LifetimeAnnotations.cpp

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//===- LifetimeAnnotations.cpp -  -*--------------- C++------------------*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "clang/Analysis/Analyses/LifetimeSafety/LifetimeAnnotations.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/Attr.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/Type.h"
#include "clang/AST/TypeLoc.h"
 
namespace clang::lifetimes {
 
const FunctionDecl *
getDeclWithMergedLifetimeBoundAttrs(const FunctionDecl *FD) {
  return FD != nullptr ? FD->getMostRecentDecl() : nullptr;
}
 
const CXXMethodDecl *
getDeclWithMergedLifetimeBoundAttrs(const CXXMethodDecl *CMD) {
  const FunctionDecl *FD = CMD;
  return cast_if_present<CXXMethodDecl>(
      getDeclWithMergedLifetimeBoundAttrs(FD));
}
 
bool isNormalAssignmentOperator(const FunctionDecl *FD) {
  OverloadedOperatorKind OO = FD->getDeclName().getCXXOverloadedOperator();
  bool IsAssignment = OO == OO_Equal || isCompoundAssignmentOperator(OO);
  if (!IsAssignment)
    return false;
  QualType RetT = FD->getReturnType();
  if (!RetT->isLValueReferenceType())
    return false;
  ASTContext &Ctx = FD->getASTContext();
  QualType LHST;
  auto *MD = dyn_cast<CXXMethodDecl>(FD);
  if (MD && MD->isCXXInstanceMember())
    LHST = Ctx.getLValueReferenceType(MD->getFunctionObjectParameterType());
  else
    LHST = FD->getParamDecl(0)->getType();
  return Ctx.hasSameType(RetT, LHST);
}
 
bool isAssignmentOperatorLifetimeBound(const CXXMethodDecl *CMD) {
  CMD = getDeclWithMergedLifetimeBoundAttrs(CMD);
  return CMD && isNormalAssignmentOperator(CMD) && CMD->param_size() == 1 &&
         CMD->getParamDecl(0)->hasAttr<clang::LifetimeBoundAttr>();
}
 
bool implicitObjectParamIsLifetimeBound(const FunctionDecl *FD) {
  FD = getDeclWithMergedLifetimeBoundAttrs(FD);
  const TypeSourceInfo *TSI = FD->getTypeSourceInfo();
  if (!TSI)
    return false;
  // Don't declare this variable in the second operand of the for-statement;
  // GCC miscompiles that by ending its lifetime before evaluating the
  // third operand. See gcc.gnu.org/PR86769.
  AttributedTypeLoc ATL;
  for (TypeLoc TL = TSI->getTypeLoc();
       (ATL = TL.getAsAdjusted<AttributedTypeLoc>());
       TL = ATL.getModifiedLoc()) {
    if (ATL.getAttrAs<clang::LifetimeBoundAttr>())
      return true;
  }
 
  return isNormalAssignmentOperator(FD);
}
 
template <typename T> static bool isRecordWithAttr(QualType Type) {
  auto *RD = Type->getAsCXXRecordDecl();
  if (!RD)
    return false;
  // Generally, if a primary template class declaration is annotated with an
  // attribute, all its specializations generated from template instantiations
  // should inherit the attribute.
  //
  // However, since lifetime analysis occurs during parsing, we may encounter
  // cases where a full definition of the specialization is not required. In
  // such cases, the specialization declaration remains incomplete and lacks the
  // attribute. Therefore, we fall back to checking the primary template class.
  //
  // Note: it is possible for a specialization declaration to have an attribute
  // even if the primary template does not.
  //
  // FIXME: What if the primary template and explicit specialization
  // declarations have conflicting attributes? We should consider diagnosing
  // this scenario.
  bool Result = RD->hasAttr<T>();
 
  if (auto *CTSD = dyn_cast<ClassTemplateSpecializationDecl>(RD))
    Result |= CTSD->getSpecializedTemplate()->getTemplatedDecl()->hasAttr<T>();
 
  return Result;
}
 
bool isGslPointerType(QualType QT) { return isRecordWithAttr<PointerAttr>(QT); }
bool isGslOwnerType(QualType QT) { return isRecordWithAttr<OwnerAttr>(QT); }
 
} // namespace clang::lifetimes