Commit bcd0798c authored by Gabor Horvath's avatar Gabor Horvath
Browse files

[LifetimeAnalysis] Fix PR44150 

References need somewhat special treatment. While copying a gsl::Pointer
will propagate the points-to set, creating an object from a reference
often behaves more like a dereference operation.

Differential Revision: https://reviews.llvm.org/D70755
parent 3d9b1128

clang/lib/Sema/SemaInit.cpp

+26 −7
Original line number Diff line number Diff line
@@ -6653,6 +6653,7 @@ struct IndirectLocalPathEntry { 
    VarInit,

    LValToRVal,

    LifetimeBoundCall,

    GslReferenceInit,

    GslPointerInit

  } Kind;

  Expr *E;
@@ -6783,12 +6784,24 @@ static bool shouldTrackFirstArgument(const FunctionDecl *FD) { 


static void handleGslAnnotatedTypes(IndirectLocalPath &Path, Expr *Call,

                                    LocalVisitor Visit) {

  auto VisitPointerArg = [&](const Decl *D, Expr *Arg) {

  auto VisitPointerArg = [&](const Decl *D, Expr *Arg, bool Value) {

    // We are not interested in the temporary base objects of gsl Pointers:

    //   Temp().ptr; // Here ptr might not dangle.

    if (isa<MemberExpr>(Arg->IgnoreImpCasts()))

      return;

    Path.push_back({IndirectLocalPathEntry::GslPointerInit, Arg, D});

    // Once we initialized a value with a reference, it can no longer dangle.

    if (!Value) {

      for (auto It = Path.rbegin(), End = Path.rend(); It != End; ++It) {

        if (It->Kind == IndirectLocalPathEntry::GslReferenceInit)

          continue;

        if (It->Kind == IndirectLocalPathEntry::GslPointerInit)

          return;

        break;

      }

    }

    Path.push_back({Value ? IndirectLocalPathEntry::GslPointerInit

                          : IndirectLocalPathEntry::GslReferenceInit,

                    Arg, D});

    if (Arg->isGLValue())

      visitLocalsRetainedByReferenceBinding(Path, Arg, RK_ReferenceBinding,

                                            Visit,
@@ -6802,18 +6815,21 @@ static void handleGslAnnotatedTypes(IndirectLocalPath &Path, Expr *Call, 
  if (auto *MCE = dyn_cast<CXXMemberCallExpr>(Call)) {

    const auto *MD = cast_or_null<CXXMethodDecl>(MCE->getDirectCallee());

    if (MD && shouldTrackImplicitObjectArg(MD))

      VisitPointerArg(MD, MCE->getImplicitObjectArgument());

      VisitPointerArg(MD, MCE->getImplicitObjectArgument(),

                      !MD->getReturnType()->isReferenceType());

    return;

  } else if (auto *OCE = dyn_cast<CXXOperatorCallExpr>(Call)) {

    FunctionDecl *Callee = OCE->getDirectCallee();

    if (Callee && Callee->isCXXInstanceMember() &&

        shouldTrackImplicitObjectArg(cast<CXXMethodDecl>(Callee)))

      VisitPointerArg(Callee, OCE->getArg(0));

      VisitPointerArg(Callee, OCE->getArg(0),

                      !Callee->getReturnType()->isReferenceType());

    return;

  } else if (auto *CE = dyn_cast<CallExpr>(Call)) {

    FunctionDecl *Callee = CE->getDirectCallee();

    if (Callee && shouldTrackFirstArgument(Callee))

      VisitPointerArg(Callee, CE->getArg(0));

      VisitPointerArg(Callee, CE->getArg(0),

                      !Callee->getReturnType()->isReferenceType());

    return;

  }
@@ -6821,7 +6837,7 @@ static void handleGslAnnotatedTypes(IndirectLocalPath &Path, Expr *Call, 
    const auto *Ctor = CCE->getConstructor();

    const CXXRecordDecl *RD = Ctor->getParent();

    if (CCE->getNumArgs() > 0 && RD->hasAttr<PointerAttr>())

      VisitPointerArg(Ctor->getParamDecl(0), CCE->getArgs()[0]);

      VisitPointerArg(Ctor->getParamDecl(0), CCE->getArgs()[0], true);

  }

}
@@ -7287,6 +7303,7 @@ static SourceRange nextPathEntryRange(const IndirectLocalPath &Path, unsigned I, 
    case IndirectLocalPathEntry::AddressOf:

    case IndirectLocalPathEntry::LValToRVal:

    case IndirectLocalPathEntry::LifetimeBoundCall:

    case IndirectLocalPathEntry::GslReferenceInit:

    case IndirectLocalPathEntry::GslPointerInit:

      // These exist primarily to mark the path as not permitting or

      // supporting lifetime extension.
@@ -7309,7 +7326,8 @@ static bool pathOnlyInitializesGslPointer(IndirectLocalPath &Path) { 
      continue;

    if (It->Kind == IndirectLocalPathEntry::AddressOf)

      continue;

    return It->Kind == IndirectLocalPathEntry::GslPointerInit;

    return It->Kind == IndirectLocalPathEntry::GslPointerInit ||

           It->Kind == IndirectLocalPathEntry::GslReferenceInit;

  }

  return false;

}
@@ -7532,6 +7550,7 @@ void Sema::checkInitializerLifetime(const InitializedEntity &Entity, 


      case IndirectLocalPathEntry::LifetimeBoundCall:

      case IndirectLocalPathEntry::GslPointerInit:

      case IndirectLocalPathEntry::GslReferenceInit:

        // FIXME: Consider adding a note for these.

        break;

clang/test/Sema/warn-lifetime-analysis-nocfg.cpp

+5 −0
Original line number Diff line number Diff line
@@ -450,3 +450,8 @@ MyIntPointer handleDerivedToBaseCast1(MySpecialIntPointer ptr) { 
MyIntPointer handleDerivedToBaseCast2(MyOwnerIntPointer ptr) {

  return ptr; // expected-warning {{address of stack memory associated with parameter 'ptr' returned}}

}



std::vector<int>::iterator noFalsePositiveWithVectorOfPointers() {

  std::vector<std::vector<int>::iterator> iters;

  return iters.at(0);

}