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   llvm::APSInt Index;
69   if (!IndexExpr->isIntegerConstantExpr(Index, *Result.Context, nullptr,
70                                         /*isEvaluated=*/true)) {
71     SourceRange BaseRange;
72     if (const auto *ArraySubscriptE = dyn_cast<ArraySubscriptExpr>(Matched))
73       BaseRange = ArraySubscriptE->getBase()->getSourceRange();
74     else
75       BaseRange =
76           dyn_cast<CXXOperatorCallExpr>(Matched)->getArg(0)->getSourceRange();
77     SourceRange IndexRange = IndexExpr->getSourceRange();
78 
79     auto Diag = diag(Matched->getExprLoc(),
80                      "do not use array subscript when the index is "
81                      "not an integer constant expression; use gsl::at() "
82                      "instead");
83     if (!GslHeader.empty()) {
84       Diag << FixItHint::CreateInsertion(BaseRange.getBegin(), "gsl::at(")
85            << FixItHint::CreateReplacement(
86                   SourceRange(BaseRange.getEnd().getLocWithOffset(1),
87                               IndexRange.getBegin().getLocWithOffset(-1)),
88                   ", ")
89            << FixItHint::CreateReplacement(Matched->getLocEnd(), ")");
90 
91       Optional<FixItHint> Insertion = Inserter->CreateIncludeInsertion(
92           Result.SourceManager->getMainFileID(), GslHeader,
93           /*IsAngled=*/false);
94       if (Insertion)
95         Diag << Insertion.getValue();
96     }
97     return;
98   }
99 
100   const auto *StdArrayDecl =
101       Result.Nodes.getNodeAs<ClassTemplateSpecializationDecl>("type");
102 
103   // For static arrays, this is handled in clang-diagnostic-array-bounds.
104   if (!StdArrayDecl)
105     return;
106 
107   if (Index.isSigned() && Index.isNegative()) {
108     diag(Matched->getExprLoc(),
109          "std::array<> index %0 is negative")
110         << Index.toString(10);
111     return;
112   }
113 
114   const TemplateArgumentList &TemplateArgs = StdArrayDecl->getTemplateArgs();
115   if (TemplateArgs.size() < 2)
116     return;
117   // First template arg of std::array is the type, second arg is the size.
118   const auto &SizeArg = TemplateArgs[1];
119   if (SizeArg.getKind() != TemplateArgument::Integral)
120     return;
121   llvm::APInt ArraySize = SizeArg.getAsIntegral();
122 
123   // Get uint64_t values, because different bitwidths would lead to an assertion
124   // in APInt::uge.
125   if (Index.getZExtValue() >= ArraySize.getZExtValue()) {
126     diag(Matched->getExprLoc(), "std::array<> index %0 is past the end of the array "
127                                 "(which contains %1 elements)")
128         << Index.toString(10) << ArraySize.toString(10, false);
129   }
130 }
131 
132 } // namespace cppcoreguidelines
133 } // namespace tidy
134 } // namespace clang
135