clang-tools  14.0.0git
MagicNumbersCheck.cpp
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1 //===--- MagicNumbersCheck.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 // A checker for magic numbers: integer or floating point literals embedded
10 // in the code, outside the definition of a constant or an enumeration.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "MagicNumbersCheck.h"
15 #include "../utils/OptionsUtils.h"
16 #include "clang/AST/ASTContext.h"
17 #include "clang/ASTMatchers/ASTMatchFinder.h"
18 #include "llvm/ADT/STLExtras.h"
19 #include <algorithm>
20 
21 using namespace clang::ast_matchers;
22 
23 namespace clang {
24 
25 static bool isUsedToInitializeAConstant(const MatchFinder::MatchResult &Result,
26  const DynTypedNode &Node) {
27 
28  const auto *AsDecl = Node.get<DeclaratorDecl>();
29  if (AsDecl) {
30  if (AsDecl->getType().isConstQualified())
31  return true;
32 
33  return AsDecl->isImplicit();
34  }
35 
36  if (Node.get<EnumConstantDecl>())
37  return true;
38 
39  return llvm::any_of(Result.Context->getParents(Node),
40  [&Result](const DynTypedNode &Parent) {
41  return isUsedToInitializeAConstant(Result, Parent);
42  });
43 }
44 
45 static bool isUsedToDefineABitField(const MatchFinder::MatchResult &Result,
46  const DynTypedNode &Node) {
47  const auto *AsFieldDecl = Node.get<FieldDecl>();
48  if (AsFieldDecl && AsFieldDecl->isBitField())
49  return true;
50 
51  return llvm::any_of(Result.Context->getParents(Node),
52  [&Result](const DynTypedNode &Parent) {
53  return isUsedToDefineABitField(Result, Parent);
54  });
55 }
56 
57 namespace tidy {
58 namespace readability {
59 
60 const char DefaultIgnoredIntegerValues[] = "1;2;3;4;";
61 const char DefaultIgnoredFloatingPointValues[] = "1.0;100.0;";
62 
63 MagicNumbersCheck::MagicNumbersCheck(StringRef Name, ClangTidyContext *Context)
64  : ClangTidyCheck(Name, Context),
65  IgnoreAllFloatingPointValues(
66  Options.get("IgnoreAllFloatingPointValues", false)),
67  IgnoreBitFieldsWidths(Options.get("IgnoreBitFieldsWidths", true)),
68  IgnorePowersOf2IntegerValues(
69  Options.get("IgnorePowersOf2IntegerValues", false)),
70  RawIgnoredIntegerValues(
71  Options.get("IgnoredIntegerValues", DefaultIgnoredIntegerValues)),
72  RawIgnoredFloatingPointValues(Options.get(
73  "IgnoredFloatingPointValues", DefaultIgnoredFloatingPointValues)) {
74  // Process the set of ignored integer values.
75  const std::vector<std::string> IgnoredIntegerValuesInput =
76  utils::options::parseStringList(RawIgnoredIntegerValues);
77  IgnoredIntegerValues.resize(IgnoredIntegerValuesInput.size());
78  llvm::transform(IgnoredIntegerValuesInput, IgnoredIntegerValues.begin(),
79  [](const std::string &Value) { return std::stoll(Value); });
80  llvm::sort(IgnoredIntegerValues);
81 
82  if (!IgnoreAllFloatingPointValues) {
83  // Process the set of ignored floating point values.
84  const std::vector<std::string> IgnoredFloatingPointValuesInput =
85  utils::options::parseStringList(RawIgnoredFloatingPointValues);
86  IgnoredFloatingPointValues.reserve(IgnoredFloatingPointValuesInput.size());
87  IgnoredDoublePointValues.reserve(IgnoredFloatingPointValuesInput.size());
88  for (const auto &InputValue : IgnoredFloatingPointValuesInput) {
89  llvm::APFloat FloatValue(llvm::APFloat::IEEEsingle());
90  auto StatusOrErr =
91  FloatValue.convertFromString(InputValue, DefaultRoundingMode);
92  assert(StatusOrErr && "Invalid floating point representation");
93  consumeError(StatusOrErr.takeError());
94  IgnoredFloatingPointValues.push_back(FloatValue.convertToFloat());
95 
96  llvm::APFloat DoubleValue(llvm::APFloat::IEEEdouble());
97  StatusOrErr =
98  DoubleValue.convertFromString(InputValue, DefaultRoundingMode);
99  assert(StatusOrErr && "Invalid floating point representation");
100  consumeError(StatusOrErr.takeError());
101  IgnoredDoublePointValues.push_back(DoubleValue.convertToDouble());
102  }
103  llvm::sort(IgnoredFloatingPointValues.begin(),
104  IgnoredFloatingPointValues.end());
105  llvm::sort(IgnoredDoublePointValues.begin(),
106  IgnoredDoublePointValues.end());
107  }
108 }
109 
111  Options.store(Opts, "IgnoreAllFloatingPointValues",
112  IgnoreAllFloatingPointValues);
113  Options.store(Opts, "IgnoreBitFieldsWidths", IgnoreBitFieldsWidths);
114  Options.store(Opts, "IgnorePowersOf2IntegerValues",
115  IgnorePowersOf2IntegerValues);
116  Options.store(Opts, "IgnoredIntegerValues", RawIgnoredIntegerValues);
117  Options.store(Opts, "IgnoredFloatingPointValues",
118  RawIgnoredFloatingPointValues);
119 }
120 
121 void MagicNumbersCheck::registerMatchers(MatchFinder *Finder) {
122  Finder->addMatcher(integerLiteral().bind("integer"), this);
123  if (!IgnoreAllFloatingPointValues)
124  Finder->addMatcher(floatLiteral().bind("float"), this);
125 }
126 
127 void MagicNumbersCheck::check(const MatchFinder::MatchResult &Result) {
128 
129  TraversalKindScope RAII(*Result.Context, TK_AsIs);
130 
131  checkBoundMatch<IntegerLiteral>(Result, "integer");
132  checkBoundMatch<FloatingLiteral>(Result, "float");
133 }
134 
135 bool MagicNumbersCheck::isConstant(const MatchFinder::MatchResult &Result,
136  const Expr &ExprResult) const {
137  return llvm::any_of(
138  Result.Context->getParents(ExprResult),
139  [&Result](const DynTypedNode &Parent) {
140  if (isUsedToInitializeAConstant(Result, Parent))
141  return true;
142 
143  // Ignore this instance, because this matches an
144  // expanded class enumeration value.
145  if (Parent.get<CStyleCastExpr>() &&
146  llvm::any_of(
147  Result.Context->getParents(Parent),
148  [](const DynTypedNode &GrandParent) {
149  return GrandParent.get<SubstNonTypeTemplateParmExpr>() !=
150  nullptr;
151  }))
152  return true;
153 
154  // Ignore this instance, because this match reports the
155  // location where the template is defined, not where it
156  // is instantiated.
157  if (Parent.get<SubstNonTypeTemplateParmExpr>())
158  return true;
159 
160  // Don't warn on string user defined literals:
161  // std::string s = "Hello World"s;
162  if (const auto *UDL = Parent.get<UserDefinedLiteral>())
163  if (UDL->getLiteralOperatorKind() == UserDefinedLiteral::LOK_String)
164  return true;
165 
166  return false;
167  });
168 }
169 
170 bool MagicNumbersCheck::isIgnoredValue(const IntegerLiteral *Literal) const {
171  const llvm::APInt IntValue = Literal->getValue();
172  const int64_t Value = IntValue.getZExtValue();
173  if (Value == 0)
174  return true;
175 
176  if (IgnorePowersOf2IntegerValues && IntValue.isPowerOf2())
177  return true;
178 
179  return std::binary_search(IgnoredIntegerValues.begin(),
180  IgnoredIntegerValues.end(), Value);
181 }
182 
183 bool MagicNumbersCheck::isIgnoredValue(const FloatingLiteral *Literal) const {
184  const llvm::APFloat FloatValue = Literal->getValue();
185  if (FloatValue.isZero())
186  return true;
187 
188  if (&FloatValue.getSemantics() == &llvm::APFloat::IEEEsingle()) {
189  const float Value = FloatValue.convertToFloat();
190  return std::binary_search(IgnoredFloatingPointValues.begin(),
191  IgnoredFloatingPointValues.end(), Value);
192  }
193 
194  if (&FloatValue.getSemantics() == &llvm::APFloat::IEEEdouble()) {
195  const double Value = FloatValue.convertToDouble();
196  return std::binary_search(IgnoredDoublePointValues.begin(),
197  IgnoredDoublePointValues.end(), Value);
198  }
199 
200  return false;
201 }
202 
203 bool MagicNumbersCheck::isSyntheticValue(const SourceManager *SourceManager,
204  const IntegerLiteral *Literal) const {
205  const std::pair<FileID, unsigned> FileOffset =
206  SourceManager->getDecomposedLoc(Literal->getLocation());
207  if (FileOffset.first.isInvalid())
208  return false;
209 
210  const StringRef BufferIdentifier =
211  SourceManager->getBufferOrFake(FileOffset.first).getBufferIdentifier();
212 
213  return BufferIdentifier.empty();
214 }
215 
216 bool MagicNumbersCheck::isBitFieldWidth(
217  const clang::ast_matchers::MatchFinder::MatchResult &Result,
218  const IntegerLiteral &Literal) const {
219  return IgnoreBitFieldsWidths &&
220  llvm::any_of(Result.Context->getParents(Literal),
221  [&Result](const DynTypedNode &Parent) {
222  return isUsedToDefineABitField(Result, Parent);
223  });
224 }
225 
226 } // namespace readability
227 } // namespace tidy
228 } // namespace clang
clang::tidy::readability::MagicNumbersCheck::check
void check(const ast_matchers::MatchFinder::MatchResult &Result) override
ClangTidyChecks that register ASTMatchers should do the actual work in here.
Definition: MagicNumbersCheck.cpp:127
clang::isUsedToInitializeAConstant
static bool isUsedToInitializeAConstant(const MatchFinder::MatchResult &Result, const DynTypedNode &Node)
Definition: MagicNumbersCheck.cpp:25
clang::tidy::ClangTidyOptions::OptionMap
llvm::StringMap< ClangTidyValue > OptionMap
Definition: ClangTidyOptions.h:115
clang::tidy::readability::DefaultIgnoredFloatingPointValues
const char DefaultIgnoredFloatingPointValues[]
Definition: MagicNumbersCheck.cpp:61
clang::tidy::readability::DefaultIgnoredIntegerValues
const char DefaultIgnoredIntegerValues[]
Definition: MagicNumbersCheck.cpp:60
clang::tidy::ClangTidyCheck
Base class for all clang-tidy checks.
Definition: ClangTidyCheck.h:54
clang::ast_matchers
Definition: AbseilMatcher.h:14
clang::isUsedToDefineABitField
static bool isUsedToDefineABitField(const MatchFinder::MatchResult &Result, const DynTypedNode &Node)
Definition: MagicNumbersCheck.cpp:45
clang::tidy::utils::options::parseStringList
std::vector< std::string > parseStringList(StringRef Option)
Parse a semicolon separated list of strings.
Definition: OptionsUtils.cpp:18
clang::tidy::readability::MagicNumbersCheck::storeOptions
void storeOptions(ClangTidyOptions::OptionMap &Opts) override
Should store all options supported by this check with their current values or default values for opti...
Definition: MagicNumbersCheck.cpp:110
clang::tidy::ClangTidyCheck::Options
OptionsView Options
Definition: ClangTidyCheck.h:416
clang::tidy::ClangTidyContext
Every ClangTidyCheck reports errors through a DiagnosticsEngine provided by this context.
Definition: ClangTidyDiagnosticConsumer.h:72
Name
static constexpr llvm::StringLiteral Name
Definition: UppercaseLiteralSuffixCheck.cpp:28
clang::tidy::readability::MagicNumbersCheck::registerMatchers
void registerMatchers(ast_matchers::MatchFinder *Finder) override
Override this to register AST matchers with Finder.
Definition: MagicNumbersCheck.cpp:121
Parent
const Node * Parent
Definition: ExtractFunction.cpp:152
clang
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//
Definition: ApplyReplacements.h:27
MagicNumbersCheck.h
clang::tidy::ClangTidyCheck::OptionsView::store
void store(ClangTidyOptions::OptionMap &Options, StringRef LocalName, StringRef Value) const
Stores an option with the check-local name LocalName with string value Value to Options.
Definition: ClangTidyCheck.cpp:120