diff --git a/bindings/jupyroot/python/JupyROOT/helpers/cppcompleter.py b/bindings/jupyroot/python/JupyROOT/helpers/cppcompleter.py
index b9f622c3292f5..f8ec85031148b 100644
--- a/bindings/jupyroot/python/JupyROOT/helpers/cppcompleter.py
+++ b/bindings/jupyroot/python/JupyROOT/helpers/cppcompleter.py
@@ -75,6 +75,7 @@ class CppCompleter(object):
     ...     print(suggestion)
     TROOT::IsA
     TROOT::IsBatch
+    TROOT::IsDestructed
     TROOT::IsEqual
     TROOT::IsEscaped
     TROOT::IsExecutingMacro
diff --git a/bindings/pyroot_legacy/JupyROOT/helpers/cppcompleter.py b/bindings/pyroot_legacy/JupyROOT/helpers/cppcompleter.py
index 5ab9d96f2df41..aa966442387f2 100644
--- a/bindings/pyroot_legacy/JupyROOT/helpers/cppcompleter.py
+++ b/bindings/pyroot_legacy/JupyROOT/helpers/cppcompleter.py
@@ -87,6 +87,7 @@ class CppCompleter(object):
     ...     print(suggestion)
     TROOT::IsA
     TROOT::IsBatch
+    TROOT::IsDestructed
     TROOT::IsEqual
     TROOT::IsEscaped
     TROOT::IsExecutingMacro
diff --git a/core/base/inc/TObject.h b/core/base/inc/TObject.h
index 08d2f865b58c8..3942f0f5e7ddc 100644
--- a/core/base/inc/TObject.h
+++ b/core/base/inc/TObject.h
@@ -33,6 +33,10 @@ class TObjArray;
 class TMethod;
 class TTimer;
 
+namespace ROOT {
+namespace Internal {
+   bool DeleteChangesMemoryImpl();
+}}
 
 class TObject {
 
@@ -163,6 +167,16 @@ class TObject {
    virtual Int_t       Write(const char *name = nullptr, Int_t option = 0, Int_t bufsize = 0);
    virtual Int_t       Write(const char *name = nullptr, Int_t option = 0, Int_t bufsize = 0) const;
 
+   /// IsDestructed
+   ///
+   /// \note This function must be non-virtual as it can be used on destructed (but
+   /// not yet modified) memory.  This is used for example in TClonesArray to record
+   /// the element that have been destructed but not deleted and thus are ready for
+   /// re-use (by operator new with placement).
+   ///
+   /// \return true if this object's destructor has been run.
+   Bool_t IsDestructed() const { return !TestBit(kNotDeleted); }
+
    //----- operators
    void    *operator new(size_t sz) { return TStorage::ObjectAlloc(sz); }
    void    *operator new[](size_t sz) { return TStorage::ObjectAllocArray(sz); }
@@ -226,6 +240,7 @@ class TObject {
    static void      SetObjectStat(Bool_t stat);
 
    friend class TClonesArray; // needs to reset kNotDeleted in fBits
+   friend bool ROOT::Internal::DeleteChangesMemoryImpl();
 
    ClassDef(TObject,1)  //Basic ROOT object
 };
@@ -365,4 +380,31 @@ namespace cling {
    std::string printValue(TObject *val);
 }
 
+namespace ROOT {
+
+namespace Internal {
+   bool DeleteChangesMemory();
+} // Internal
+
+namespace Detail {
+
+
+/// @brief Check if the TObject's memory has been deleted.
+/// @warning This should be only used for error mitigation as the answer is only
+///    sometimes correct.  It actually just checks whether the object has been
+///    deleted, so this will falsely return true for an object that has
+///    been destructed but its memory has not been deleted.  This will return an
+///    undefined value if the memory is re-used between the deletion and the check.
+///    i.e.  This is useful to prevent a segmentation fault in case where the problem
+///    can be detected when the deletion and the usage are 'close-by'
+/// @warning In enviroment where delete taints (changes) the memory, this function
+///    always returns false as the marker left by ~TObject will be overwritten.
+/// @param obj The memory to check
+/// @return true if the object has been destructed and it can be inferred that it has been deleted
+R__ALWAYS_INLINE bool HasBeenDeleted(const TObject *obj) {
+   return !ROOT::Internal::DeleteChangesMemory() && obj->IsDestructed();
+}
+
+}} // ROOT::Details
+
 #endif
diff --git a/core/base/src/TObject.cxx b/core/base/src/TObject.cxx
index 4496d881ca78d..523690b925cf4 100644
--- a/core/base/src/TObject.cxx
+++ b/core/base/src/TObject.cxx
@@ -56,6 +56,76 @@ Bool_t TObject::fgObjectStat = kTRUE;
 
 ClassImp(TObject);
 
+namespace ROOT {
+namespace Internal {
+
+// Return true if delete changes/poisons/taints the memory.
+//
+// Detect whether operator delete taints the memory. If it does, we can not rely
+// on TestBit(kNotDeleted) to check if the memory has been deleted (but in case,
+// like TClonesArray, where we know the destructor will be called but not operator
+// delete, we can still use it to detect the cases where the destructor was called.
+
+bool DeleteChangesMemoryImpl()
+{
+   static constexpr UInt_t kGoldenUUID = 0x00000021;
+   static constexpr UInt_t kGoldenbits = 0x03000000;
+ 
+   TObject *o = new TObject;
+   o->SetUniqueID(kGoldenUUID);
+   UInt_t *o_fuid = &(o->fUniqueID);
+   UInt_t *o_fbits = &(o->fBits);
+
+   if (*o_fuid != kGoldenUUID) {
+      Error("CheckingDeleteSideEffects",
+            "fUniqueID is not as expected, we got 0x%.8x instead of 0x%.8x",
+            *o_fuid, kGoldenUUID);
+   }
+   if (*o_fbits != kGoldenbits) {
+      Error("CheckingDeleteSideEffects",
+            "fBits is not as expected, we got 0x%.8x instead of 0x%.8x",
+            *o_fbits, kGoldenbits);
+   }
+   if (gDebug >= 9) {
+      unsigned char *oc = reinterpret_cast<unsigned char *>(o); // for address calculations
+      unsigned char references[sizeof(TObject)];
+      memcpy(references, oc, sizeof(TObject));
+
+      // The effective part of this code (the else statement is just that without
+      // any of the debug statement)
+      delete o;
+
+      // Not using the error logger, as there routine is meant to be called
+      // during library initialization/loading.
+      fprintf(stderr,
+              "DEBUG: Checking before and after delete the content of a TObject with uniqueID 0x21\n");
+      for(size_t i = 0; i < sizeof(TObject); i += 4) {
+        fprintf(stderr, "DEBUG: 0x%.8x vs 0x%.8x\n", *(int*)(references +i), *(int*)(oc + i));
+      }
+   } else
+      delete o;  // the 'if' part is that surrounded by the debug code.
+
+   // Intentionally accessing the deleted memory to check whether it has been changed as
+   // a consequence (side effect) of executing operator delete.  If there no change, we
+   // can guess this is always the case and we can rely on the changes to fBits made
+   // by ~TObject to detect use-after-delete error (and print a message rather than
+   // stop the program with a segmentation fault)
+   if ( *o_fbits != 0x01000000 ) {
+      // operator delete tainted the memory, we can not rely on TestBit(kNotDeleted)
+      return true;
+   }
+   return false;
+}
+
+bool DeleteChangesMemory()
+{
+   static const bool value = DeleteChangesMemoryImpl();
+   if (gDebug >= 9)
+      DeleteChangesMemoryImpl(); // To allow for printing the debug info
+   return value;
+}
+
+}} // ROOT::Detail
 
 ////////////////////////////////////////////////////////////////////////////////
 /// Copy this to obj.
diff --git a/core/base/src/TQConnection.cxx b/core/base/src/TQConnection.cxx
index 448dbb922cbf9..16cd3c5653e39 100644
--- a/core/base/src/TQConnection.cxx
+++ b/core/base/src/TQConnection.cxx
@@ -284,7 +284,7 @@ CallFunc_t *TQSlot::StartExecuting() {
 
 void TQSlot::EndExecuting() {
    fExecuting--;
-   if (!TestBit(kNotDeleted) && !fExecuting)
+   if (ROOT::Detail::HasBeenDeleted(this) && !fExecuting)
       gCling->CallFunc_Delete(fFunc);
 }
 
@@ -344,7 +344,7 @@ inline void TQSlot::ExecuteMethod(void *object, Longptr_t *paramArr, Int_t npara
    fExecuting++;
    gCling->CallFunc_Exec(fFunc, address);
    fExecuting--;
-   if (!TestBit(kNotDeleted) && !fExecuting)
+   if (ROOT::Detail::HasBeenDeleted(this) && !fExecuting)
       gCling->CallFunc_Delete(fFunc);
 }
 
diff --git a/core/base/src/TROOT.cxx b/core/base/src/TROOT.cxx
index a09aa34f251a9..d7e218bbd3038 100644
--- a/core/base/src/TROOT.cxx
+++ b/core/base/src/TROOT.cxx
@@ -1371,7 +1371,7 @@ TObject *TROOT::FindSpecialObject(const char *name, void *&where)
       }
    }
    if (!temp) return nullptr;
-   if (temp->TestBit(kNotDeleted)) return temp;
+   if (!ROOT::Detail::HasBeenDeleted(temp)) return temp;
    return nullptr;
 }
 
diff --git a/core/cont/src/TClonesArray.cxx b/core/cont/src/TClonesArray.cxx
index 5f0620880c2c6..623570b02e353 100644
--- a/core/cont/src/TClonesArray.cxx
+++ b/core/cont/src/TClonesArray.cxx
@@ -156,7 +156,7 @@ bool R__SetClonesArrayTFormulaUpdater(Updater_t func) {
 /// Internal Utility routine to correctly release the memory for an object
 static inline void R__ReleaseMemory(TClass *cl, TObject *obj)
 {
-   if (obj && obj->TestBit(TObject::kNotDeleted)) {
+   if (obj && ! obj->IsDestructed()) {
       // -- The TObject destructor has not been called.
       cl->Destructor(obj);
    } else {
@@ -366,7 +366,7 @@ void TClonesArray::Compress()
 TObject *TClonesArray::ConstructedAt(Int_t idx)
 {
    TObject *obj = (*this)[idx];
-   if ( obj && obj->TestBit(TObject::kNotDeleted) ) {
+   if ( obj && ! obj->IsDestructed() ) {
       return obj;
    }
    return (fClass) ? static_cast<TObject*>(fClass->New(obj)) : nullptr;
@@ -388,7 +388,7 @@ TObject *TClonesArray::ConstructedAt(Int_t idx)
 TObject *TClonesArray::ConstructedAt(Int_t idx, Option_t *clear_options)
 {
    TObject *obj = (*this)[idx];
-   if ( obj && obj->TestBit(TObject::kNotDeleted) ) {
+   if ( obj && !obj->IsDestructed() ) {
       obj->Clear(clear_options);
       return obj;
    }
@@ -444,13 +444,13 @@ void TClonesArray::Delete(Option_t *)
       // In case of emulated class, we can not use the delete operator
       // directly, it would use the wrong destructor.
       for (Int_t i = 0; i < fSize; i++) {
-         if (fCont[i] && fCont[i]->TestBit(kNotDeleted)) {
+         if (fCont[i] && ! fCont[i]->IsDestructed()) {
             fClass->Destructor(fCont[i],kTRUE);
          }
       }
    } else {
       for (Int_t i = 0; i < fSize; i++) {
-         if (fCont[i] && fCont[i]->TestBit(kNotDeleted)) {
+         if (fCont[i] && ! fCont[i]->IsDestructed()) {
             fCont[i]->~TObject();
          }
       }
@@ -516,7 +516,7 @@ void TClonesArray::ExpandCreate(Int_t n)
    for (i = 0; i < n; i++) {
       if (!fKeep->fCont[i]) {
          fKeep->fCont[i] = (TObject*)fClass->New();
-      } else if (!fKeep->fCont[i]->TestBit(kNotDeleted)) {
+      } else if (fKeep->fCont[i]->IsDestructed()) {
          // The object has been deleted (or never initialized)
          fClass->New(fKeep->fCont[i]);
       }
@@ -553,7 +553,7 @@ void TClonesArray::ExpandCreateFast(Int_t n)
    for (i = 0; i < n; i++) {
       if (i >= oldSize || !fKeep->fCont[i]) {
          fKeep->fCont[i] = (TObject*)fClass->New();
-      } else if (!fKeep->fCont[i]->TestBit(kNotDeleted)) {
+      } else if (fKeep->fCont[i]->IsDestructed()) {
          // The object has been deleted (or never initialized)
          fClass->New(fKeep->fCont[i]);
       }
@@ -575,7 +575,7 @@ TObject *TClonesArray::RemoveAt(Int_t idx)
 
    int i = idx-fLowerBound;
 
-   if (fCont[i] && fCont[i]->TestBit(kNotDeleted)) {
+   if (fCont[i] && ! fCont[i]->IsDestructed()) {
       fCont[i]->~TObject();
    }
 
@@ -601,7 +601,7 @@ TObject *TClonesArray::Remove(TObject *obj)
 
    if (i == -1) return nullptr;
 
-   if (fCont[i] && fCont[i]->TestBit(kNotDeleted)) {
+   if (fCont[i] && ! fCont[i]->IsDestructed()) {
       fCont[i]->~TObject();
    }
 
@@ -627,7 +627,7 @@ void TClonesArray::RemoveRange(Int_t idx1, Int_t idx2)
    Bool_t change = kFALSE;
    for (TObject **obj = fCont+idx1; obj <= fCont+idx2; obj++) {
       if (!*obj) continue;
-      if ((*obj)->TestBit(kNotDeleted)) {
+      if (!(*obj)->IsDestructed()) {
          (*obj)->~TObject();
       }
       *obj = nullptr;
@@ -801,7 +801,7 @@ void TClonesArray::Streamer(TBuffer &b)
          for (Int_t i = 0; i < nobjects; i++) {
             if (!fKeep->fCont[i]) {
                fKeep->fCont[i] = (TObject*)fClass->New();
-            } else if (!fKeep->fCont[i]->TestBit(kNotDeleted)) {
+            } else if (fKeep->fCont[i]->IsDestructed()) {
                // The object has been deleted (or never initialized)
                fClass->New(fKeep->fCont[i]);
             }
@@ -836,7 +836,7 @@ void TClonesArray::Streamer(TBuffer &b)
             if (nch) {
                if (!fKeep->fCont[i])
                   fKeep->fCont[i] = (TObject*)fClass->New();
-               else if (!fKeep->fCont[i]->TestBit(kNotDeleted)) {
+               else if (fKeep->fCont[i]->IsDestructed()) {
                   // The object has been deleted (or never initialized)
                   fClass->New(fKeep->fCont[i]);
                }
@@ -922,7 +922,7 @@ TObject *&TClonesArray::operator[](Int_t idx)
       fKeep->fCont[idx] = (TObject*) TStorage::ObjectAlloc(fClass->Size());
       // Reset the bit so that:
       //    obj = myClonesArray[i];
-      //    obj->TestBit(TObject::kNotDeleted)
+      //    ! obj->IsDestructed()
       // will behave correctly.
       // TObject::kNotDeleted is one of the higher bit that is not settable via the public
       // interface. But luckily we are its friend.
diff --git a/core/cont/src/TCollection.cxx b/core/cont/src/TCollection.cxx
index 5c5190ef148b6..ea8da3b25ed79 100644
--- a/core/cont/src/TCollection.cxx
+++ b/core/cont/src/TCollection.cxx
@@ -584,7 +584,7 @@ void TCollection::RecursiveRemove(TObject *obj)
    TObject *object;
 
    while ((object = next())) {
-      if (object->TestBit(kNotDeleted)) object->RecursiveRemove(obj);
+      if (!ROOT::Detail::HasBeenDeleted(object)) object->RecursiveRemove(obj);
    }
 }
 
diff --git a/core/cont/src/THashList.cxx b/core/cont/src/THashList.cxx
index aa2e8688a9b4e..83d139b832ed0 100644
--- a/core/cont/src/THashList.cxx
+++ b/core/cont/src/THashList.cxx
@@ -227,7 +227,7 @@ void THashList::Delete(Option_t *option)
          auto obj = tlk->GetObject();
          // In case somebody else access it.
          tlk->SetObject(nullptr);
-         if (obj && !obj->TestBit(kNotDeleted))
+         if (obj && ROOT::Detail::HasBeenDeleted(obj))
             Error("Delete", "A list is accessing an object (%p) already deleted (list name = %s)",
                   obj, GetName());
          else if (obj && obj->IsOnHeap())
@@ -350,7 +350,7 @@ void THashList::RecursiveRemove(TObject *obj)
    while (lnk.get()) {
       next = lnk->NextSP();
       TObject *ob = lnk->GetObject();
-      if (ob && ob->TestBit(kNotDeleted)) {
+      if (ob && !ROOT::Detail::HasBeenDeleted(ob)) {
          ob->RecursiveRemove(obj);
       }
       lnk = next;
diff --git a/core/cont/src/TList.cxx b/core/cont/src/TList.cxx
index 034c7be31adaf..3ce34a2b8bef2 100644
--- a/core/cont/src/TList.cxx
+++ b/core/cont/src/TList.cxx
@@ -440,12 +440,12 @@ void TList::Clear(Option_t *option)
       // delete only heap objects marked OK to clear
       auto obj = tlk->GetObject();
       if (!nodel && obj) {
-         if (!obj->TestBit(kNotDeleted)) {
+         if (ROOT::Detail::HasBeenDeleted(obj)) {
             Error("Clear", "A list is accessing an object (%p) already deleted (list name = %s)",
                   obj, GetName());
          } else if (obj->IsOnHeap()) {
             if (obj->TestBit(kCanDelete)) {
-               if (obj->TestBit(kNotDeleted)) {
+               if (!ROOT::Detail::HasBeenDeleted(obj)) {
                   TCollection::GarbageCollect(obj);
                }
             }
@@ -501,7 +501,7 @@ void TList::Delete(Option_t *option)
 
          // delete only heap objects
          auto obj = tlk->GetObject();
-         if (obj && !obj->TestBit(kNotDeleted))
+         if (obj && ROOT::Detail::HasBeenDeleted(obj))
             Error("Delete", "A list is accessing an object (%p) already deleted (list name = %s)",
                   obj, GetName());
          else if (obj && obj->IsOnHeap())
@@ -530,7 +530,7 @@ void TList::Delete(Option_t *option)
          // delete only heap objects
          auto obj = tlk->GetObject();
          tlk->SetObject(nullptr);
-         if (obj && !obj->TestBit(kNotDeleted))
+         if (obj && ROOT::Detail::HasBeenDeleted(obj))
             Error("Delete", "A list is accessing an object (%p) already deleted (list name = %s)",
                   obj, GetName());
          else if (obj && obj->IsOnHeap())
@@ -643,7 +643,7 @@ TObjLink *TList::FindLink(const TObject *obj, Int_t &idx) const
    while (lnk) {
       object = lnk->GetObject();
       if (object) {
-         if (object->TestBit(kNotDeleted)) {
+         if (!ROOT::Detail::HasBeenDeleted(object)) {
             if (object->IsEqual(obj)) return lnk;
          }
       }
@@ -773,7 +773,7 @@ void TList::RecursiveRemove(TObject *obj)
       auto cached = fCache.lock();
       if (cached && cached->fNext.get() == nullptr && cached->fPrev.lock().get() == nullptr) {
          TObject *ob = cached->GetObject();
-         if (ob && ob->TestBit(kNotDeleted)) {
+         if (ob && !ROOT::Detail::HasBeenDeleted(ob)) {
             ob->RecursiveRemove(obj);
          }
       }
@@ -787,7 +787,7 @@ void TList::RecursiveRemove(TObject *obj)
    while (lnk.get()) {
       next = lnk->fNext;
       TObject *ob = lnk->GetObject();
-      if (ob && ob->TestBit(kNotDeleted)) {
+      if (ob && !ROOT::Detail::HasBeenDeleted(ob)) {
          if (ob->IsEqual(obj)) {
             lnk->SetObject(nullptr);
             if (lnk == fFirst) {
diff --git a/core/cont/src/TObjArray.cxx b/core/cont/src/TObjArray.cxx
index ac02d217fdeca..3b531dbeba36c 100644
--- a/core/cont/src/TObjArray.cxx
+++ b/core/cont/src/TObjArray.cxx
@@ -675,7 +675,7 @@ void TObjArray::RecursiveRemove(TObject *obj)
    R__COLLECTION_WRITE_LOCKGUARD(ROOT::gCoreMutex);
 
    for (int i = 0; i < fSize; i++) {
-      if (fCont[i] && fCont[i]->TestBit(kNotDeleted) && fCont[i]->IsEqual(obj)) {
+      if (fCont[i] && !ROOT::Detail::HasBeenDeleted(fCont[i]) && fCont[i]->IsEqual(obj)) {
          fCont[i] = nullptr;
          // recalculate array size
          if (i == fLast)
@@ -683,7 +683,7 @@ void TObjArray::RecursiveRemove(TObject *obj)
                fLast--;
             } while (fLast >= 0 && !fCont[fLast]);
          Changed();
-      } else if (fCont[i] && fCont[i]->TestBit(kNotDeleted))
+      } else if (fCont[i] && !ROOT::Detail::HasBeenDeleted(fCont[i]))
          fCont[i]->RecursiveRemove(obj);
    }
 }
diff --git a/core/cont/src/TObjectTable.cxx b/core/cont/src/TObjectTable.cxx
index ed43ccb393e7a..e78f7f339cf98 100644
--- a/core/cont/src/TObjectTable.cxx
+++ b/core/cont/src/TObjectTable.cxx
@@ -383,7 +383,7 @@ void TObjectTable::UpdateInstCount() const
 
    for (int i = 0; i < fSize; i++)
       if ((op = fTable[i])) {                // attention: no ==
-         if (op->TestBit(TObject::kNotDeleted))
+         if (!ROOT::Detail::HasBeenDeleted(op))
             op->IsA()->AddInstance(op->IsOnHeap());
          else
             Error("UpdateInstCount", "oops 0x%zx\n", (size_t)op);
diff --git a/core/gui/src/TContextMenu.cxx b/core/gui/src/TContextMenu.cxx
index dc266ee6d2ab0..cf6f17742ced7 100644
--- a/core/gui/src/TContextMenu.cxx
+++ b/core/gui/src/TContextMenu.cxx
@@ -126,7 +126,7 @@ void TContextMenu::Action(TClassMenuItem *menuitem)
 
    if (object) {
       // If object deleted, remove from popup and return
-      if (!(object->TestBit(kNotDeleted))) {
+      if (ROOT::Detail::HasBeenDeleted(object)) {
          menuitem->SetType(TClassMenuItem::kPopupSeparator);
          menuitem->SetCall(nullptr, "");
          return;
diff --git a/etc/valgrind-root.supp b/etc/valgrind-root.supp
index 230362de38cc4..01ea89754559d 100644
--- a/etc/valgrind-root.supp
+++ b/etc/valgrind-root.supp
@@ -1013,6 +1013,14 @@
    fun:_ZN11TBufferFile13ReadStdStringERSs
 }
 
+######## ROOT use-after-delete detection attempts
+
+{
+   Checking if delete taints memory
+   Memcheck:Addr4
+   fun:_ZN4ROOT8Internal*DeleteChangesMemory*
+}
+
 ######## ROOT TObject on heap
 
 {
diff --git a/graf2d/gpad/src/TButton.cxx b/graf2d/gpad/src/TButton.cxx
index c768d018c2d26..d724956d1d386 100644
--- a/graf2d/gpad/src/TButton.cxx
+++ b/graf2d/gpad/src/TButton.cxx
@@ -149,7 +149,7 @@ void TButton::Draw(Option_t *option)
 void TButton::ExecuteEvent(Int_t event, Int_t px, Int_t py)
 {
    //check case where pressing a button deletes itself
-   if (!TestBit(kNotDeleted)) return;
+   if (ROOT::Detail::HasBeenDeleted(this)) return;
 
    if (IsEditable()) {
       TPad::ExecuteEvent(event,px,py);
@@ -202,7 +202,7 @@ void TButton::ExecuteEvent(Int_t event, Int_t px, Int_t py)
          gROOT->ProcessLine(GetMethod());
       }
       //check case where pressing a button deletes itself
-      if (!TestBit(kNotDeleted)) return;
+      if (ROOT::Detail::HasBeenDeleted(this)) return;
       SetBorderMode(1);
       Modified();
       Update();
diff --git a/graf2d/gpad/src/TCanvas.cxx b/graf2d/gpad/src/TCanvas.cxx
index 4f976b954a4c6..605e23a3926cf 100644
--- a/graf2d/gpad/src/TCanvas.cxx
+++ b/graf2d/gpad/src/TCanvas.cxx
@@ -687,7 +687,7 @@ void TCanvas::Destructor()
       if ((*gThreadXAR)("CDEL", 2, arr, 0)) return;
    }
 
-   if (!TestBit(kNotDeleted)) return;
+   if (ROOT::Detail::HasBeenDeleted(this)) return;
 
    SafeDelete(fContextMenu);
    if (!gPad) return;
diff --git a/graf2d/gpad/src/TPad.cxx b/graf2d/gpad/src/TPad.cxx
index ab8c1846e8e10..4d4db5996c93e 100644
--- a/graf2d/gpad/src/TPad.cxx
+++ b/graf2d/gpad/src/TPad.cxx
@@ -379,7 +379,7 @@ TPad::TPad(const char *name, const char *title, Double_t xlow,
 
 TPad::~TPad()
 {
-   if (!TestBit(kNotDeleted)) return;
+   if (ROOT::Detail::HasBeenDeleted(this)) return;
    Close();
    CloseToolTip(fTip);
    DeleteToolTip(fTip);
@@ -633,7 +633,7 @@ void TPad::Clear(Option_t *option)
       SafeDelete(fView);
       if (fPrimitives) fPrimitives->Clear(option);
       if (fFrame) {
-         if (fFrame->TestBit(kNotDeleted)) delete fFrame;
+         if (! ROOT::Detail::HasBeenDeleted(fFrame)) delete fFrame;
          fFrame = nullptr;
       }
    }
@@ -973,18 +973,18 @@ Int_t TPad::ClipPolygon(Int_t n, Double_t *x, Double_t *y, Int_t nn, Double_t *x
 
 void TPad::Close(Option_t *)
 {
-   if (!TestBit(kNotDeleted)) return;
+   if (ROOT::Detail::HasBeenDeleted(this)) return;
    if (!fMother) return;
-   if (!fMother->TestBit(kNotDeleted)) return;
+   if (ROOT::Detail::HasBeenDeleted(fMother)) return;
 
    if (fPrimitives)
       fPrimitives->Clear();
    if (fView) {
-      if (fView->TestBit(kNotDeleted)) delete fView;
+      if (!ROOT::Detail::HasBeenDeleted(fView)) delete fView;
       fView = nullptr;
    }
    if (fFrame) {
-      if (fFrame->TestBit(kNotDeleted)) delete fFrame;
+      if (!ROOT::Detail::HasBeenDeleted(fFrame)) delete fFrame;
       fFrame = nullptr;
    }
 
@@ -1274,7 +1274,7 @@ void TPad::Draw(Option_t *option)
    // pad cannot be in itself and it can only be in one other pad at a time
    if (!fPrimitives) fPrimitives = new TList;
    if (gPad != this) {
-      if (fMother && fMother->TestBit(kNotDeleted))
+      if (fMother && !ROOT::Detail::HasBeenDeleted(fMother))
             if (fMother->GetListOfPrimitives()) fMother->GetListOfPrimitives()->Remove(this);
       TPad *oldMother = fMother;
       fCanvas = gPad->GetCanvas();
@@ -4611,7 +4611,7 @@ TPad *TPad::Pick(Int_t px, Int_t py, TObjLink *&pickobj)
 void TPad::Pop()
 {
    if (!fMother) return;
-   if (!fMother->TestBit(kNotDeleted)) return;
+   if (ROOT::Detail::HasBeenDeleted(fMother)) return;
    if (!fPrimitives) fPrimitives = new TList;
    if (this == fMother->GetListOfPrimitives()->Last()) return;
 
diff --git a/graf2d/gpad/src/TRatioPlot.cxx b/graf2d/gpad/src/TRatioPlot.cxx
index 25967b2b3f147..1f6b911cc2e72 100644
--- a/graf2d/gpad/src/TRatioPlot.cxx
+++ b/graf2d/gpad/src/TRatioPlot.cxx
@@ -111,26 +111,31 @@ TRatioPlot::~TRatioPlot()
 
    gROOT->GetListOfCleanups()->Remove(this);
 
-   if (fRatioGraph && fRatioGraph->TestBit(kNotDeleted)) delete fRatioGraph;
-   if (fConfidenceInterval1 && fConfidenceInterval1->TestBit(kNotDeleted)) delete fConfidenceInterval1;
-   if (fConfidenceInterval2 && fConfidenceInterval2->TestBit(kNotDeleted)) delete fConfidenceInterval2;
+   auto safeDelete = [](TObject *obj) {
+      if (obj && !ROOT::Detail::HasBeenDeleted(obj))
+         delete obj;
+   };
+
+   safeDelete(fRatioGraph);
+   safeDelete(fConfidenceInterval1);
+   safeDelete(fConfidenceInterval2);
 
    for (unsigned int i=0;i<fGridlines.size();++i) {
       delete (fGridlines[i]);
    }
 
-   if (fSharedXAxis && fSharedXAxis->TestBit(kNotDeleted)) delete fSharedXAxis;
-   if (fUpperGXaxis && fUpperGXaxis->TestBit(kNotDeleted)) delete fUpperGXaxis;
-   if (fLowerGXaxis && fLowerGXaxis->TestBit(kNotDeleted)) delete fLowerGXaxis;
-   if (fUpperGYaxis && fUpperGYaxis->TestBit(kNotDeleted)) delete fUpperGYaxis;
-   if (fLowerGYaxis && fLowerGYaxis->TestBit(kNotDeleted)) delete fLowerGYaxis;
-   if (fUpperGXaxisMirror && fUpperGXaxisMirror->TestBit(kNotDeleted)) delete fUpperGXaxisMirror;
-   if (fLowerGXaxisMirror && fLowerGXaxisMirror->TestBit(kNotDeleted)) delete fLowerGXaxisMirror;
-   if (fUpperGYaxisMirror && fUpperGYaxisMirror->TestBit(kNotDeleted)) delete fUpperGYaxisMirror;
-   if (fLowerGYaxisMirror && fLowerGYaxisMirror->TestBit(kNotDeleted)) delete fLowerGYaxisMirror;
+   safeDelete(fSharedXAxis);
+   safeDelete(fUpperGXaxis);
+   safeDelete(fLowerGXaxis);
+   safeDelete(fUpperGYaxis);
+   safeDelete(fLowerGYaxis);
+   safeDelete(fUpperGXaxisMirror);
+   safeDelete(fLowerGXaxisMirror);
+   safeDelete(fUpperGYaxisMirror);
+   safeDelete(fLowerGYaxisMirror);
 
-   if (fUpYaxis && fUpYaxis->TestBit(kNotDeleted)) delete fUpYaxis;
-   if (fLowYaxis && fLowYaxis->TestBit(kNotDeleted)) delete fLowYaxis;
+   safeDelete(fUpYaxis);
+   safeDelete(fLowYaxis);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/graf2d/graf/src/TPaveText.cxx b/graf2d/graf/src/TPaveText.cxx
index aa9f24e71d2ba..708a7db84bf7a 100644
--- a/graf2d/graf/src/TPaveText.cxx
+++ b/graf2d/graf/src/TPaveText.cxx
@@ -115,7 +115,7 @@ TPaveText::TPaveText(Double_t x1, Double_t y1,Double_t x2, Double_t  y2, Option_
 
 TPaveText::~TPaveText()
 {
-   if (!TestBit(kNotDeleted)) return;
+   if (ROOT::Detail::HasBeenDeleted(this)) return;
    if (fLines) fLines->Delete();
    delete fLines;
    fLines = nullptr;
diff --git a/graf3d/g3d/src/TGeometry.cxx b/graf3d/g3d/src/TGeometry.cxx
index 5355c2b53e76c..b4b02e7adb0e9 100644
--- a/graf3d/g3d/src/TGeometry.cxx
+++ b/graf3d/g3d/src/TGeometry.cxx
@@ -346,7 +346,7 @@ TNode *TGeometry::GetNode(const char *name) const
 {
    TNode *node= (TNode*)GetListOfNodes()->First();
    if (!node) return 0;
-   if (node->TestBit(kNotDeleted))  return node->GetNode(name);
+   if (!ROOT::Detail::HasBeenDeleted(node))  return node->GetNode(name);
    return 0;
 }
 
diff --git a/graf3d/g3d/src/TNode.cxx b/graf3d/g3d/src/TNode.cxx
index 92a72dc1f7e91..ace9ebce38aa1 100644
--- a/graf3d/g3d/src/TNode.cxx
+++ b/graf3d/g3d/src/TNode.cxx
@@ -382,7 +382,7 @@ TNode *TNode::GetNode(const char *name) const
    TObjLink *lnk = fNodes->FirstLink();
    while (lnk) {
       node = (TNode *)lnk->GetObject();
-      if (node->TestBit(kNotDeleted)) {
+      if (!ROOT::Detail::HasBeenDeleted(node)) {
          nodefound = node->GetNode(name);
          if (nodefound) return nodefound;
       }
diff --git a/gui/gui/src/TGFileBrowser.cxx b/gui/gui/src/TGFileBrowser.cxx
index 8f049e88e703a..225863f118be4 100644
--- a/gui/gui/src/TGFileBrowser.cxx
+++ b/gui/gui/src/TGFileBrowser.cxx
@@ -656,7 +656,7 @@ void TGFileBrowser::Update()
    TGListTreeItem *curr = fListTree->GetSelected(); // GetCurrent() ??
    if (curr) {
       TObject *obj = (TObject *) curr->GetUserData();
-      if (obj && !obj->TestBit(kNotDeleted)) {
+      if (obj && ROOT::Detail::HasBeenDeleted(obj)) {
          // if the item to be deleted has a filter,
          // delete its entry in the map
          if (CheckFiltered(curr))
@@ -665,7 +665,7 @@ void TGFileBrowser::Update()
          curr = 0;
          obj = 0;
       }
-      else if (obj && obj->TestBit(kNotDeleted) &&
+      else if (obj && !ROOT::Detail::HasBeenDeleted(obj) &&
                obj->InheritsFrom("TObjString") && curr->GetParent()) {
          fListTree->GetPathnameFromItem(curr->GetParent(), path);
          if (strlen(path) > 1) {
diff --git a/gui/gui/src/TGFrame.cxx b/gui/gui/src/TGFrame.cxx
index dadbb6d2bb2b4..1ad1940f3c6b6 100644
--- a/gui/gui/src/TGFrame.cxx
+++ b/gui/gui/src/TGFrame.cxx
@@ -1731,7 +1731,7 @@ Bool_t TGMainFrame::HandleClientMessage(Event_t *event)
    if ((event->fFormat == 32) && ((Atom_t)event->fUser[0] == gWM_DELETE_WINDOW) &&
        (event->fHandle != gROOT_MESSAGE)) {
       Emit("CloseWindow()");
-      if (TestBit(kNotDeleted) && !TestBit(kDontCallClose))
+      if (!ROOT::Detail::HasBeenDeleted(this) && !TestBit(kDontCallClose))
          CloseWindow();
    }
    return kTRUE;
diff --git a/gui/gui/src/TGMdiMainFrame.cxx b/gui/gui/src/TGMdiMainFrame.cxx
index b6609603f30e4..96a6bc669846e 100644
--- a/gui/gui/src/TGMdiMainFrame.cxx
+++ b/gui/gui/src/TGMdiMainFrame.cxx
@@ -963,7 +963,7 @@ Int_t TGMdiMainFrame::Close(TGMdiFrame *mdiframe)
    TGMdiDecorFrame *frame = GetDecorFrame(mdiframe);
    Restore(mdiframe);
    mdiframe->Emit("CloseWindow()");
-   if (frame && mdiframe->TestBit(kNotDeleted) && !mdiframe->TestBit(TGMdiFrame::kDontCallClose))
+   if (frame && !ROOT::Detail::HasBeenDeleted(mdiframe) && !mdiframe->TestBit(TGMdiFrame::kDontCallClose))
       return frame->CloseWindow();
    return kTRUE;
 }
diff --git a/gui/gui/src/TGTextEntry.cxx b/gui/gui/src/TGTextEntry.cxx
index c71f713cd73eb..f51c6cd419575 100644
--- a/gui/gui/src/TGTextEntry.cxx
+++ b/gui/gui/src/TGTextEntry.cxx
@@ -1229,7 +1229,7 @@ Bool_t TGTextEntry::HandleKey(Event_t* event)
    if ((EKeySym)keysym  == kKey_Enter || (EKeySym)keysym  == kKey_Return) {
 
       ReturnPressed();                                      // emit signal
-      if (!TestBit(kNotDeleted)) return kTRUE;
+      if (ROOT::Detail::HasBeenDeleted(this)) return kTRUE;
       fSelectionOn = kFALSE;
 
    } else if (event->fState & kKeyShiftMask && (EKeySym)keysym  == kKey_Backtab) {
diff --git a/hist/hist/src/TEfficiency.cxx b/hist/hist/src/TEfficiency.cxx
index e0132c8bab955..2a7002de3d69e 100644
--- a/hist/hist/src/TEfficiency.cxx
+++ b/hist/hist/src/TEfficiency.cxx
@@ -1033,7 +1033,7 @@ TEfficiency::~TEfficiency()
       TObject* obj = 0;
       while ((obj  = fFunctions->First())) {
          while(fFunctions->Remove(obj)) { }
-         if (!obj->TestBit(kNotDeleted)) {
+         if (ROOT::Detail::HasBeenDeleted(obj)) {
             break;
          }
          delete obj;
diff --git a/hist/hist/src/TH1.cxx b/hist/hist/src/TH1.cxx
index 8257ceccd9798..dfa759d744ba2 100644
--- a/hist/hist/src/TH1.cxx
+++ b/hist/hist/src/TH1.cxx
@@ -623,7 +623,7 @@ TH1::TH1(): TNamed(), TAttLine(), TAttFill(), TAttMarker()
 
 TH1::~TH1()
 {
-   if (!TestBit(kNotDeleted)) {
+   if (ROOT::Detail::HasBeenDeleted(this)) {
       return;
    }
    delete[] fIntegral;
@@ -644,7 +644,7 @@ TH1::~TH1()
       //and may have been already deleted.
       while ((obj  = fFunctions->First())) {
          while(fFunctions->Remove(obj)) { }
-         if (!obj->TestBit(kNotDeleted)) {
+         if (ROOT::Detail::HasBeenDeleted(obj)) {
             break;
          }
          delete obj;
diff --git a/net/net/src/TApplicationServer.cxx b/net/net/src/TApplicationServer.cxx
index ea59b3fc80079..bcd8c9693c105 100644
--- a/net/net/src/TApplicationServer.cxx
+++ b/net/net/src/TApplicationServer.cxx
@@ -896,7 +896,7 @@ Int_t TApplicationServer::SendCanvases()
       while (lnk) {
          TObject *sc = lnk->GetObject();
          lnk = lnk->Next();
-         if ((sc->TestBit(kNotDeleted)) && sc == o)
+         if ((!ROOT::Detail::HasBeenDeleted(sc)) && sc == o)
             sentalready = kTRUE;
       }
       if (!sentalready) {
diff --git a/tutorials/net/spyserv.C b/tutorials/net/spyserv.C
index 53e8a2ea68eb6..587f1f41a4757 100644
--- a/tutorials/net/spyserv.C
+++ b/tutorials/net/spyserv.C
@@ -133,7 +133,7 @@ SpyServ::SpyServ()
          TSocket *s;
          if ((s = fMon->Select(20)) != (TSocket*)-1)
             HandleSocket(s);
-         if (!fCanvas->TestBit(TObject::kNotDeleted))
+         if (ROOT::Detail::HasBeenDeleted(fCanvas))
             break;
          if (gROOT->IsInterrupted())
             break;