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(Options.getLocalOrGlobal("IncludeStyle",
25                                             utils::IncludeSorter::IS_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   Optional<llvm::APSInt> Index =
69       IndexExpr->getIntegerConstantExpr(*Result.Context);
70   if (!Index) {
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            << Inserter->CreateIncludeInsertion(
91                   Result.SourceManager->getMainFileID(), GslHeader,
92                   /*IsAngled=*/false);
93     }
94     return;
95   }
96 
97   const auto *StdArrayDecl =
98       Result.Nodes.getNodeAs<ClassTemplateSpecializationDecl>("type");
99 
100   // For static arrays, this is handled in clang-diagnostic-array-bounds.
101   if (!StdArrayDecl)
102     return;
103 
104   if (Index->isSigned() && Index->isNegative()) {
105     diag(Matched->getExprLoc(), "std::array<> index %0 is negative")
106         << Index->toString(10);
107     return;
108   }
109 
110   const TemplateArgumentList &TemplateArgs = StdArrayDecl->getTemplateArgs();
111   if (TemplateArgs.size() < 2)
112     return;
113   // First template arg of std::array is the type, second arg is the size.
114   const auto &SizeArg = TemplateArgs[1];
115   if (SizeArg.getKind() != TemplateArgument::Integral)
116     return;
117   llvm::APInt ArraySize = SizeArg.getAsIntegral();
118 
119   // Get uint64_t values, because different bitwidths would lead to an assertion
120   // in APInt::uge.
121   if (Index->getZExtValue() >= ArraySize.getZExtValue()) {
122     diag(Matched->getExprLoc(),
123          "std::array<> index %0 is past the end of the array "
124          "(which contains %1 elements)")
125         << Index->toString(10) << ArraySize.toString(10, false);
126   }
127 }
128 
129 } // namespace cppcoreguidelines
130 } // namespace tidy
131 } // namespace clang
132