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   if (!getLangOpts().CPlusPlus)
36     return;
37 
38   Inserter = std::make_unique<utils::IncludeInserter>(SM, getLangOpts(),
39                                                        IncludeStyle);
40   PP->addPPCallbacks(Inserter->CreatePPCallbacks());
41 }
42 
43 void ProBoundsConstantArrayIndexCheck::registerMatchers(MatchFinder *Finder) {
44   if (!getLangOpts().CPlusPlus)
45     return;
46 
47   // Note: if a struct contains an array member, the compiler-generated
48   // constructor has an arraySubscriptExpr.
49   Finder->addMatcher(
50       arraySubscriptExpr(
51           hasBase(ignoringImpCasts(hasType(constantArrayType().bind("type")))),
52           hasIndex(expr().bind("index")), unless(hasAncestor(isImplicit())))
53           .bind("expr"),
54       this);
55 
56   Finder->addMatcher(
57       cxxOperatorCallExpr(
58           hasOverloadedOperatorName("[]"),
59           hasArgument(
60               0, hasType(cxxRecordDecl(hasName("::std::array")).bind("type"))),
61           hasArgument(1, expr().bind("index")))
62           .bind("expr"),
63       this);
64 }
65 
66 void ProBoundsConstantArrayIndexCheck::check(
67     const MatchFinder::MatchResult &Result) {
68   const auto *Matched = Result.Nodes.getNodeAs<Expr>("expr");
69   const auto *IndexExpr = Result.Nodes.getNodeAs<Expr>("index");
70 
71   if (IndexExpr->isValueDependent())
72     return; // We check in the specialization.
73 
74   llvm::APSInt Index;
75   if (!IndexExpr->isIntegerConstantExpr(Index, *Result.Context, nullptr,
76                                         /*isEvaluated=*/true)) {
77     SourceRange BaseRange;
78     if (const auto *ArraySubscriptE = dyn_cast<ArraySubscriptExpr>(Matched))
79       BaseRange = ArraySubscriptE->getBase()->getSourceRange();
80     else
81       BaseRange =
82           dyn_cast<CXXOperatorCallExpr>(Matched)->getArg(0)->getSourceRange();
83     SourceRange IndexRange = IndexExpr->getSourceRange();
84 
85     auto Diag = diag(Matched->getExprLoc(),
86                      "do not use array subscript when the index is "
87                      "not an integer constant expression; use gsl::at() "
88                      "instead");
89     if (!GslHeader.empty()) {
90       Diag << FixItHint::CreateInsertion(BaseRange.getBegin(), "gsl::at(")
91            << FixItHint::CreateReplacement(
92                   SourceRange(BaseRange.getEnd().getLocWithOffset(1),
93                               IndexRange.getBegin().getLocWithOffset(-1)),
94                   ", ")
95            << FixItHint::CreateReplacement(Matched->getEndLoc(), ")");
96 
97       Optional<FixItHint> Insertion = Inserter->CreateIncludeInsertion(
98           Result.SourceManager->getMainFileID(), GslHeader,
99           /*IsAngled=*/false);
100       if (Insertion)
101         Diag << Insertion.getValue();
102     }
103     return;
104   }
105 
106   const auto *StdArrayDecl =
107       Result.Nodes.getNodeAs<ClassTemplateSpecializationDecl>("type");
108 
109   // For static arrays, this is handled in clang-diagnostic-array-bounds.
110   if (!StdArrayDecl)
111     return;
112 
113   if (Index.isSigned() && Index.isNegative()) {
114     diag(Matched->getExprLoc(), "std::array<> index %0 is negative")
115         << Index.toString(10);
116     return;
117   }
118 
119   const TemplateArgumentList &TemplateArgs = StdArrayDecl->getTemplateArgs();
120   if (TemplateArgs.size() < 2)
121     return;
122   // First template arg of std::array is the type, second arg is the size.
123   const auto &SizeArg = TemplateArgs[1];
124   if (SizeArg.getKind() != TemplateArgument::Integral)
125     return;
126   llvm::APInt ArraySize = SizeArg.getAsIntegral();
127 
128   // Get uint64_t values, because different bitwidths would lead to an assertion
129   // in APInt::uge.
130   if (Index.getZExtValue() >= ArraySize.getZExtValue()) {
131     diag(Matched->getExprLoc(),
132          "std::array<> index %0 is past the end of the array "
133          "(which contains %1 elements)")
134         << Index.toString(10) << ArraySize.toString(10, false);
135   }
136 }
137 
138 } // namespace cppcoreguidelines
139 } // namespace tidy
140 } // namespace clang
141