1 //===--- ProBoundsConstantArrayIndexCheck.cpp - clang-tidy-----------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #include "ProBoundsConstantArrayIndexCheck.h"
11 #include "clang/AST/ASTContext.h"
12 #include "clang/ASTMatchers/ASTMatchFinder.h"
13 #include "clang/Frontend/CompilerInstance.h"
14 #include "clang/Lex/Preprocessor.h"
15 
16 using namespace clang::ast_matchers;
17 
18 namespace clang {
19 namespace tidy {
20 namespace cppcoreguidelines {
21 
22 ProBoundsConstantArrayIndexCheck::ProBoundsConstantArrayIndexCheck(
23     StringRef Name, ClangTidyContext *Context)
24     : ClangTidyCheck(Name, Context), GslHeader(Options.get("GslHeader", "")),
25       IncludeStyle(utils::IncludeSorter::parseIncludeStyle(
26           Options.get("IncludeStyle", "llvm"))) {}
27 
28 void ProBoundsConstantArrayIndexCheck::storeOptions(
29     ClangTidyOptions::OptionMap &Opts) {
30   Options.store(Opts, "GslHeader", GslHeader);
31   Options.store(Opts, "IncludeStyle", IncludeStyle);
32 }
33 
34 void ProBoundsConstantArrayIndexCheck::registerPPCallbacks(
35     CompilerInstance &Compiler) {
36   if (!getLangOpts().CPlusPlus)
37     return;
38 
39   Inserter.reset(new utils::IncludeInserter(
40       Compiler.getSourceManager(), Compiler.getLangOpts(), IncludeStyle));
41   Compiler.getPreprocessor().addPPCallbacks(Inserter->CreatePPCallbacks());
42 }
43 
44 void ProBoundsConstantArrayIndexCheck::registerMatchers(MatchFinder *Finder) {
45   if (!getLangOpts().CPlusPlus)
46     return;
47 
48   Finder->addMatcher(arraySubscriptExpr(hasBase(ignoringImpCasts(hasType(
49                                             constantArrayType().bind("type")))),
50                                         hasIndex(expr().bind("index")))
51                          .bind("expr"),
52                      this);
53 
54   Finder->addMatcher(
55       cxxOperatorCallExpr(
56           hasOverloadedOperatorName("[]"),
57           hasArgument(
58               0, hasType(cxxRecordDecl(hasName("::std::array")).bind("type"))),
59           hasArgument(1, expr().bind("index")))
60           .bind("expr"),
61       this);
62 }
63 
64 void ProBoundsConstantArrayIndexCheck::check(
65     const MatchFinder::MatchResult &Result) {
66   const auto *Matched = Result.Nodes.getNodeAs<Expr>("expr");
67   const auto *IndexExpr = Result.Nodes.getNodeAs<Expr>("index");
68 
69   if (IndexExpr->isValueDependent())
70     return; // We check in the specialization.
71 
72   llvm::APSInt Index;
73   if (!IndexExpr->isIntegerConstantExpr(Index, *Result.Context, nullptr,
74                                         /*isEvaluated=*/true)) {
75     SourceRange BaseRange;
76     if (const auto *ArraySubscriptE = dyn_cast<ArraySubscriptExpr>(Matched))
77       BaseRange = ArraySubscriptE->getBase()->getSourceRange();
78     else
79       BaseRange =
80           dyn_cast<CXXOperatorCallExpr>(Matched)->getArg(0)->getSourceRange();
81     SourceRange IndexRange = IndexExpr->getSourceRange();
82 
83     auto Diag = diag(Matched->getExprLoc(),
84                      "do not use array subscript when the index is "
85                      "not an integer constant expression; use gsl::at() "
86                      "instead");
87     if (!GslHeader.empty()) {
88       Diag << FixItHint::CreateInsertion(BaseRange.getBegin(), "gsl::at(")
89            << FixItHint::CreateReplacement(
90                   SourceRange(BaseRange.getEnd().getLocWithOffset(1),
91                               IndexRange.getBegin().getLocWithOffset(-1)),
92                   ", ")
93            << FixItHint::CreateReplacement(Matched->getLocEnd(), ")");
94 
95       Optional<FixItHint> Insertion = Inserter->CreateIncludeInsertion(
96           Result.SourceManager->getMainFileID(), GslHeader,
97           /*IsAngled=*/false);
98       if (Insertion)
99         Diag << Insertion.getValue();
100     }
101     return;
102   }
103 
104   const auto *StdArrayDecl =
105       Result.Nodes.getNodeAs<ClassTemplateSpecializationDecl>("type");
106 
107   // For static arrays, this is handled in clang-diagnostic-array-bounds.
108   if (!StdArrayDecl)
109     return;
110 
111   if (Index.isSigned() && Index.isNegative()) {
112     diag(Matched->getExprLoc(),
113          "std::array<> index %0 is negative")
114         << Index.toString(10);
115     return;
116   }
117 
118   const TemplateArgumentList &TemplateArgs = StdArrayDecl->getTemplateArgs();
119   if (TemplateArgs.size() < 2)
120     return;
121   // First template arg of std::array is the type, second arg is the size.
122   const auto &SizeArg = TemplateArgs[1];
123   if (SizeArg.getKind() != TemplateArgument::Integral)
124     return;
125   llvm::APInt ArraySize = SizeArg.getAsIntegral();
126 
127   // Get uint64_t values, because different bitwidths would lead to an assertion
128   // in APInt::uge.
129   if (Index.getZExtValue() >= ArraySize.getZExtValue()) {
130     diag(Matched->getExprLoc(), "std::array<> index %0 is past the end of the array "
131                                 "(which contains %1 elements)")
132         << Index.toString(10) << ArraySize.toString(10, false);
133   }
134 }
135 
136 } // namespace cppcoreguidelines
137 } // namespace tidy
138 } // namespace clang
139