1 //===--- SemaFixItUtils.cpp - Sema FixIts ---------------------------------===//
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 //  This file defines helper classes for generation of Sema FixItHints.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "clang/AST/ASTContext.h"
14 #include "clang/AST/ExprCXX.h"
15 #include "clang/AST/ExprObjC.h"
16 #include "clang/Lex/Preprocessor.h"
17 #include "clang/Sema/Sema.h"
18 #include "clang/Sema/SemaFixItUtils.h"
19 
20 using namespace clang;
21 
22 bool ConversionFixItGenerator::compareTypesSimple(CanQualType From,
23                                                   CanQualType To,
24                                                   Sema &S,
25                                                   SourceLocation Loc,
26                                                   ExprValueKind FromVK) {
27   if (!To.isAtLeastAsQualifiedAs(From))
28     return false;
29 
30   From = From.getNonReferenceType();
31   To = To.getNonReferenceType();
32 
33   // If both are pointer types, work with the pointee types.
34   if (isa<PointerType>(From) && isa<PointerType>(To)) {
35     From = S.Context.getCanonicalType(
36         (cast<PointerType>(From))->getPointeeType());
37     To = S.Context.getCanonicalType(
38         (cast<PointerType>(To))->getPointeeType());
39   }
40 
41   const CanQualType FromUnq = From.getUnqualifiedType();
42   const CanQualType ToUnq = To.getUnqualifiedType();
43 
44   if ((FromUnq == ToUnq || (S.IsDerivedFrom(Loc, FromUnq, ToUnq)) ) &&
45       To.isAtLeastAsQualifiedAs(From))
46     return true;
47   return false;
48 }
49 
50 bool ConversionFixItGenerator::tryToFixConversion(const Expr *FullExpr,
51                                                   const QualType FromTy,
52                                                   const QualType ToTy,
53                                                   Sema &S) {
54   if (!FullExpr)
55     return false;
56 
57   const CanQualType FromQTy = S.Context.getCanonicalType(FromTy);
58   const CanQualType ToQTy = S.Context.getCanonicalType(ToTy);
59   const SourceLocation Begin = FullExpr->getSourceRange().getBegin();
60   const SourceLocation End = S.getLocForEndOfToken(FullExpr->getSourceRange()
61                                                    .getEnd());
62 
63   // Strip the implicit casts - those are implied by the compiler, not the
64   // original source code.
65   const Expr* Expr = FullExpr->IgnoreImpCasts();
66 
67   bool NeedParen = true;
68   if (isa<ArraySubscriptExpr>(Expr) ||
69       isa<CallExpr>(Expr) ||
70       isa<DeclRefExpr>(Expr) ||
71       isa<CastExpr>(Expr) ||
72       isa<CXXNewExpr>(Expr) ||
73       isa<CXXConstructExpr>(Expr) ||
74       isa<CXXDeleteExpr>(Expr) ||
75       isa<CXXNoexceptExpr>(Expr) ||
76       isa<CXXPseudoDestructorExpr>(Expr) ||
77       isa<CXXScalarValueInitExpr>(Expr) ||
78       isa<CXXThisExpr>(Expr) ||
79       isa<CXXTypeidExpr>(Expr) ||
80       isa<CXXUnresolvedConstructExpr>(Expr) ||
81       isa<ObjCMessageExpr>(Expr) ||
82       isa<ObjCPropertyRefExpr>(Expr) ||
83       isa<ObjCProtocolExpr>(Expr) ||
84       isa<MemberExpr>(Expr) ||
85       isa<ParenExpr>(FullExpr) ||
86       isa<ParenListExpr>(Expr) ||
87       isa<SizeOfPackExpr>(Expr) ||
88       isa<UnaryOperator>(Expr))
89     NeedParen = false;
90 
91   // Check if the argument needs to be dereferenced:
92   //   (type * -> type) or (type * -> type &).
93   if (const PointerType *FromPtrTy = dyn_cast<PointerType>(FromQTy)) {
94     OverloadFixItKind FixKind = OFIK_Dereference;
95 
96     bool CanConvert = CompareTypes(
97       S.Context.getCanonicalType(FromPtrTy->getPointeeType()), ToQTy,
98                                  S, Begin, VK_LValue);
99     if (CanConvert) {
100       // Do not suggest dereferencing a Null pointer.
101       if (Expr->IgnoreParenCasts()->
102           isNullPointerConstant(S.Context, Expr::NPC_ValueDependentIsNotNull))
103         return false;
104 
105       if (const UnaryOperator *UO = dyn_cast<UnaryOperator>(Expr)) {
106         if (UO->getOpcode() == UO_AddrOf) {
107           FixKind = OFIK_RemoveTakeAddress;
108           Hints.push_back(FixItHint::CreateRemoval(
109                             CharSourceRange::getTokenRange(Begin, Begin)));
110         }
111       } else if (NeedParen) {
112         Hints.push_back(FixItHint::CreateInsertion(Begin, "*("));
113         Hints.push_back(FixItHint::CreateInsertion(End, ")"));
114       } else {
115         Hints.push_back(FixItHint::CreateInsertion(Begin, "*"));
116       }
117 
118       NumConversionsFixed++;
119       if (NumConversionsFixed == 1)
120         Kind = FixKind;
121       return true;
122     }
123   }
124 
125   // Check if the pointer to the argument needs to be passed:
126   //   (type -> type *) or (type & -> type *).
127   if (const auto *ToPtrTy = dyn_cast<PointerType>(ToQTy)) {
128     bool CanConvert = false;
129     OverloadFixItKind FixKind = OFIK_TakeAddress;
130 
131     // Only suggest taking address of L-values.
132     if (!Expr->isLValue() || Expr->getObjectKind() != OK_Ordinary)
133       return false;
134 
135     // Do no take address of const pointer to get void*
136     if (isa<PointerType>(FromQTy) && ToPtrTy->isVoidPointerType())
137       return false;
138 
139     CanConvert = CompareTypes(S.Context.getPointerType(FromQTy), ToQTy, S,
140                               Begin, VK_PRValue);
141     if (CanConvert) {
142 
143       if (const UnaryOperator *UO = dyn_cast<UnaryOperator>(Expr)) {
144         if (UO->getOpcode() == UO_Deref) {
145           FixKind = OFIK_RemoveDereference;
146           Hints.push_back(FixItHint::CreateRemoval(
147                             CharSourceRange::getTokenRange(Begin, Begin)));
148         }
149       } else if (NeedParen) {
150         Hints.push_back(FixItHint::CreateInsertion(Begin, "&("));
151         Hints.push_back(FixItHint::CreateInsertion(End, ")"));
152       } else {
153         Hints.push_back(FixItHint::CreateInsertion(Begin, "&"));
154       }
155 
156       NumConversionsFixed++;
157       if (NumConversionsFixed == 1)
158         Kind = FixKind;
159       return true;
160     }
161   }
162 
163   return false;
164 }
165 
166 static bool isMacroDefined(const Sema &S, SourceLocation Loc, StringRef Name) {
167   return (bool)S.PP.getMacroDefinitionAtLoc(&S.getASTContext().Idents.get(Name),
168                                             Loc);
169 }
170 
171 static std::string getScalarZeroExpressionForType(
172     const Type &T, SourceLocation Loc, const Sema &S) {
173   assert(T.isScalarType() && "use scalar types only");
174   // Suggest "0" for non-enumeration scalar types, unless we can find a
175   // better initializer.
176   if (T.isEnumeralType())
177     return std::string();
178   if ((T.isObjCObjectPointerType() || T.isBlockPointerType()) &&
179       isMacroDefined(S, Loc, "nil"))
180     return "nil";
181   if (T.isRealFloatingType())
182     return "0.0";
183   if (T.isBooleanType() &&
184       (S.LangOpts.CPlusPlus || isMacroDefined(S, Loc, "false")))
185     return "false";
186   if (T.isPointerType() || T.isMemberPointerType()) {
187     if (S.LangOpts.CPlusPlus11)
188       return "nullptr";
189     if (isMacroDefined(S, Loc, "NULL"))
190       return "NULL";
191   }
192   if (T.isCharType())
193     return "'\\0'";
194   if (T.isWideCharType())
195     return "L'\\0'";
196   if (T.isChar16Type())
197     return "u'\\0'";
198   if (T.isChar32Type())
199     return "U'\\0'";
200   return "0";
201 }
202 
203 std::string
204 Sema::getFixItZeroInitializerForType(QualType T, SourceLocation Loc) const {
205   if (T->isScalarType()) {
206     std::string s = getScalarZeroExpressionForType(*T, Loc, *this);
207     if (!s.empty())
208       s = " = " + s;
209     return s;
210   }
211 
212   const CXXRecordDecl *RD = T->getAsCXXRecordDecl();
213   if (!RD || !RD->hasDefinition())
214     return std::string();
215   if (LangOpts.CPlusPlus11 && !RD->hasUserProvidedDefaultConstructor())
216     return "{}";
217   if (RD->isAggregate())
218     return " = {}";
219   return std::string();
220 }
221 
222 std::string
223 Sema::getFixItZeroLiteralForType(QualType T, SourceLocation Loc) const {
224   return getScalarZeroExpressionForType(*T, Loc, *this);
225 }
226