1 //===--- StringIntegerAssignmentCheck.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 "StringIntegerAssignmentCheck.h"
10 #include "clang/AST/ASTContext.h"
11 #include "clang/ASTMatchers/ASTMatchFinder.h"
12 #include "clang/Lex/Lexer.h"
13
14 using namespace clang::ast_matchers;
15
16 namespace clang::tidy::bugprone {
17
registerMatchers(MatchFinder * Finder)18 void StringIntegerAssignmentCheck::registerMatchers(MatchFinder *Finder) {
19 Finder->addMatcher(
20 cxxOperatorCallExpr(
21 hasAnyOverloadedOperatorName("=", "+="),
22 callee(cxxMethodDecl(ofClass(classTemplateSpecializationDecl(
23 hasName("::std::basic_string"),
24 hasTemplateArgument(0, refersToType(hasCanonicalType(
25 qualType().bind("type")))))))),
26 hasArgument(
27 1,
28 ignoringImpCasts(
29 expr(hasType(isInteger()), unless(hasType(isAnyCharacter())),
30 // Ignore calls to tolower/toupper (see PR27723).
31 unless(callExpr(callee(functionDecl(
32 hasAnyName("tolower", "std::tolower", "toupper",
33 "std::toupper"))))),
34 // Do not warn if assigning e.g. `CodePoint` to
35 // `basic_string<CodePoint>`
36 unless(hasType(qualType(
37 hasCanonicalType(equalsBoundNode("type"))))))
38 .bind("expr"))),
39 unless(isInTemplateInstantiation())),
40 this);
41 }
42
43 class CharExpressionDetector {
44 public:
CharExpressionDetector(QualType CharType,const ASTContext & Ctx)45 CharExpressionDetector(QualType CharType, const ASTContext &Ctx)
46 : CharType(CharType), Ctx(Ctx) {}
47
isLikelyCharExpression(const Expr * E) const48 bool isLikelyCharExpression(const Expr *E) const {
49 if (isCharTyped(E))
50 return true;
51
52 if (const auto *BinOp = dyn_cast<BinaryOperator>(E)) {
53 const auto *LHS = BinOp->getLHS()->IgnoreParenImpCasts();
54 const auto *RHS = BinOp->getRHS()->IgnoreParenImpCasts();
55 // Handle both directions, e.g. `'a' + (i % 26)` and `(i % 26) + 'a'`.
56 if (BinOp->isAdditiveOp() || BinOp->isBitwiseOp())
57 return handleBinaryOp(BinOp->getOpcode(), LHS, RHS) ||
58 handleBinaryOp(BinOp->getOpcode(), RHS, LHS);
59 // Except in the case of '%'.
60 if (BinOp->getOpcode() == BO_Rem)
61 return handleBinaryOp(BinOp->getOpcode(), LHS, RHS);
62 return false;
63 }
64
65 // Ternary where at least one branch is a likely char expression, e.g.
66 // i < 265 ? i : ' '
67 if (const auto *CondOp = dyn_cast<AbstractConditionalOperator>(E))
68 return isLikelyCharExpression(
69 CondOp->getFalseExpr()->IgnoreParenImpCasts()) ||
70 isLikelyCharExpression(
71 CondOp->getTrueExpr()->IgnoreParenImpCasts());
72 return false;
73 }
74
75 private:
handleBinaryOp(clang::BinaryOperatorKind Opcode,const Expr * const LHS,const Expr * const RHS) const76 bool handleBinaryOp(clang::BinaryOperatorKind Opcode, const Expr *const LHS,
77 const Expr *const RHS) const {
78 // <char_expr> <op> <char_expr> (c++ integer promotion rules make this an
79 // int), e.g.
80 // 'a' + c
81 if (isCharTyped(LHS) && isCharTyped(RHS))
82 return true;
83
84 // <expr> & <char_valued_constant> or <expr> % <char_valued_constant>, e.g.
85 // i & 0xff
86 if ((Opcode == BO_And || Opcode == BO_Rem) && isCharValuedConstant(RHS))
87 return true;
88
89 // <char_expr> | <char_valued_constant>, e.g.
90 // c | 0x80
91 if (Opcode == BO_Or && isCharTyped(LHS) && isCharValuedConstant(RHS))
92 return true;
93
94 // <char_constant> + <likely_char_expr>, e.g.
95 // 'a' + (i % 26)
96 if (Opcode == BO_Add)
97 return isCharConstant(LHS) && isLikelyCharExpression(RHS);
98
99 return false;
100 }
101
102 // Returns true if `E` is an character constant.
isCharConstant(const Expr * E) const103 bool isCharConstant(const Expr *E) const {
104 return isCharTyped(E) && isCharValuedConstant(E);
105 };
106
107 // Returns true if `E` is an integer constant which fits in `CharType`.
isCharValuedConstant(const Expr * E) const108 bool isCharValuedConstant(const Expr *E) const {
109 if (E->isInstantiationDependent())
110 return false;
111 Expr::EvalResult EvalResult;
112 if (!E->EvaluateAsInt(EvalResult, Ctx, Expr::SE_AllowSideEffects))
113 return false;
114 return EvalResult.Val.getInt().getActiveBits() <= Ctx.getTypeSize(CharType);
115 };
116
117 // Returns true if `E` has the right character type.
isCharTyped(const Expr * E) const118 bool isCharTyped(const Expr *E) const {
119 return E->getType().getCanonicalType().getTypePtr() ==
120 CharType.getTypePtr();
121 };
122
123 const QualType CharType;
124 const ASTContext &Ctx;
125 };
126
check(const MatchFinder::MatchResult & Result)127 void StringIntegerAssignmentCheck::check(
128 const MatchFinder::MatchResult &Result) {
129 const auto *Argument = Result.Nodes.getNodeAs<Expr>("expr");
130 const auto CharType =
131 Result.Nodes.getNodeAs<QualType>("type")->getCanonicalType();
132 SourceLocation Loc = Argument->getBeginLoc();
133
134 // Try to detect a few common expressions to reduce false positives.
135 if (CharExpressionDetector(CharType, *Result.Context)
136 .isLikelyCharExpression(Argument))
137 return;
138
139 auto Diag =
140 diag(Loc, "an integer is interpreted as a character code when assigning "
141 "it to a string; if this is intended, cast the integer to the "
142 "appropriate character type; if you want a string "
143 "representation, use the appropriate conversion facility");
144
145 if (Loc.isMacroID())
146 return;
147
148 bool IsWideCharType = CharType->isWideCharType();
149 if (!CharType->isCharType() && !IsWideCharType)
150 return;
151 bool IsOneDigit = false;
152 bool IsLiteral = false;
153 if (const auto *Literal = dyn_cast<IntegerLiteral>(Argument)) {
154 IsOneDigit = Literal->getValue().getLimitedValue() < 10;
155 IsLiteral = true;
156 }
157
158 SourceLocation EndLoc = Lexer::getLocForEndOfToken(
159 Argument->getEndLoc(), 0, *Result.SourceManager, getLangOpts());
160 if (IsOneDigit) {
161 Diag << FixItHint::CreateInsertion(Loc, IsWideCharType ? "L'" : "'")
162 << FixItHint::CreateInsertion(EndLoc, "'");
163 return;
164 }
165 if (IsLiteral) {
166 Diag << FixItHint::CreateInsertion(Loc, IsWideCharType ? "L\"" : "\"")
167 << FixItHint::CreateInsertion(EndLoc, "\"");
168 return;
169 }
170
171 if (getLangOpts().CPlusPlus11) {
172 Diag << FixItHint::CreateInsertion(Loc, IsWideCharType ? "std::to_wstring("
173 : "std::to_string(")
174 << FixItHint::CreateInsertion(EndLoc, ")");
175 }
176 }
177
178 } // namespace clang::tidy::bugprone
179