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       Inserter(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", 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(
42       arraySubscriptExpr(
43           hasBase(ignoringImpCasts(hasType(constantArrayType().bind("type")))),
44           hasIndex(expr().bind("index")), unless(hasAncestor(isImplicit())))
45           .bind("expr"),
46       this);
47 
48   Finder->addMatcher(
49       cxxOperatorCallExpr(
50           hasOverloadedOperatorName("[]"),
51           hasArgument(
52               0, hasType(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   if (IndexExpr->isValueDependent())
64     return; // We check in the specialization.
65 
66   Optional<llvm::APSInt> Index =
67       IndexExpr->getIntegerConstantExpr(*Result.Context);
68   if (!Index) {
69     SourceRange BaseRange;
70     if (const auto *ArraySubscriptE = dyn_cast<ArraySubscriptExpr>(Matched))
71       BaseRange = ArraySubscriptE->getBase()->getSourceRange();
72     else
73       BaseRange =
74           dyn_cast<CXXOperatorCallExpr>(Matched)->getArg(0)->getSourceRange();
75     SourceRange IndexRange = IndexExpr->getSourceRange();
76 
77     auto Diag = diag(Matched->getExprLoc(),
78                      "do not use array subscript when the index is "
79                      "not an integer constant expression; use gsl::at() "
80                      "instead");
81     if (!GslHeader.empty()) {
82       Diag << FixItHint::CreateInsertion(BaseRange.getBegin(), "gsl::at(")
83            << FixItHint::CreateReplacement(
84                   SourceRange(BaseRange.getEnd().getLocWithOffset(1),
85                               IndexRange.getBegin().getLocWithOffset(-1)),
86                   ", ")
87            << FixItHint::CreateReplacement(Matched->getEndLoc(), ")")
88            << Inserter.createMainFileIncludeInsertion(GslHeader);
89     }
90     return;
91   }
92 
93   const auto *StdArrayDecl =
94       Result.Nodes.getNodeAs<ClassTemplateSpecializationDecl>("type");
95 
96   // For static arrays, this is handled in clang-diagnostic-array-bounds.
97   if (!StdArrayDecl)
98     return;
99 
100   if (Index->isSigned() && Index->isNegative()) {
101     diag(Matched->getExprLoc(), "std::array<> index %0 is negative")
102         << toString(*Index, 10);
103     return;
104   }
105 
106   const TemplateArgumentList &TemplateArgs = StdArrayDecl->getTemplateArgs();
107   if (TemplateArgs.size() < 2)
108     return;
109   // First template arg of std::array is the type, second arg is the size.
110   const auto &SizeArg = TemplateArgs[1];
111   if (SizeArg.getKind() != TemplateArgument::Integral)
112     return;
113   llvm::APInt ArraySize = SizeArg.getAsIntegral();
114 
115   // Get uint64_t values, because different bitwidths would lead to an assertion
116   // in APInt::uge.
117   if (Index->getZExtValue() >= ArraySize.getZExtValue()) {
118     diag(Matched->getExprLoc(),
119          "std::array<> index %0 is past the end of the array "
120          "(which contains %1 elements)")
121         << toString(*Index, 10) << toString(ArraySize, 10, false);
122   }
123 }
124 
125 } // namespace cppcoreguidelines
126 } // namespace tidy
127 } // namespace clang
128