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