clang-tools-extra/clang-tidy/cert/DefaultOperatorNewAlignmentCheck.cpp

   1 //===--- DefaultOperatorNewCheck.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 "DefaultOperatorNewAlignmentCheck.h"
  10 #include "clang/AST/ASTContext.h"
  11 #include "clang/ASTMatchers/ASTMatchFinder.h"
  12 #include "clang/Basic/TargetInfo.h"
  13
  14 using namespace clang::ast_matchers;
  15
  16 namespace clang::tidy::cert {
  17
  18 void DefaultOperatorNewAlignmentCheck::registerMatchers(MatchFinder *Finder) {
  19   Finder->addMatcher(
  20       cxxNewExpr(unless(hasAnyPlacementArg(anything()))).bind("new"), this);
  21 }
  22
  23 void DefaultOperatorNewAlignmentCheck::check(
  24     const MatchFinder::MatchResult &Result) {
  25   // Get the found 'new' expression.
  26   const auto *NewExpr = Result.Nodes.getNodeAs<CXXNewExpr>("new");
  27
  28   QualType T = NewExpr->getAllocatedType();
  29   // Dependent types do not have fixed alignment.
  30   if (T->isDependentType())
  31     return;
  32   const TagDecl *D = T->getAsTagDecl();
  33   // Alignment can not be obtained for undefined type.
  34   if (!D || !D->getDefinition() || !D->isCompleteDefinition())
  35     return;
  36
  37   ASTContext &Context = D->getASTContext();
  38
  39   // Check if no alignment was specified for the type.
  40   if (!Context.isAlignmentRequired(T))
  41     return;
  42
  43   // The user-specified alignment (in bits).
  44   unsigned SpecifiedAlignment = D->getMaxAlignment();
  45   // Double-check if no alignment was specified.
  46   if (!SpecifiedAlignment)
  47     return;
  48   // The alignment used by default 'operator new' (in bits).
  49   unsigned DefaultNewAlignment = Context.getTargetInfo().getNewAlign();
  50
  51   bool OverAligned = SpecifiedAlignment > DefaultNewAlignment;
  52   bool HasDefaultOperatorNew =
  53       !NewExpr->getOperatorNew() || NewExpr->getOperatorNew()->isImplicit();
  54
  55   unsigned CharWidth = Context.getTargetInfo().getCharWidth();
  56   if (HasDefaultOperatorNew && OverAligned)
  57     diag(NewExpr->getBeginLoc(),
  58          "allocation function returns a pointer with alignment %0 but the "
  59          "over-aligned type being allocated requires alignment %1")
  60         << (DefaultNewAlignment / CharWidth)
  61         << (SpecifiedAlignment / CharWidth);
  62 }
  63
  64 } // namespace clang::tidy::cert