1 //===--- MagicNumbersCheck.cpp - clang-tidy-------------------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // A checker for magic numbers: integer or floating point literals embedded
11 // in the code, outside the definition of a constant or an enumeration.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "MagicNumbersCheck.h"
16 #include "../utils/OptionsUtils.h"
17 #include "clang/AST/ASTContext.h"
18 #include "clang/ASTMatchers/ASTMatchFinder.h"
19 #include "llvm/ADT/STLExtras.h"
20 #include <algorithm>
21 
22 using namespace clang::ast_matchers;
23 using namespace clang::ast_type_traits;
24 
25 namespace {
26 
27 bool isUsedToInitializeAConstant(const MatchFinder::MatchResult &Result,
28                                  const DynTypedNode &Node) {
29 
30   const auto *AsDecl = Node.get<clang::DeclaratorDecl>();
31   if (AsDecl) {
32     if (AsDecl->getType().isConstQualified())
33       return true;
34 
35     return AsDecl->isImplicit();
36   }
37 
38   if (Node.get<clang::EnumConstantDecl>() != nullptr)
39     return true;
40 
41   return llvm::any_of(Result.Context->getParents(Node),
42                       [&Result](const DynTypedNode &Parent) {
43                         return isUsedToInitializeAConstant(Result, Parent);
44                       });
45 }
46 
47 } // namespace
48 
49 namespace clang {
50 namespace tidy {
51 namespace readability {
52 
53 const char DefaultIgnoredIntegerValues[] = "1;2;3;4;";
54 const char DefaultIgnoredFloatingPointValues[] = "1.0;100.0;";
55 
56 MagicNumbersCheck::MagicNumbersCheck(StringRef Name, ClangTidyContext *Context)
57     : ClangTidyCheck(Name, Context),
58       IgnoreAllFloatingPointValues(
59           Options.get("IgnoreAllFloatingPointValues", false)),
60       IgnorePowersOf2IntegerValues(
61           Options.get("IgnorePowersOf2IntegerValues", false)) {
62   // Process the set of ignored integer values.
63   const std::vector<std::string> IgnoredIntegerValuesInput =
64       utils::options::parseStringList(
65           Options.get("IgnoredIntegerValues", DefaultIgnoredIntegerValues));
66   IgnoredIntegerValues.resize(IgnoredIntegerValuesInput.size());
67   llvm::transform(IgnoredIntegerValuesInput, IgnoredIntegerValues.begin(),
68                   [](const std::string &Value) { return std::stoll(Value); });
69   llvm::sort(IgnoredIntegerValues);
70 
71   if (!IgnoreAllFloatingPointValues) {
72     // Process the set of ignored floating point values.
73     const std::vector<std::string> IgnoredFloatingPointValuesInput =
74         utils::options::parseStringList(Options.get(
75             "IgnoredFloatingPointValues", DefaultIgnoredFloatingPointValues));
76     IgnoredFloatingPointValues.reserve(IgnoredFloatingPointValuesInput.size());
77     IgnoredDoublePointValues.reserve(IgnoredFloatingPointValuesInput.size());
78     for (const auto &InputValue : IgnoredFloatingPointValuesInput) {
79       llvm::APFloat FloatValue(llvm::APFloat::IEEEsingle());
80       FloatValue.convertFromString(InputValue, DefaultRoundingMode);
81       IgnoredFloatingPointValues.push_back(FloatValue.convertToFloat());
82 
83       llvm::APFloat DoubleValue(llvm::APFloat::IEEEdouble());
84       DoubleValue.convertFromString(InputValue, DefaultRoundingMode);
85       IgnoredDoublePointValues.push_back(DoubleValue.convertToDouble());
86     }
87     llvm::sort(IgnoredFloatingPointValues.begin(),
88                IgnoredFloatingPointValues.end());
89     llvm::sort(IgnoredDoublePointValues.begin(),
90                IgnoredDoublePointValues.end());
91   }
92 }
93 
94 void MagicNumbersCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
95   Options.store(Opts, "IgnoredIntegerValues", DefaultIgnoredIntegerValues);
96   Options.store(Opts, "IgnoredFloatingPointValues",
97                 DefaultIgnoredFloatingPointValues);
98 }
99 
100 void MagicNumbersCheck::registerMatchers(MatchFinder *Finder) {
101   Finder->addMatcher(integerLiteral().bind("integer"), this);
102   if (!IgnoreAllFloatingPointValues)
103     Finder->addMatcher(floatLiteral().bind("float"), this);
104 }
105 
106 void MagicNumbersCheck::check(const MatchFinder::MatchResult &Result) {
107   checkBoundMatch<IntegerLiteral>(Result, "integer");
108   checkBoundMatch<FloatingLiteral>(Result, "float");
109 }
110 
111 bool MagicNumbersCheck::isConstant(const MatchFinder::MatchResult &Result,
112                                    const Expr &ExprResult) const {
113   return llvm::any_of(
114       Result.Context->getParents(ExprResult),
115       [&Result](const DynTypedNode &Parent) {
116         return isUsedToInitializeAConstant(Result, Parent) ||
117                // Ignore this instance, because this match reports the location
118                // where the template is defined, not where it is instantiated.
119                Parent.get<SubstNonTypeTemplateParmExpr>();
120       });
121 }
122 
123 bool MagicNumbersCheck::isIgnoredValue(const IntegerLiteral *Literal) const {
124   const llvm::APInt IntValue = Literal->getValue();
125   const int64_t Value = IntValue.getZExtValue();
126   if (Value == 0)
127     return true;
128 
129   if (IgnorePowersOf2IntegerValues && IntValue.isPowerOf2())
130     return true;
131 
132   return std::binary_search(IgnoredIntegerValues.begin(),
133                             IgnoredIntegerValues.end(), Value);
134 }
135 
136 bool MagicNumbersCheck::isIgnoredValue(const FloatingLiteral *Literal) const {
137   const llvm::APFloat FloatValue = Literal->getValue();
138   if (FloatValue.isZero())
139     return true;
140 
141   if (&FloatValue.getSemantics() == &llvm::APFloat::IEEEsingle()) {
142     const float Value = FloatValue.convertToFloat();
143     return std::binary_search(IgnoredFloatingPointValues.begin(),
144                               IgnoredFloatingPointValues.end(), Value);
145   }
146 
147   if (&FloatValue.getSemantics() == &llvm::APFloat::IEEEdouble()) {
148     const double Value = FloatValue.convertToDouble();
149     return std::binary_search(IgnoredDoublePointValues.begin(),
150                               IgnoredDoublePointValues.end(), Value);
151   }
152 
153   return false;
154 }
155 
156 bool MagicNumbersCheck::isSyntheticValue(const SourceManager *SourceManager,
157                                          const IntegerLiteral *Literal) const {
158   const std::pair<FileID, unsigned> FileOffset =
159       SourceManager->getDecomposedLoc(Literal->getLocation());
160   if (FileOffset.first.isInvalid())
161     return false;
162 
163   const StringRef BufferIdentifier =
164       SourceManager->getBuffer(FileOffset.first)->getBufferIdentifier();
165 
166   return BufferIdentifier.empty();
167 }
168 
169 } // namespace readability
170 } // namespace tidy
171 } // namespace clang
172