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