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1 //===--- MacroRepeatedSideEffectsCheck.cpp - clang-tidy--------------------===//
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2 //
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3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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4 // See https://llvm.org/LICENSE.txt for license information.
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5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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6 //
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7 //===----------------------------------------------------------------------===//
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8
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9 #include "MacroRepeatedSideEffectsCheck.h"
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10 #include "clang/Basic/Builtins.h"
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11 #include "clang/Frontend/CompilerInstance.h"
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12 #include "clang/Lex/MacroArgs.h"
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13 #include "clang/Lex/PPCallbacks.h"
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14 #include "clang/Lex/Preprocessor.h"
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15
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252
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16 namespace clang::tidy::bugprone {
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150
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17
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18 namespace {
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19 class MacroRepeatedPPCallbacks : public PPCallbacks {
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20 public:
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21 MacroRepeatedPPCallbacks(ClangTidyCheck &Check, Preprocessor &PP)
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22 : Check(Check), PP(PP) {}
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23
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24 void MacroExpands(const Token &MacroNameTok, const MacroDefinition &MD,
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25 SourceRange Range, const MacroArgs *Args) override;
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26
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27 private:
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28 ClangTidyCheck &Check;
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29 Preprocessor &PP;
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30
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31 unsigned countArgumentExpansions(const MacroInfo *MI,
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32 const IdentifierInfo *Arg) const;
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33
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34 bool hasSideEffects(const Token *ResultArgToks) const;
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35 };
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36 } // End of anonymous namespace.
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37
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38 void MacroRepeatedPPCallbacks::MacroExpands(const Token &MacroNameTok,
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39 const MacroDefinition &MD,
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40 SourceRange Range,
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41 const MacroArgs *Args) {
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42 // Ignore macro argument expansions.
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43 if (!Range.getBegin().isFileID())
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44 return;
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45
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46 const MacroInfo *MI = MD.getMacroInfo();
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47
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48 // Bail out if the contents of the macro are containing keywords that are
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49 // making the macro too complex.
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236
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50 if (llvm::any_of(MI->tokens(), [](const Token &T) {
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51 return T.isOneOf(tok::kw_if, tok::kw_else, tok::kw_switch, tok::kw_case,
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52 tok::kw_break, tok::kw_while, tok::kw_do, tok::kw_for,
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53 tok::kw_continue, tok::kw_goto, tok::kw_return);
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54 }))
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150
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55 return;
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56
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57 for (unsigned ArgNo = 0U; ArgNo < MI->getNumParams(); ++ArgNo) {
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58 const IdentifierInfo *Arg = *(MI->param_begin() + ArgNo);
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59 const Token *ResultArgToks = Args->getUnexpArgument(ArgNo);
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60
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61 if (hasSideEffects(ResultArgToks) &&
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62 countArgumentExpansions(MI, Arg) >= 2) {
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63 Check.diag(ResultArgToks->getLocation(),
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64 "side effects in the %ordinal0 macro argument %1 are "
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65 "repeated in macro expansion")
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66 << (ArgNo + 1) << Arg;
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67 Check.diag(MI->getDefinitionLoc(), "macro %0 defined here",
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68 DiagnosticIDs::Note)
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69 << MacroNameTok.getIdentifierInfo();
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70 }
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71 }
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72 }
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73
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74 unsigned MacroRepeatedPPCallbacks::countArgumentExpansions(
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75 const MacroInfo *MI, const IdentifierInfo *Arg) const {
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76 // Current argument count. When moving forward to a different control-flow
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77 // path this can decrease.
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78 unsigned Current = 0;
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79 // Max argument count.
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80 unsigned Max = 0;
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81 bool SkipParen = false;
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82 int SkipParenCount = 0;
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83 // Has a __builtin_constant_p been found?
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84 bool FoundBuiltin = false;
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85 bool PrevTokenIsHash = false;
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86 // Count when "?" is reached. The "Current" will get this value when the ":"
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87 // is reached.
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88 std::stack<unsigned, SmallVector<unsigned, 8>> CountAtQuestion;
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89 for (const auto &T : MI->tokens()) {
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90 // The result of __builtin_constant_p(x) is 0 if x is a macro argument
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91 // with side effects. If we see a __builtin_constant_p(x) followed by a
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92 // "?" "&&" or "||", then we need to reason about control flow to report
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93 // warnings correctly. Until such reasoning is added, bail out when this
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94 // happens.
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95 if (FoundBuiltin && T.isOneOf(tok::question, tok::ampamp, tok::pipepipe))
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96 return Max;
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97
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98 // Skip stringified tokens.
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99 if (T.is(tok::hash)) {
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100 PrevTokenIsHash = true;
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101 continue;
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102 }
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103 if (PrevTokenIsHash) {
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104 PrevTokenIsHash = false;
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105 continue;
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106 }
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107
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108 // Handling of ? and :.
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109 if (T.is(tok::question)) {
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110 CountAtQuestion.push(Current);
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111 } else if (T.is(tok::colon)) {
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112 if (CountAtQuestion.empty())
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113 return 0;
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114 Current = CountAtQuestion.top();
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115 CountAtQuestion.pop();
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116 }
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117
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118 // If current token is a parenthesis, skip it.
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119 if (SkipParen) {
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120 if (T.is(tok::l_paren))
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121 SkipParenCount++;
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122 else if (T.is(tok::r_paren))
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123 SkipParenCount--;
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124 SkipParen = (SkipParenCount != 0);
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125 if (SkipParen)
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126 continue;
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127 }
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128
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129 IdentifierInfo *TII = T.getIdentifierInfo();
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130 // If not existent, skip it.
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131 if (TII == nullptr)
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132 continue;
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133
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134 // If a __builtin_constant_p is found within the macro definition, don't
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135 // count arguments inside the parentheses and remember that it has been
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136 // seen in case there are "?", "&&" or "||" operators later.
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137 if (TII->getBuiltinID() == Builtin::BI__builtin_constant_p) {
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138 FoundBuiltin = true;
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139 SkipParen = true;
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140 continue;
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141 }
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142
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143 // If another macro is found within the macro definition, skip the macro
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144 // and the eventual arguments.
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145 if (TII->hasMacroDefinition()) {
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146 const MacroInfo *M = PP.getMacroDefinition(TII).getMacroInfo();
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147 if (M != nullptr && M->isFunctionLike())
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148 SkipParen = true;
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149 continue;
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150 }
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151
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152 // Count argument.
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153 if (TII == Arg) {
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154 Current++;
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155 if (Current > Max)
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156 Max = Current;
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157 }
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158 }
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159 return Max;
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160 }
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161
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162 bool MacroRepeatedPPCallbacks::hasSideEffects(
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163 const Token *ResultArgToks) const {
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164 for (; ResultArgToks->isNot(tok::eof); ++ResultArgToks) {
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165 if (ResultArgToks->isOneOf(tok::plusplus, tok::minusminus))
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166 return true;
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167 }
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168 return false;
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169 }
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170
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171 void MacroRepeatedSideEffectsCheck::registerPPCallbacks(
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172 const SourceManager &SM, Preprocessor *PP, Preprocessor *ModuleExpanderPP) {
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173 PP->addPPCallbacks(::std::make_unique<MacroRepeatedPPCallbacks>(*this, *PP));
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174 }
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175
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252
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176 } // namespace clang::tidy::bugprone
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