Avoid subtracting it.control() and table.control() in single element table during erase.

`it.control()` is pointing to `kSooControl` global buffer. The result of subtraction is not used, but that causes UBSAN pointer overflow error.

PiperOrigin-RevId: 758683515
Change-Id: Ifa9e3f7f2da3de371dd65f3e1d42c77c20aece59

Author: goldvitaly

absl/container/internal/raw_hash_set.cc

@@ -526,9 +526,8 @@ ABSL_ATTRIBUTE_ALWAYS_INLINE inline void InitializeThreeElementsControlBytes(
 
 }  // namespace
 
-void EraseMetaOnly(CommonFields& c, size_t index, size_t slot_size) {
-  ABSL_SWISSTABLE_ASSERT(IsFull(c.control()[index]) &&
-                         "erasing a dangling iterator");
+void EraseMetaOnly(CommonFields& c, const ctrl_t* ctrl, size_t slot_size) {
+  ABSL_SWISSTABLE_ASSERT(IsFull(*ctrl) && "erasing a dangling iterator");
   c.decrement_size();
   c.infoz().RecordErase();
 
@@ -538,6 +537,8 @@ void EraseMetaOnly(CommonFields& c, size_t index, size_t slot_size) {
     return;
   }
 
+  size_t index = static_cast<size_t>(ctrl - c.control());
+
   if (WasNeverFull(c, index)) {
     SetCtrl(c, index, ctrl_t::kEmpty, slot_size);
     c.growth_info().OverwriteFullAsEmpty();

absl/container/internal/raw_hash_set.h

@@ -1847,7 +1847,7 @@ void ClearBackingArray(CommonFields& c, const PolicyFunctions& policy,
                        void* alloc, bool reuse, bool soo_enabled);
 
 // Type-erased version of raw_hash_set::erase_meta_only.
-void EraseMetaOnly(CommonFields& c, size_t index, size_t slot_size);
+void EraseMetaOnly(CommonFields& c, const ctrl_t* ctrl, size_t slot_size);
 
 // For trivially relocatable types we use memcpy directly. This allows us to
 // share the same function body for raw_hash_set instantiations that have the
@@ -3140,8 +3140,7 @@ class raw_hash_set {
       common().set_empty_soo();
       return;
     }
-    EraseMetaOnly(common(), static_cast<size_t>(it.control() - control()),
-                  sizeof(slot_type));
+    EraseMetaOnly(common(), it.control(), sizeof(slot_type));
   }
 
   template <class K>
@@ -3691,8 +3690,7 @@ struct HashtableFreeFunctionsAccess {
           auto* slot = static_cast<SlotType*>(slot_void);
           if (pred(Set::PolicyTraits::element(slot))) {
             c->destroy(slot);
-            EraseMetaOnly(c->common(), static_cast<size_t>(ctrl - c->control()),
-                          sizeof(*slot));
+            EraseMetaOnly(c->common(), ctrl, sizeof(*slot));
             ++num_deleted;
           }
         });