1 //===--- RedundantPreprocessorCheck.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 #include "RedundantPreprocessorCheck.h"
10 #include "clang/Frontend/CompilerInstance.h"
11 #include "clang/Lex/Lexer.h"
12 #include "clang/Lex/PPCallbacks.h"
13 #include "clang/Lex/Preprocessor.h"
14 
15 namespace clang {
16 namespace tidy {
17 namespace readability {
18 
19 namespace {
20 /// Information about an opening preprocessor directive.
21 struct PreprocessorEntry {
22   SourceLocation Loc;
23   /// Condition used after the preprocessor directive.
24   std::string Condition;
25 };
26 
27 class RedundantPreprocessorCallbacks : public PPCallbacks {
28   enum DirectiveKind { DK_If = 0, DK_Ifdef = 1, DK_Ifndef = 2 };
29 
30 public:
31   explicit RedundantPreprocessorCallbacks(ClangTidyCheck &Check,
32                                           Preprocessor &PP)
33       : Check(Check), PP(PP),
34         WarningDescription("nested redundant %select{#if|#ifdef|#ifndef}0; "
35                            "consider removing it"),
36         NoteDescription("previous %select{#if|#ifdef|#ifndef}0 was here") {}
37 
38   void If(SourceLocation Loc, SourceRange ConditionRange,
39           ConditionValueKind ConditionValue) override {
40     StringRef Condition =
41         Lexer::getSourceText(CharSourceRange::getTokenRange(ConditionRange),
42                              PP.getSourceManager(), PP.getLangOpts());
43     checkMacroRedundancy(Loc, Condition, IfStack, DK_If, DK_If, true);
44   }
45 
46   void Ifdef(SourceLocation Loc, const Token &MacroNameTok,
47              const MacroDefinition &MacroDefinition) override {
48     std::string MacroName = PP.getSpelling(MacroNameTok);
49     checkMacroRedundancy(Loc, MacroName, IfdefStack, DK_Ifdef, DK_Ifdef, true);
50     checkMacroRedundancy(Loc, MacroName, IfndefStack, DK_Ifdef, DK_Ifndef,
51                          false);
52   }
53 
54   void Ifndef(SourceLocation Loc, const Token &MacroNameTok,
55               const MacroDefinition &MacroDefinition) override {
56     std::string MacroName = PP.getSpelling(MacroNameTok);
57     checkMacroRedundancy(Loc, MacroName, IfndefStack, DK_Ifndef, DK_Ifndef,
58                          true);
59     checkMacroRedundancy(Loc, MacroName, IfdefStack, DK_Ifndef, DK_Ifdef,
60                          false);
61   }
62 
63   void Endif(SourceLocation Loc, SourceLocation IfLoc) override {
64     if (!IfStack.empty() && IfLoc == IfStack.back().Loc)
65       IfStack.pop_back();
66     if (!IfdefStack.empty() && IfLoc == IfdefStack.back().Loc)
67       IfdefStack.pop_back();
68     if (!IfndefStack.empty() && IfLoc == IfndefStack.back().Loc)
69       IfndefStack.pop_back();
70   }
71 
72 private:
73   void checkMacroRedundancy(SourceLocation Loc, StringRef MacroName,
74                             SmallVector<PreprocessorEntry, 4> &Stack,
75                             DirectiveKind WarningKind, DirectiveKind NoteKind,
76                             bool Store) {
77     if (PP.getSourceManager().isInMainFile(Loc)) {
78       for (const auto &Entry : Stack) {
79         if (Entry.Condition == MacroName) {
80           Check.diag(Loc, WarningDescription) << WarningKind;
81           Check.diag(Entry.Loc, NoteDescription, DiagnosticIDs::Note)
82               << NoteKind;
83         }
84       }
85     }
86 
87     if (Store)
88       // This is an actual directive to be remembered.
89       Stack.push_back({Loc, std::string(MacroName)});
90   }
91 
92   ClangTidyCheck &Check;
93   Preprocessor &PP;
94   SmallVector<PreprocessorEntry, 4> IfStack;
95   SmallVector<PreprocessorEntry, 4> IfdefStack;
96   SmallVector<PreprocessorEntry, 4> IfndefStack;
97   const std::string WarningDescription;
98   const std::string NoteDescription;
99 };
100 } // namespace
101 
102 void RedundantPreprocessorCheck::registerPPCallbacks(
103     const SourceManager &SM, Preprocessor *PP, Preprocessor *ModuleExpanderPP) {
104   PP->addPPCallbacks(
105       ::std::make_unique<RedundantPreprocessorCallbacks>(*this, *PP));
106 }
107 
108 } // namespace readability
109 } // namespace tidy
110 } // namespace clang
111