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 {
15 namespace tidy {
16 namespace utils {
17
18 /// Return whether \p S is a reference to the declaration of \p Var.
isAccessForVar(const Stmt * S,const VarDecl * Var)19 static bool isAccessForVar(const Stmt *S, const VarDecl *Var) {
20 if (const auto *DRE = dyn_cast<DeclRefExpr>(S))
21 return DRE->getDecl() == Var;
22
23 return false;
24 }
25
capturesByRef(const CXXRecordDecl * RD,const VarDecl * Var)26 static bool capturesByRef(const CXXRecordDecl *RD, const VarDecl *Var) {
27 return llvm::any_of(RD->captures(), [Var](const LambdaCapture &C) {
28 return C.capturesVariable() && C.getCaptureKind() == LCK_ByRef &&
29 C.getCapturedVar() == Var;
30 });
31 }
32
33 /// Return whether \p Var has a pointer or reference in \p S.
isPtrOrReferenceForVar(const Stmt * S,const VarDecl * Var)34 static bool isPtrOrReferenceForVar(const Stmt *S, const VarDecl *Var) {
35 // Treat block capture by reference as a form of taking a reference.
36 if (Var->isEscapingByref())
37 return true;
38
39 if (const auto *DS = dyn_cast<DeclStmt>(S)) {
40 for (const Decl *D : DS->getDeclGroup()) {
41 if (const auto *LeftVar = dyn_cast<VarDecl>(D)) {
42 if (LeftVar->hasInit() && LeftVar->getType()->isReferenceType()) {
43 return isAccessForVar(LeftVar->getInit(), Var);
44 }
45 }
46 }
47 } else if (const auto *UnOp = dyn_cast<UnaryOperator>(S)) {
48 if (UnOp->getOpcode() == UO_AddrOf)
49 return isAccessForVar(UnOp->getSubExpr(), Var);
50 } else if (const auto *LE = dyn_cast<LambdaExpr>(S)) {
51 // Treat lambda capture by reference as a form of taking a reference.
52 return capturesByRef(LE->getLambdaClass(), Var);
53 } else if (const auto *ILE = dyn_cast<InitListExpr>(S)) {
54 return llvm::any_of(ILE->inits(), [Var](const Expr *ChildE) {
55 // If the child expression is a reference to Var, this means that it's
56 // used as an initializer of a reference-typed field. Otherwise
57 // it would have been surrounded with an implicit lvalue-to-rvalue cast.
58 return isAccessForVar(ChildE, Var);
59 });
60 }
61
62 return false;
63 }
64
65 /// Return whether \p Var has a pointer or reference in \p S.
hasPtrOrReferenceInStmt(const Stmt * S,const VarDecl * Var)66 static bool hasPtrOrReferenceInStmt(const Stmt *S, const VarDecl *Var) {
67 if (isPtrOrReferenceForVar(S, Var))
68 return true;
69
70 for (const Stmt *Child : S->children()) {
71 if (!Child)
72 continue;
73
74 if (hasPtrOrReferenceInStmt(Child, Var))
75 return true;
76 }
77
78 return false;
79 }
80
refersToEnclosingLambdaCaptureByRef(const Decl * Func,const VarDecl * Var)81 static bool refersToEnclosingLambdaCaptureByRef(const Decl *Func,
82 const VarDecl *Var) {
83 const auto *MD = dyn_cast<CXXMethodDecl>(Func);
84 if (!MD)
85 return false;
86
87 const CXXRecordDecl *RD = MD->getParent();
88 if (!RD->isLambda())
89 return false;
90
91 return capturesByRef(RD, Var);
92 }
93
hasPtrOrReferenceInFunc(const Decl * Func,const VarDecl * Var)94 bool hasPtrOrReferenceInFunc(const Decl *Func, const VarDecl *Var) {
95 return hasPtrOrReferenceInStmt(Func->getBody(), Var) ||
96 refersToEnclosingLambdaCaptureByRef(Func, Var);
97 }
98
99 } // namespace utils
100 } // namespace tidy
101 } // namespace clang
102