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

   1 //===--- ProBoundsArrayToPointerDecayCheck.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 "ProBoundsArrayToPointerDecayCheck.h"
  10 #include "clang/AST/ASTContext.h"
  11 #include "clang/AST/ParentMapContext.h"
  12 #include "clang/ASTMatchers/ASTMatchFinder.h"
  13
  14 using namespace clang::ast_matchers;
  15
  16 namespace clang::tidy::cppcoreguidelines {
  17
  18 namespace {
  19 AST_MATCHER_P(CXXForRangeStmt, hasRangeBeginEndStmt,
  20               ast_matchers::internal::Matcher<DeclStmt>, InnerMatcher) {
  21   for (const DeclStmt *Stmt : {Node.getBeginStmt(), Node.getEndStmt()})
  22     if (Stmt != nullptr && InnerMatcher.matches(*Stmt, Finder, Builder))
  23       return true;
  24   return false;
  25 }
  26
  27 AST_MATCHER(Stmt, isInsideOfRangeBeginEndStmt) {
  28   return stmt(hasAncestor(cxxForRangeStmt(
  29                   hasRangeBeginEndStmt(hasDescendant(equalsNode(&Node))))))
  30       .matches(Node, Finder, Builder);
  31 }
  32
  33 AST_MATCHER_P(Expr, hasParentIgnoringImpCasts,
  34               ast_matchers::internal::Matcher<Expr>, InnerMatcher) {
  35   const Expr *E = &Node;
  36   do {
  37     DynTypedNodeList Parents = Finder->getASTContext().getParents(*E);
  38     if (Parents.size() != 1)
  39       return false;
  40     E = Parents[0].get<Expr>();
  41     if (!E)
  42       return false;
  43   } while (isa<ImplicitCastExpr>(E));
  44
  45   return InnerMatcher.matches(*E, Finder, Builder);
  46 }
  47 } // namespace
  48
  49 void ProBoundsArrayToPointerDecayCheck::registerMatchers(MatchFinder *Finder) {
  50   // The only allowed array to pointer decay
  51   // 1) just before array subscription
  52   // 2) inside a range-for over an array
  53   // 3) if it converts a string literal to a pointer
  54   Finder->addMatcher(
  55       traverse(
  56           TK_AsIs,
  57           implicitCastExpr(
  58               unless(hasParent(arraySubscriptExpr())),
  59               unless(hasParentIgnoringImpCasts(explicitCastExpr())),
  60               unless(isInsideOfRangeBeginEndStmt()),
  61               unless(hasSourceExpression(ignoringParens(stringLiteral()))),
  62               unless(hasSourceExpression(ignoringParens(
  63                   conditionalOperator(hasTrueExpression(stringLiteral()),
  64                                       hasFalseExpression(stringLiteral()))))))
  65               .bind("cast")),
  66       this);
  67 }
  68
  69 void ProBoundsArrayToPointerDecayCheck::check(
  70     const MatchFinder::MatchResult &Result) {
  71   const auto *MatchedCast = Result.Nodes.getNodeAs<ImplicitCastExpr>("cast");
  72   if (MatchedCast->getCastKind() != CK_ArrayToPointerDecay)
  73     return;
  74
  75   diag(MatchedCast->getExprLoc(), "do not implicitly decay an array into a "
  76                                   "pointer; consider using gsl::array_view or "
  77                                   "an explicit cast instead");
  78 }
  79
  80 } // namespace clang::tidy::cppcoreguidelines