diff --git a/graph/Graph.cc b/graph/Graph.cc
index 3ce7aec6..cf9b0438 100644
--- a/graph/Graph.cc
+++ b/graph/Graph.cc
@@ -657,7 +657,7 @@ Graph::makePrevPaths(Vertex *vertex,
 }
 
 PathVertexRep *
-Graph::prevPaths(Vertex *vertex) const
+Graph::prevPaths(Vertex *vertex)
 {
   return prev_paths_.pointer(vertex->prevPaths());
 }
diff --git a/include/sta/ArrayTable.hh b/include/sta/ArrayTable.hh
index 16fdafce..67fb78da 100644
--- a/include/sta/ArrayTable.hh
+++ b/include/sta/ArrayTable.hh
@@ -47,8 +47,8 @@ public:
                uint32_t count);
   // Grow as necessary and return pointer for id.
   TYPE *ensureId(ObjectId id);
-  TYPE *pointer(ObjectId id) const;
-  TYPE &ref(ObjectId id) const;
+  TYPE *pointer(ObjectId id);
+  TYPE &ref(ObjectId id);
   size_t size() const { return size_; }
   void clear();
 
@@ -58,7 +58,7 @@ public:
 
 private:
   ArrayBlock<TYPE> *makeBlock(uint32_t size);
-  void pushBlock(ArrayBlock<TYPE> *block);
+  void pushBlock(size_t size);
   void deleteBlocks();
 
   size_t size_;
@@ -66,11 +66,8 @@ private:
   BlockIdx free_block_idx_;
   // Index of next free object in free_block_idx_.
   ObjectIdx free_idx_;
-  // Don't use std::vector so growing blocks_ can be thread safe.
-  size_t blocks_size_;
-  size_t blocks_capacity_;
-  ArrayBlock<TYPE>* *blocks_;
-  ArrayBlock<TYPE>* *prev_blocks_;
+  std::vector<ArrayBlock<TYPE>> blocks_;
+  std::vector<ArrayBlock<TYPE>> prev_blocks_;
   // Linked list of free arrays indexed by array size.
   std::vector<ObjectId> free_list_;
   static constexpr ObjectId idx_mask_ = block_size - 1;
@@ -80,28 +77,24 @@ template <class TYPE>
 ArrayTable<TYPE>::ArrayTable() :
   size_(0),
   free_block_idx_(block_idx_null),
-  free_idx_(object_idx_null),
-  blocks_size_(0),
-  blocks_capacity_(1024),
-  blocks_(new ArrayBlock<TYPE>*[blocks_capacity_]),
-  prev_blocks_(nullptr)
+  free_idx_(object_idx_null)
 {
+  blocks_.reserve(1024);
 }
 
 template <class TYPE>
 ArrayTable<TYPE>::~ArrayTable()
 {
   deleteBlocks();
-  delete [] blocks_;
-  delete [] prev_blocks_;
 }
 
 template <class TYPE>
 void
 ArrayTable<TYPE>::deleteBlocks()
 {
-  for (size_t i = 0; i < blocks_size_; i++)
-    delete blocks_[i];
+  for (size_t i = 0; i < blocks_.size(); i++)
+    blocks_[i].free();
+  blocks_.clear();
 }
 
 template <class TYPE>
@@ -120,12 +113,12 @@ ArrayTable<TYPE>::make(uint32_t count,
     free_list_[count] = *head;
   }
   else {
-    ArrayBlock<TYPE> *block = blocks_size_ ? blocks_[free_block_idx_] : nullptr;
+    ArrayBlock<TYPE> *block = blocks_.size() ? &blocks_[free_block_idx_] : nullptr;
     if ((free_idx_ == object_idx_null
          && free_block_idx_ == block_idx_null)
         || free_idx_ + count >= block->size()) {
       uint32_t size = block_size;
-      if (blocks_size_ == 0
+      if (blocks_.size() == 0
           // First block starts at idx 1.
           && count > block_size - 1)
         size = count + 1;
@@ -145,32 +138,36 @@ template <class TYPE>
 ArrayBlock<TYPE> *
 ArrayTable<TYPE>::makeBlock(uint32_t size)
 {
-  BlockIdx block_idx = blocks_size_;
-  ArrayBlock<TYPE> *block = new ArrayBlock<TYPE>(size);
-  pushBlock(block); 
+  BlockIdx block_idx = blocks_.size();
+  pushBlock(size);
   free_block_idx_ = block_idx;
   // ObjectId zero is reserved for object_id_null.
   free_idx_ = (block_idx > 0) ? 0 : 1;
-  return block;
+  return &blocks_[block_idx];
 }
 
 template <class TYPE>
 void
-ArrayTable<TYPE>::pushBlock(ArrayBlock<TYPE> *block)
+ArrayTable<TYPE>::pushBlock(size_t size)
 {
-  blocks_[blocks_size_++] = block;
-  if (blocks_size_ >= block_id_max)
+  blocks_.push_back(ArrayBlock<TYPE>(size));
+
+  if (blocks_.size() >= block_id_max)
     criticalError(223, "max array table block count exceeded.");
-  if (blocks_size_ == blocks_capacity_) {
-    size_t new_capacity = blocks_capacity_ * 1.5;
-    ArrayBlock<TYPE>** new_blocks = new ArrayBlock<TYPE>*[new_capacity];
-    memcpy(new_blocks, blocks_, blocks_capacity_ * sizeof(ArrayBlock<TYPE>*));
-    if (prev_blocks_)
-      delete [] prev_blocks_;
+  if (blocks_.size() == blocks_.capacity()) {
+    prev_blocks_.reserve(blocks_.capacity() * 1.5);
+    const auto blocks_mid = blocks_.begin() + prev_blocks_.size();
+    std::copy(blocks_.begin(), blocks_mid, prev_blocks_.begin());
+    prev_blocks_.insert(prev_blocks_.end(), blocks_mid, blocks_.end());
     // Preserve block array for other threads to reference.
-    prev_blocks_ = blocks_;
-    blocks_ = new_blocks;
-    blocks_capacity_ = new_capacity;
+    // Swap the vectors while keeping blocks_ valid.
+    // vector::swap is usually basically the same,
+    // but a naive implementation might temporarily set blocks_ to null.
+    const size_t vec_size = sizeof(blocks_);
+    std::uint8_t tmp[vec_size];
+    std::memcpy(&tmp, static_cast<void*>(&blocks_), vec_size);
+    std::memcpy(static_cast<void*>(&blocks_), static_cast<void*>(&prev_blocks_), vec_size);
+    std::memcpy(static_cast<void*>(&prev_blocks_), &tmp, vec_size);
   }
 }
 
@@ -191,14 +188,14 @@ ArrayTable<TYPE>::destroy(ObjectId id,
 
 template <class TYPE>
 TYPE *
-ArrayTable<TYPE>::pointer(ObjectId id) const
+ArrayTable<TYPE>::pointer(ObjectId id)
 {
   if (id == object_id_null)
     return nullptr;
   else {
     BlockIdx blk_idx = id >> idx_bits;
     ObjectIdx obj_idx = id & idx_mask_;
-    return blocks_[blk_idx]->pointer(obj_idx);
+    return blocks_[blk_idx].pointer(obj_idx);
   }
 }
 
@@ -209,23 +206,22 @@ ArrayTable<TYPE>::ensureId(ObjectId id)
   BlockIdx blk_idx = id >> idx_bits;
   ObjectIdx obj_idx = id & idx_mask_;
   // Make enough blocks for blk_idx to be valid.
-  for (BlockIdx i = blocks_size_; i <= blk_idx; i++) {
-    ArrayBlock<TYPE> *block = new ArrayBlock<TYPE>(block_size);
-    pushBlock(block);
+  for (BlockIdx i = blocks_.size(); i <= blk_idx; i++) {
+    pushBlock(block_size);
   }
-  return blocks_[blk_idx]->pointer(obj_idx);
+  return blocks_[blk_idx].pointer(obj_idx);
 }
 
 template <class TYPE>
 TYPE &
-ArrayTable<TYPE>::ref(ObjectId id) const
+ArrayTable<TYPE>::ref(ObjectId id)
 {
   if (id == object_id_null)
     criticalError(222, "null ObjectId reference is undefined.");
 
   BlockIdx blk_idx = id >> idx_bits;
   ObjectIdx obj_idx = id & idx_mask_;
-  return blocks_[blk_idx]->ref(obj_idx);
+  return blocks_[blk_idx].ref(obj_idx);
 }
 
 template <class TYPE>
@@ -233,7 +229,6 @@ void
 ArrayTable<TYPE>::clear()
 {
   deleteBlocks();
-  blocks_size_ = 0;
   size_ = 0;
   free_block_idx_ = block_idx_null;
   free_idx_ = object_idx_null;
@@ -246,11 +241,12 @@ template <class TYPE>
 class ArrayBlock
 {
 public:
+  ArrayBlock() = default;
   ArrayBlock(uint32_t size);
-  ~ArrayBlock();
   uint32_t size() const { return size_; }
   TYPE &ref(ObjectIdx idx) { return objects_[idx]; }
   TYPE *pointer(ObjectIdx idx) { return &objects_[idx]; }
+  void free() { delete[] objects_; }
 
 private:
   uint32_t size_;
@@ -264,10 +260,4 @@ ArrayBlock<TYPE>::ArrayBlock(uint32_t size) :
 {
 }
 
-template <class TYPE>
-ArrayBlock<TYPE>::~ArrayBlock()
-{
-  delete [] objects_;
-}
-
 } // Namespace
diff --git a/include/sta/Graph.hh b/include/sta/Graph.hh
index 593e0f2f..d025470c 100644
--- a/include/sta/Graph.hh
+++ b/include/sta/Graph.hh
@@ -113,7 +113,7 @@ public:
   size_t requiredCount() const { return requireds_.size(); }
   PathVertexRep *makePrevPaths(Vertex *vertex,
 			       uint32_t count);
-  PathVertexRep *prevPaths(Vertex *vertex) const;
+  PathVertexRep *prevPaths(Vertex *vertex);
   void clearPrevPaths();
   // Reported slew are the same as those in the liberty tables.
   //  reported_slews = measured_slews / slew_derate_from_library