clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsConstantArrayIndexCheck.cpp

   1 //===--- ProBoundsConstantArrayIndexCheck.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 "ProBoundsConstantArrayIndexCheck.h"
  10 #include "clang/AST/ASTContext.h"
  11 #include "clang/ASTMatchers/ASTMatchFinder.h"
  12 #include "clang/Frontend/CompilerInstance.h"
  13 #include "clang/Lex/Preprocessor.h"
  14 #include <optional>
  15
  16 using namespace clang::ast_matchers;
  17
  18 namespace clang::tidy::cppcoreguidelines {
  19
  20 ProBoundsConstantArrayIndexCheck::ProBoundsConstantArrayIndexCheck(
  21     StringRef Name, ClangTidyContext *Context)
  22     : ClangTidyCheck(Name, Context), GslHeader(Options.get("GslHeader", "")),
  23       Inserter(Options.getLocalOrGlobal("IncludeStyle",
  24                                         utils::IncludeSorter::IS_LLVM),
  25                areDiagsSelfContained()) {}
  26
  27 void ProBoundsConstantArrayIndexCheck::storeOptions(
  28     ClangTidyOptions::OptionMap &Opts) {
  29   Options.store(Opts, "GslHeader", GslHeader);
  30   Options.store(Opts, "IncludeStyle", Inserter.getStyle());
  31 }
  32
  33 void ProBoundsConstantArrayIndexCheck::registerPPCallbacks(
  34     const SourceManager &SM, Preprocessor *PP, Preprocessor *ModuleExpanderPP) {
  35   Inserter.registerPreprocessor(PP);
  36 }
  37
  38 void ProBoundsConstantArrayIndexCheck::registerMatchers(MatchFinder *Finder) {
  39   // Note: if a struct contains an array member, the compiler-generated
  40   // constructor has an arraySubscriptExpr.
  41   Finder->addMatcher(arraySubscriptExpr(hasBase(ignoringImpCasts(hasType(
  42                                             constantArrayType().bind("type")))),
  43                                         hasIndex(expr().bind("index")),
  44                                         unless(hasAncestor(decl(isImplicit()))))
  45                          .bind("expr"),
  46                      this);
  47
  48   Finder->addMatcher(
  49       cxxOperatorCallExpr(
  50           hasOverloadedOperatorName("[]"),
  51           callee(cxxMethodDecl(
  52               ofClass(cxxRecordDecl(hasName("::std::array")).bind("type")))),
  53           hasArgument(1, expr().bind("index")))
  54           .bind("expr"),
  55       this);
  56 }
  57
  58 void ProBoundsConstantArrayIndexCheck::check(
  59     const MatchFinder::MatchResult &Result) {
  60   const auto *Matched = Result.Nodes.getNodeAs<Expr>("expr");
  61   const auto *IndexExpr = Result.Nodes.getNodeAs<Expr>("index");
  62
  63   // This expression can only appear inside ArrayInitLoopExpr, which
  64   // is always implicitly generated. ArrayInitIndexExpr is not a
  65   // constant, but we shouldn't report a warning for it.
  66   if (isa<ArrayInitIndexExpr>(IndexExpr))
  67     return;
  68
  69   if (IndexExpr->isValueDependent())
  70     return; // We check in the specialization.
  71
  72   std::optional<llvm::APSInt> Index =
  73       IndexExpr->getIntegerConstantExpr(*Result.Context);
  74   if (!Index) {
  75     SourceRange BaseRange;
  76     if (const auto *ArraySubscriptE = dyn_cast<ArraySubscriptExpr>(Matched))
  77       BaseRange = ArraySubscriptE->getBase()->getSourceRange();
  78     else
  79       BaseRange =
  80           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");
  86     if (!GslHeader.empty()) {
  87       Diag << FixItHint::CreateInsertion(BaseRange.getBegin(), "gsl::at(")
  88            << FixItHint::CreateReplacement(
  89                   SourceRange(BaseRange.getEnd().getLocWithOffset(1),
  90                               IndexRange.getBegin().getLocWithOffset(-1)),
  91                   ", ")
  92            << FixItHint::CreateReplacement(Matched->getEndLoc(), ")")
  93            << Inserter.createMainFileIncludeInsertion(GslHeader);
  94     }
  95     return;
  96   }
  97
  98   const auto *StdArrayDecl =
  99       Result.Nodes.getNodeAs<ClassTemplateSpecializationDecl>("type");
 100
 101   // For static arrays, this is handled in clang-diagnostic-array-bounds.
 102   if (!StdArrayDecl)
 103     return;
 104
 105   if (Index->isSigned() && Index->isNegative()) {
 106     diag(Matched->getExprLoc(), "std::array<> index %0 is negative")
 107         << toString(*Index, 10);
 108     return;
 109   }
 110
 111   const TemplateArgumentList &TemplateArgs = StdArrayDecl->getTemplateArgs();
 112   if (TemplateArgs.size() < 2)
 113     return;
 114   // First template arg of std::array is the type, second arg is the size.
 115   const auto &SizeArg = TemplateArgs[1];
 116   if (SizeArg.getKind() != TemplateArgument::Integral)
 117     return;
 118   llvm::APInt ArraySize = SizeArg.getAsIntegral();
 119
 120   // Get uint64_t values, because different bitwidths would lead to an assertion
 121   // in APInt::uge.
 122   if (Index->getZExtValue() >= ArraySize.getZExtValue()) {
 123     diag(Matched->getExprLoc(),
 124          "std::array<> index %0 is past the end of the array "
 125          "(which contains %1 elements)")
 126         << toString(*Index, 10) << toString(ArraySize, 10, false);
 127   }
 128 }
 129
 130 } // namespace clang::tidy::cppcoreguidelines