.h"
13
14 namespace clang::tidy::utils {
15
16 /// Return whether \p S is a reference to the declaration of \p Var.
isAccessForVar(const Stmt * S,const VarDecl * Var)17 static bool isAccessForVar(const Stmt *S, const VarDecl *Var) {
18 if (const auto *DRE = dyn_cast<DeclRefExpr>(S))
19 return DRE->getDecl() == Var;
20
21 return false;
22 }
23
capturesByRef(const CXXRecordDecl * RD,const VarDecl * Var)24 static bool capturesByRef(const CXXRecordDecl *RD, const VarDecl *Var) {
25 return llvm::any_of(RD->captures(), [Var](const LambdaCapture &C) {
26 return C.capturesVariable() && C.getCaptureKind() == LCK_ByRef &&
27 C.getCapturedVar() == Var;
28 });
29 }
30
31 /// Return whether \p Var has a pointer or reference in \p S.
isPtrOrReferenceForVar(const Stmt * S,const VarDecl * Var)32 static bool isPtrOrReferenceForVar(const Stmt *S, const VarDecl *Var) {
33 // Treat block capture by reference as a form of taking a reference.
34 if (Var->isEscapingByref())
35 return true;
36
37 if (const auto *DS = dyn_cast<DeclStmt>(S)) {
38 for (const Decl *D : DS->getDeclGroup()) {
39 if (const auto *LeftVar = dyn_cast<VarDecl>(D)) {
40 if (LeftVar->hasInit() && LeftVar->getType()->isReferenceType()) {
41 return isAccessForVar(LeftVar->getInit(), Var);
42 }
43 }
44 }
45 } else if (const auto *UnOp = dyn_cast<UnaryOperator>(S)) {
46 if (UnOp->getOpcode() == UO_AddrOf)
47 return isAccessForVar(UnOp->getSubExpr(), Var);
48 } else if (const auto *LE = dyn_cast<LambdaExpr>(S)) {
49 // Treat lambda capture by reference as a form of taking a reference.
50 return capturesByRef(LE->getLambdaClass(), Var);
51 } else if (const auto *ILE = dyn_cast<InitListExpr>(S)) {
52 return llvm::any_of(ILE->inits(), [Var](const Expr *ChildE) {
53 // If the child expression is a reference to Var, this means that it's
54 // used as an initializer of a reference-typed field. Otherwise
55 // it would have been surrounded with an implicit lvalue-to-rvalue cast.
56 return isAccessForVar(ChildE, Var);
57 });
58 }
59
60 return false;
61 }
62
63 /// Return whether \p Var has a pointer or reference in \p S.
hasPtrOrReferenceInStmt(const Stmt * S,const VarDecl * Var)64 static bool hasPtrOrReferenceInStmt(const Stmt *S, const VarDecl *Var) {
65 if (isPtrOrReferenceForVar(S, Var))
66 return true;
67
68 for (const Stmt *Child : S->children()) {
69 if (!Child)
70 continue;
71
72 if (hasPtrOrReferenceInStmt(Child, Var))
73 return true;
74 }
75
76 return false;
77 }
78
refersToEnclosingLambdaCaptureByRef(const Decl * Func,const VarDecl * Var)79 static bool refersToEnclosingLambdaCaptureByRef(const Decl *Func,
80 const VarDecl *Var) {
81 const auto *MD = dyn_cast<CXXMethodDecl>(Func);
82 if (!MD)
83 return false;
84
85 const CXXRecordDecl *RD = MD->getParent();
86 if (!RD->isLambda())
87 return false;
88
89 return capturesByRef(RD, Var);
90 }
91
hasPtrOrReferenceInFunc(const Decl * Func,const VarDecl * Var)92 bool hasPtrOrReferenceInFunc(const Decl *Func, const VarDecl *Var) {
93 return hasPtrOrReferenceInStmt(Func->getBody(), Var) ||
94 refersToEnclosingLambdaCaptureByRef(Func, Var);
95 }
96
97 } // namespace clang::tidy::utils
98