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 
15 using namespace clang::ast_matchers;
16 
17 namespace clang {
18 namespace tidy {
19 namespace cppcoreguidelines {
20 
21 ProBoundsConstantArrayIndexCheck::ProBoundsConstantArrayIndexCheck(
22     StringRef Name, ClangTidyContext *Context)
23     : ClangTidyCheck(Name, Context), GslHeader(Options.get("GslHeader", "")),
24       IncludeStyle(utils::IncludeSorter::parseIncludeStyle(
25           Options.getLocalOrGlobal("IncludeStyle", "llvm"))) {}
26 
27 void ProBoundsConstantArrayIndexCheck::storeOptions(
28     ClangTidyOptions::OptionMap &Opts) {
29   Options.store(Opts, "GslHeader", GslHeader);
30   Options.store(Opts, "IncludeStyle", IncludeStyle);
31 }
32 
33 void ProBoundsConstantArrayIndexCheck::registerPPCallbacks(
34     const SourceManager &SM, Preprocessor *PP, Preprocessor *ModuleExpanderPP) {
35   Inserter = std::make_unique<utils::IncludeInserter>(SM, getLangOpts(),
36                                                        IncludeStyle);
37   PP->addPPCallbacks(Inserter->CreatePPCallbacks());
38 }
39 
40 void ProBoundsConstantArrayIndexCheck::registerMatchers(MatchFinder *Finder) {
41   // Note: if a struct contains an array member, the compiler-generated
42   // constructor has an arraySubscriptExpr.
43   Finder->addMatcher(
44       arraySubscriptExpr(
45           hasBase(ignoringImpCasts(hasType(constantArrayType().bind("type")))),
46           hasIndex(expr().bind("index")), unless(hasAncestor(isImplicit())))
47           .bind("expr"),
48       this);
49 
50   Finder->addMatcher(
51       cxxOperatorCallExpr(
52           hasOverloadedOperatorName("[]"),
53           hasArgument(
54               0, hasType(cxxRecordDecl(hasName("::std::array")).bind("type"))),
55           hasArgument(1, expr().bind("index")))
56           .bind("expr"),
57       this);
58 }
59 
60 void ProBoundsConstantArrayIndexCheck::check(
61     const MatchFinder::MatchResult &Result) {
62   const auto *Matched = Result.Nodes.getNodeAs<Expr>("expr");
63   const auto *IndexExpr = Result.Nodes.getNodeAs<Expr>("index");
64 
65   if (IndexExpr->isValueDependent())
66     return; // We check in the specialization.
67 
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->getEndLoc(), ")");
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(), "std::array<> index %0 is negative")
109         << Index.toString(10);
110     return;
111   }
112 
113   const TemplateArgumentList &TemplateArgs = StdArrayDecl->getTemplateArgs();
114   if (TemplateArgs.size() < 2)
115     return;
116   // First template arg of std::array is the type, second arg is the size.
117   const auto &SizeArg = TemplateArgs[1];
118   if (SizeArg.getKind() != TemplateArgument::Integral)
119     return;
120   llvm::APInt ArraySize = SizeArg.getAsIntegral();
121 
122   // Get uint64_t values, because different bitwidths would lead to an assertion
123   // in APInt::uge.
124   if (Index.getZExtValue() >= ArraySize.getZExtValue()) {
125     diag(Matched->getExprLoc(),
126          "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