clang-tools  9.0.0
SuspiciousEnumUsageCheck.cpp
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1 //===--- SuspiciousEnumUsageCheck.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 
10 #include "clang/AST/ASTContext.h"
11 #include "clang/ASTMatchers/ASTMatchFinder.h"
12 #include <algorithm>
13 
14 using namespace clang::ast_matchers;
15 
16 namespace clang {
17 namespace tidy {
18 namespace bugprone {
19 
20 static const char DifferentEnumErrorMessage[] =
21  "enum values are from different enum types";
22 
23 static const char BitmaskErrorMessage[] =
24  "enum type seems like a bitmask (contains mostly "
25  "power-of-2 literals), but this literal is not a "
26  "power-of-2";
27 
28 static const char BitmaskVarErrorMessage[] =
29  "enum type seems like a bitmask (contains mostly "
30  "power-of-2 literals) but %plural{1:a literal is|:some literals are}0 not "
31  "power-of-2";
32 
33 static const char BitmaskNoteMessage[] = "used here as a bitmask";
34 
35 /// Stores a min and a max value which describe an interval.
36 struct ValueRange {
37  llvm::APSInt MinVal;
38  llvm::APSInt MaxVal;
39 
40  ValueRange(const EnumDecl *EnumDec) {
41  const auto MinMaxVal = std::minmax_element(
42  EnumDec->enumerator_begin(), EnumDec->enumerator_end(),
43  [](const EnumConstantDecl *E1, const EnumConstantDecl *E2) {
44  return llvm::APSInt::compareValues(E1->getInitVal(),
45  E2->getInitVal()) < 0;
46  });
47  MinVal = MinMaxVal.first->getInitVal();
48  MaxVal = MinMaxVal.second->getInitVal();
49  }
50 };
51 
52 /// Return the number of EnumConstantDecls in an EnumDecl.
53 static int enumLength(const EnumDecl *EnumDec) {
54  return std::distance(EnumDec->enumerator_begin(), EnumDec->enumerator_end());
55 }
56 
57 static bool hasDisjointValueRange(const EnumDecl *Enum1,
58  const EnumDecl *Enum2) {
59  ValueRange Range1(Enum1), Range2(Enum2);
60  return llvm::APSInt::compareValues(Range1.MaxVal, Range2.MinVal) < 0 ||
61  llvm::APSInt::compareValues(Range2.MaxVal, Range1.MinVal) < 0;
62 }
63 
64 static bool isNonPowerOf2NorNullLiteral(const EnumConstantDecl *EnumConst) {
65  llvm::APSInt Val = EnumConst->getInitVal();
66  if (Val.isPowerOf2() || !Val.getBoolValue())
67  return false;
68  const Expr *InitExpr = EnumConst->getInitExpr();
69  if (!InitExpr)
70  return true;
71  return isa<IntegerLiteral>(InitExpr->IgnoreImpCasts());
72 }
73 
74 static bool isMaxValAllBitSetLiteral(const EnumDecl *EnumDec) {
75  auto EnumConst = std::max_element(
76  EnumDec->enumerator_begin(), EnumDec->enumerator_end(),
77  [](const EnumConstantDecl *E1, const EnumConstantDecl *E2) {
78  return E1->getInitVal() < E2->getInitVal();
79  });
80 
81  if (const Expr *InitExpr = EnumConst->getInitExpr()) {
82  return EnumConst->getInitVal().countTrailingOnes() ==
83  EnumConst->getInitVal().getActiveBits() &&
84  isa<IntegerLiteral>(InitExpr->IgnoreImpCasts());
85  }
86  return false;
87 }
88 
89 static int countNonPowOfTwoLiteralNum(const EnumDecl *EnumDec) {
90  return std::count_if(
91  EnumDec->enumerator_begin(), EnumDec->enumerator_end(),
92  [](const EnumConstantDecl *E) { return isNonPowerOf2NorNullLiteral(E); });
93 }
94 
95 /// Check if there is one or two enumerators that are not a power of 2 and are
96 /// initialized by a literal in the enum type, and that the enumeration contains
97 /// enough elements to reasonably act as a bitmask. Exclude the case where the
98 /// last enumerator is the sum of the lesser values (and initialized by a
99 /// literal) or when it could contain consecutive values.
100 static bool isPossiblyBitMask(const EnumDecl *EnumDec) {
101  ValueRange VR(EnumDec);
102  int EnumLen = enumLength(EnumDec);
103  int NonPowOfTwoCounter = countNonPowOfTwoLiteralNum(EnumDec);
104  return NonPowOfTwoCounter >= 1 && NonPowOfTwoCounter <= 2 &&
105  NonPowOfTwoCounter < EnumLen / 2 &&
106  (VR.MaxVal - VR.MinVal != EnumLen - 1) &&
107  !(NonPowOfTwoCounter == 1 && isMaxValAllBitSetLiteral(EnumDec));
108 }
109 
110 SuspiciousEnumUsageCheck::SuspiciousEnumUsageCheck(StringRef Name,
111  ClangTidyContext *Context)
112  : ClangTidyCheck(Name, Context),
113  StrictMode(Options.getLocalOrGlobal("StrictMode", 0)) {}
114 
116  Options.store(Opts, "StrictMode", StrictMode);
117 }
118 
120  const auto enumExpr = [](StringRef RefName, StringRef DeclName) {
121  return expr(ignoringImpCasts(expr().bind(RefName)),
122  ignoringImpCasts(hasType(enumDecl().bind(DeclName))));
123  };
124 
125  Finder->addMatcher(
126  binaryOperator(hasOperatorName("|"), hasLHS(enumExpr("", "enumDecl")),
127  hasRHS(expr(enumExpr("", "otherEnumDecl"),
128  ignoringImpCasts(hasType(enumDecl(
129  unless(equalsBoundNode("enumDecl"))))))))
130  .bind("diffEnumOp"),
131  this);
132 
133  Finder->addMatcher(
134  binaryOperator(anyOf(hasOperatorName("+"), hasOperatorName("|")),
135  hasLHS(enumExpr("lhsExpr", "enumDecl")),
136  hasRHS(expr(enumExpr("rhsExpr", ""),
137  ignoringImpCasts(hasType(
138  enumDecl(equalsBoundNode("enumDecl"))))))),
139  this);
140 
141  Finder->addMatcher(
142  binaryOperator(anyOf(hasOperatorName("+"), hasOperatorName("|")),
143  hasEitherOperand(
144  expr(hasType(isInteger()), unless(enumExpr("", "")))),
145  hasEitherOperand(enumExpr("enumExpr", "enumDecl"))),
146  this);
147 
148  Finder->addMatcher(
149  binaryOperator(anyOf(hasOperatorName("|="), hasOperatorName("+=")),
150  hasRHS(enumExpr("enumExpr", "enumDecl"))),
151  this);
152 }
153 
154 void SuspiciousEnumUsageCheck::checkSuspiciousBitmaskUsage(
155  const Expr *NodeExpr, const EnumDecl *EnumDec) {
156  const auto *EnumExpr = dyn_cast<DeclRefExpr>(NodeExpr);
157  const auto *EnumConst =
158  EnumExpr ? dyn_cast<EnumConstantDecl>(EnumExpr->getDecl()) : nullptr;
159 
160  // Report the parameter if neccessary.
161  if (!EnumConst) {
162  diag(EnumDec->getInnerLocStart(), BitmaskVarErrorMessage)
163  << countNonPowOfTwoLiteralNum(EnumDec);
164  diag(EnumExpr->getExprLoc(), BitmaskNoteMessage, DiagnosticIDs::Note);
165  } else if (isNonPowerOf2NorNullLiteral(EnumConst)) {
166  diag(EnumConst->getSourceRange().getBegin(), BitmaskErrorMessage);
167  diag(EnumExpr->getExprLoc(), BitmaskNoteMessage, DiagnosticIDs::Note);
168  }
169 }
170 
171 void SuspiciousEnumUsageCheck::check(const MatchFinder::MatchResult &Result) {
172  // Case 1: The two enum values come from different types.
173  if (const auto *DiffEnumOp =
174  Result.Nodes.getNodeAs<BinaryOperator>("diffEnumOp")) {
175  const auto *EnumDec = Result.Nodes.getNodeAs<EnumDecl>("enumDecl");
176  const auto *OtherEnumDec =
177  Result.Nodes.getNodeAs<EnumDecl>("otherEnumDecl");
178  // Skip when one of the parameters is an empty enum. The
179  // hasDisjointValueRange function could not decide the values properly in
180  // case of an empty enum.
181  if (EnumDec->enumerator_begin() == EnumDec->enumerator_end() ||
182  OtherEnumDec->enumerator_begin() == OtherEnumDec->enumerator_end())
183  return;
184 
185  if (!hasDisjointValueRange(EnumDec, OtherEnumDec))
186  diag(DiffEnumOp->getOperatorLoc(), DifferentEnumErrorMessage);
187  return;
188  }
189 
190  // Case 2 and 3 only checked in strict mode. The checker tries to detect
191  // suspicious bitmasks which contains values initialized by non power-of-2
192  // literals.
193  if (!StrictMode)
194  return;
195  const auto *EnumDec = Result.Nodes.getNodeAs<EnumDecl>("enumDecl");
196  if (!isPossiblyBitMask(EnumDec))
197  return;
198 
199  // Case 2:
200  // a. Investigating the right hand side of `+=` or `|=` operator.
201  // b. When the operator is `|` or `+` but only one of them is an EnumExpr
202  if (const auto *EnumExpr = Result.Nodes.getNodeAs<Expr>("enumExpr")) {
203  checkSuspiciousBitmaskUsage(EnumExpr, EnumDec);
204  return;
205  }
206 
207  // Case 3:
208  // '|' or '+' operator where both argument comes from the same enum type
209  const auto *LhsExpr = Result.Nodes.getNodeAs<Expr>("lhsExpr");
210  checkSuspiciousBitmaskUsage(LhsExpr, EnumDec);
211 
212  const auto *RhsExpr = Result.Nodes.getNodeAs<Expr>("rhsExpr");
213  checkSuspiciousBitmaskUsage(RhsExpr, EnumDec);
214 }
215 
216 } // namespace bugprone
217 } // namespace tidy
218 } // namespace clang
static int enumLength(const EnumDecl *EnumDec)
Return the number of EnumConstantDecls in an EnumDecl.
static int countNonPowOfTwoLiteralNum(const EnumDecl *EnumDec)
static bool isPossiblyBitMask(const EnumDecl *EnumDec)
Check if there is one or two enumerators that are not a power of 2 and are initialized by a literal i...
Base class for all clang-tidy checks.
Stores a min and a max value which describe an interval.
static const char BitmaskErrorMessage[]
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.
static bool isMaxValAllBitSetLiteral(const EnumDecl *EnumDec)
static const char BitmaskVarErrorMessage[]
static constexpr llvm::StringLiteral Name
std::map< std::string, std::string > OptionMap
static const char BitmaskNoteMessage[]
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//
static bool isNonPowerOf2NorNullLiteral(const EnumConstantDecl *EnumConst)
Every ClangTidyCheck reports errors through a DiagnosticsEngine provided by this context.
llvm::Optional< llvm::Expected< tooling::AtomicChanges > > Result
Definition: Rename.cpp:36
void storeOptions(ClangTidyOptions::OptionMap &Opts) override
Should store all options supported by this check with their current values or default values for opti...
void registerMatchers(ast_matchers::MatchFinder *Finder) override
Override this to register AST matchers with Finder.
static const char DifferentEnumErrorMessage[]
void check(const ast_matchers::MatchFinder::MatchResult &Result) override
ClangTidyChecks that register ASTMatchers should do the actual work in here.
DiagnosticBuilder diag(SourceLocation Loc, StringRef Description, DiagnosticIDs::Level Level=DiagnosticIDs::Warning)
Add a diagnostic with the check&#39;s name.
static bool hasDisjointValueRange(const EnumDecl *Enum1, const EnumDecl *Enum2)