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 #include "clang/ASTMatchers/ASTMatchers.h"
  14
  15 using namespace clang::ast_matchers;
  16
  17 namespace clang::tidy::cppcoreguidelines {
  18
  19 namespace {
  20 AST_MATCHER_P(CXXForRangeStmt, hasRangeBeginEndStmt,
  21               ast_matchers::internal::Matcher<DeclStmt>, InnerMatcher) {
  22   for (const DeclStmt *Stmt : {Node.getBeginStmt(), Node.getEndStmt()})
  23     if (Stmt != nullptr && InnerMatcher.matches(*Stmt, Finder, Builder))
  24       return true;
  25   return false;
  26 }
  27
  28 AST_MATCHER(Stmt, isInsideOfRangeBeginEndStmt) {
  29   return stmt(hasAncestor(cxxForRangeStmt(
  30                   hasRangeBeginEndStmt(hasDescendant(equalsNode(&Node))))))
  31       .matches(Node, Finder, Builder);
  32 }
  33
  34 AST_MATCHER_P(Expr, hasParentIgnoringImpCasts,
  35               ast_matchers::internal::Matcher<Expr>, InnerMatcher) {
  36   const Expr *E = &Node;
  37   do {
  38     DynTypedNodeList Parents = Finder->getASTContext().getParents(*E);
  39     if (Parents.size() != 1)
  40       return false;
  41     E = Parents[0].get<Expr>();
  42     if (!E)
  43       return false;
  44   } while (isa<ImplicitCastExpr>(E));
  45
  46   return InnerMatcher.matches(*E, Finder, Builder);
  47 }
  48 } // namespace
  49
  50 void ProBoundsArrayToPointerDecayCheck::registerMatchers(MatchFinder *Finder) {
  51   // The only allowed array to pointer decay
  52   // 1) just before array subscription
  53   // 2) inside a range-for over an array
  54   // 3) if it converts a string literal to a pointer
  55   Finder->addMatcher(
  56       traverse(
  57           TK_AsIs,
  58           implicitCastExpr(
  59               unless(hasParent(arraySubscriptExpr())),
  60               unless(hasSourceExpression(predefinedExpr())),
  61               unless(hasParentIgnoringImpCasts(explicitCastExpr())),
  62               unless(isInsideOfRangeBeginEndStmt()),
  63               unless(hasSourceExpression(ignoringParens(stringLiteral()))),
  64               unless(hasSourceExpression(ignoringParens(
  65                   conditionalOperator(hasTrueExpression(stringLiteral()),
  66                                       hasFalseExpression(stringLiteral()))))))
  67               .bind("cast")),
  68       this);
  69 }
  70
  71 void ProBoundsArrayToPointerDecayCheck::check(
  72     const MatchFinder::MatchResult &Result) {
  73   const auto *MatchedCast = Result.Nodes.getNodeAs<ImplicitCastExpr>("cast");
  74   if (MatchedCast->getCastKind() != CK_ArrayToPointerDecay)
  75     return;
  76
  77   diag(MatchedCast->getExprLoc(), "do not implicitly decay an array into a "
  78                                   "pointer; consider using gsl::array_view or "
  79                                   "an explicit cast instead");
  80 }
  81
  82 } // namespace clang::tidy::cppcoreguidelines