diff --git a/include/libimp/codecvt.h b/include/libimp/codecvt.h
index 1107a0a..09931dd 100644
--- a/include/libimp/codecvt.h
+++ b/include/libimp/codecvt.h
@@ -1,7 +1,7 @@
 /**
  * \file libimp/codecvt.h
  * \author mutouyun (orz@orzz.org)
- * \brief Character set conversion interface
+ * \brief Character set conversion interface.
  * \date 2022-08-07
  */
 #pragma once
diff --git a/include/libimp/countof.h b/include/libimp/countof.h
index 9298f8d..72df251 100644
--- a/include/libimp/countof.h
+++ b/include/libimp/countof.h
@@ -1,7 +1,7 @@
 /**
  * \file libimp/countof.h
  * \author mutouyun (orz@orzz.org)
- * \brief Returns the size of the given range
+ * \brief Returns the size of the given range.
  * \date 2022-03-01
  */
 #pragma once
diff --git a/include/libimp/dataof.h b/include/libimp/dataof.h
index a49bd36..de19f62 100644
--- a/include/libimp/dataof.h
+++ b/include/libimp/dataof.h
@@ -1,7 +1,7 @@
 /**
  * \file libimp/dataof.h
  * \author mutouyun (orz@orzz.org)
- * \brief Returns the data pointer of the given range
+ * \brief Returns the data pointer of the given range.
  * \date 2023-05-27
  */
 #pragma once
diff --git a/include/libimp/export.h b/include/libimp/export.h
index 6ba509c..f12d452 100644
--- a/include/libimp/export.h
+++ b/include/libimp/export.h
@@ -1,7 +1,7 @@
 /**
  * \file libimp/export.h
  * \author mutouyun (orz@orzz.org)
- * \brief Define the symbol export interfaces
+ * \brief Define the symbol export interfaces.
  * \date 2022-02-27
  */
 #pragma once
diff --git a/include/libimp/pimpl.h b/include/libimp/pimpl.h
index d0b0b2b..990d0de 100644
--- a/include/libimp/pimpl.h
+++ b/include/libimp/pimpl.h
@@ -1,7 +1,7 @@
 /**
  * \file libimp/pimpl.h
  * \author mutouyun (orz@orzz.org)
- * \brief Pointer To Implementation (pImpl) idiom
+ * \brief Pointer To Implementation (pImpl) idiom.
  * \date 2022-02-27
  */
 #pragma once
diff --git a/include/libimp/result.h b/include/libimp/result.h
index 3960f88..a859b9f 100644
--- a/include/libimp/result.h
+++ b/include/libimp/result.h
@@ -1,7 +1,7 @@
 /**
  * \file libimp/result.h
  * \author mutouyun (orz@orzz.org)
- * \brief Define the return value type with a status code
+ * \brief Define the return value type with a status code.
  * \date 2022-04-17
  */
 #pragma once
diff --git a/include/libimp/scope_exit.h b/include/libimp/scope_exit.h
new file mode 100644
index 0000000..66e341f
--- /dev/null
+++ b/include/libimp/scope_exit.h
@@ -0,0 +1,78 @@
+/**
+ * \file libimp/scope_exit.h
+ * \author mutouyun (orz@orzz.org)
+ * \brief Execute guard function when the enclosing scope exits.
+ * \date 2022-03-01
+ */
+#pragma once
+
+#include <utility>    // std::forward, std::move
+#include <functional> // std::function
+#include <type_traits>
+
+#include "libimp/def.h"
+
+LIBIMP_NAMESPACE_BEG_
+
+template <typename F = std::function<void()>>
+class scope_exit {
+  F destructor_;
+  mutable bool released_;
+
+public:
+  template <typename G>
+  explicit scope_exit(G &&destructor) noexcept
+    : destructor_(std::forward<G>(destructor))
+    , released_  (false) {}
+
+  scope_exit(scope_exit &&other) noexcept
+    : destructor_(std::move(other.destructor_))
+    , released_  (std::exchange(other.released_, true)) /*release rhs*/ {}
+
+  scope_exit &operator=(scope_exit &&other) noexcept {
+    destructor_ = std::move(other.destructor_);
+    released_   = std::exchange(other.released_, true);
+    return *this;
+  }
+
+  ~scope_exit() noexcept {
+    if (!released_) destructor_();
+  }
+
+  void release() const noexcept {
+    released_ = true;
+  }
+
+  void do_exit() noexcept {
+    if (released_) return;
+    destructor_();
+    released_ = true;
+  }
+
+  void swap(scope_exit &other) noexcept {
+    std::swap(destructor_, other.destructor_);
+    std::swap(released_  , other.released_);
+  }
+};
+
+/// \brief Creates a scope_exit object.
+template <typename F>
+auto make_scope_exit(F &&destructor) noexcept {
+  return scope_exit<std::decay_t<F>>(std::forward<F>(destructor));
+}
+
+namespace detail {
+
+struct scope_exit_helper {
+  template <typename F>
+  auto operator=(F &&f) const noexcept {
+    return make_scope_exit(std::forward<F>(f));
+  }
+};
+
+} // namespace detail
+
+#define LIBIMP_SCOPE_EXIT($val) \
+  auto $val = ::LIBIMP::detail::scope_exit_helper{}
+
+LIBIMP_NAMESPACE_END_
diff --git a/include/libimp/span.h b/include/libimp/span.h
index c05f79b..fe94284 100644
--- a/include/libimp/span.h
+++ b/include/libimp/span.h
@@ -1,7 +1,7 @@
 /**
  * \file libimp/span.h
  * \author mutouyun (orz@orzz.org)
- * \brief Describes an object that can refer to a contiguous sequence of objects
+ * \brief Describes an object that can refer to a contiguous sequence of objects.
  * \date 2022-10-16
  */
 #pragma once
diff --git a/include/libimp/system.h b/include/libimp/system.h
index aed8d7c..3517ed7 100644
--- a/include/libimp/system.h
+++ b/include/libimp/system.h
@@ -1,7 +1,7 @@
 /**
  * \file libimp/system.h
  * \author mutouyun (orz@orzz.org)
- * \brief Isolation and encapsulation of system APIs
+ * \brief Isolation and encapsulation of system APIs.
  * \date 2022-08-07
  */
 #pragma once
diff --git a/include/libimp/underlyof.h b/include/libimp/underlyof.h
index edef44f..0fa4ace 100644
--- a/include/libimp/underlyof.h
+++ b/include/libimp/underlyof.h
@@ -1,7 +1,7 @@
 /**
  * \file libimp/underlyof.h
  * \author mutouyun (orz@orzz.org)
- * \brief Returns the underlying type of the given enum
+ * \brief Returns the underlying type of the given enum.
  * \date 2022-03-01
  */
 #pragma once
diff --git a/include/libpmr/small_storage.h b/include/libpmr/small_storage.h
index 068bab9..9406a3c 100644
--- a/include/libpmr/small_storage.h
+++ b/include/libpmr/small_storage.h
@@ -223,6 +223,39 @@ void *holder_construct(allocator const &alloc, std::size_t n, Construct &&c) {
   }
 }
 
+class holder_info_ptr {
+  allocator const &alloc_;
+  holder_info **pptr_;
+
+public:
+  holder_info_ptr(allocator const &alloc, holder_info *(&ptr)) noexcept
+    : alloc_(alloc), pptr_(&ptr) {
+    *pptr_ = static_cast<holder_info *>(alloc_.allocate(sizeof(holder_info), alignof(holder_info)));
+  }
+
+  ~holder_info_ptr() noexcept {
+    if (pptr_ == nullptr) return;
+    alloc_.deallocate(*pptr_, sizeof(holder_info), alignof(holder_info));
+    *pptr_ = nullptr;
+  }
+
+  explicit operator bool() const noexcept {
+    return (pptr_ != nullptr) && (*pptr_ != nullptr);
+  }
+
+  holder_info *operator->() const noexcept {
+    return *pptr_;
+  }
+
+  holder_info &operator*() noexcept {
+    return **pptr_;
+  }
+
+  void release() noexcept {
+    pptr_ = nullptr;
+  }
+};
+
 } // namespace detail
 
 /**
@@ -246,7 +279,7 @@ public:
             std::enable_if_t<alignof(Value) <= alignof(std::max_align_t), bool> = true>
   holder(allocator const &alloc, ::LIBIMP::types<Value>, std::size_t n) : holder() {
     value_ptr_ = detail::holder_construct<Value>(alloc, n, 
-      ::LIBIMP::uninitialized_default_construct_n<Value *, std::size_t>);
+        ::LIBIMP::uninitialized_default_construct_n<Value *, std::size_t>);
     if (value_ptr_ == nullptr) return;
     info_.type = &typeid(Value);
     info_.sizeof_type = sizeof(Value);
@@ -271,6 +304,7 @@ public:
   }
 
   std::type_info const &type() const noexcept override {
+    if (!valid()) return typeid(nullptr);
     return *info_.type;
   }
 
@@ -314,4 +348,104 @@ public:
   }
 };
 
+/**
+ * \class template <> holder<void, false>
+ * \brief A holder implementation of some data objects that stores type information on heap memory.
+ */
+template <>
+class holder<void, false> : public holder_base {
+
+  detail::holder_info *info_ptr_;
+  void *value_ptr_;
+
+public:
+  holder() noexcept
+    : info_ptr_ (nullptr)
+    , value_ptr_(nullptr) {}
+
+  /// \brief Constructs a holder with type of `Value`.
+  /// alignof(Value) must be less than or equal to alignof(std::max_align_t).
+  template <typename Value, 
+            std::enable_if_t<alignof(Value) <= alignof(std::max_align_t), bool> = true>
+  holder(allocator const &alloc, ::LIBIMP::types<Value>, std::size_t n) : holder() {
+    detail::holder_info_ptr info_p{alloc, info_ptr_};
+    if (!info_p) return;
+    value_ptr_ = detail::holder_construct<Value>(alloc, n, 
+        ::LIBIMP::uninitialized_default_construct_n<Value *, std::size_t>);
+    if (value_ptr_ == nullptr) return;
+    info_p->type = &typeid(Value);
+    info_p->sizeof_type = sizeof(Value);
+    info_p->count = n;
+    info_p->copy = [](allocator const &alloc, void const *s, void *d) {
+      auto const &src = *static_cast<holder const *>(s);
+      auto &      dst = *::LIBIMP::construct<holder>(d);
+      if (!src.valid()) return;
+      detail::holder_info_ptr info_p{alloc, dst.info_ptr_};
+      if (!info_p) return;
+      dst.value_ptr_ = detail::holder_construct<Value>(alloc, src.count(), [s = src.get()](Value *d, std::size_t n) {
+        std::uninitialized_copy_n(static_cast<Value const *>(s), n, d);
+      });
+      if (dst.value_ptr_ == nullptr) return;
+      *info_p = *src.info_ptr_;
+      info_p.release();
+    };
+    info_p->dest = [](void *p, std::size_t n) noexcept {
+      ::LIBIMP::destroy_n(static_cast<Value *>(p), n);
+    };
+    info_p.release();
+  }
+
+  bool valid() const noexcept override {
+    return (value_ptr_ != nullptr) && (info_ptr_ != nullptr);
+  }
+
+  std::type_info const &type() const noexcept override {
+    if (!valid()) return typeid(nullptr);
+    return *info_ptr_->type;
+  }
+
+  std::size_t sizeof_type() const noexcept override {
+    if (!valid()) return 0;
+    return info_ptr_->sizeof_type;
+  }
+
+  std::size_t sizeof_heap() const noexcept override {
+    if (!valid()) return 0;
+    return info_ptr_->sizeof_type * info_ptr_->count + sizeof(detail::holder_info);
+  }
+
+  std::size_t count() const noexcept override {
+    if (!valid()) return 0;
+    return info_ptr_->count;
+  }
+
+  void *get() noexcept override {
+    return value_ptr_;
+  }
+
+  void const *get() const noexcept override {
+    return value_ptr_;
+  }
+
+  void move_to(allocator const &, void *p) noexcept override {
+    auto *des = ::LIBIMP::construct<holder>(p);
+    if (!valid()) return;
+    std::swap(value_ptr_, des->value_ptr_);
+    std::swap(info_ptr_ , des->info_ptr_);
+  }
+
+  void copy_to(allocator const &alloc, void *p) const noexcept(false) override {
+    auto *des = ::LIBIMP::construct<holder>(p);
+    if (!valid()) return;
+    info_ptr_->copy(alloc, this, des);
+  }
+
+  void destroy(allocator const &alloc) noexcept override {
+    if (!valid()) return;
+    info_ptr_->dest (value_ptr_, count());
+    alloc.deallocate(value_ptr_, sizeof_heap());
+    alloc.deallocate(info_ptr_ , sizeof(detail::holder_info), alignof(detail::holder_info));
+  }
+};
+
 LIBPMR_NAMESPACE_END_
diff --git a/test/pmr/test_pmr_small_storage.cpp b/test/pmr/test_pmr_small_storage.cpp
index 6b5e1d9..6300f64 100644
--- a/test/pmr/test_pmr_small_storage.cpp
+++ b/test/pmr/test_pmr_small_storage.cpp
@@ -11,6 +11,7 @@ TEST(small_storage, holder_construct) {
   pmr::holder<int, true>();
   pmr::holder<int, false>();
   pmr::holder<void, true>();
+  pmr::holder<void, false>();
   SUCCEED();
 }
 
@@ -19,21 +20,25 @@ TEST(small_storage, holder_copy_move_construct) {
   EXPECT_FALSE((std::is_copy_constructible<pmr::holder<int, true>>::value));
   EXPECT_FALSE((std::is_copy_constructible<pmr::holder<int, false>>::value));
   EXPECT_FALSE((std::is_copy_constructible<pmr::holder<void, true>>::value));
+  EXPECT_FALSE((std::is_copy_constructible<pmr::holder<void, false>>::value));
 
   EXPECT_FALSE(std::is_copy_assignable<pmr::holder_null>::value);
   EXPECT_FALSE((std::is_copy_assignable<pmr::holder<int, true>>::value));
   EXPECT_FALSE((std::is_copy_assignable<pmr::holder<int, false>>::value));
   EXPECT_FALSE((std::is_copy_assignable<pmr::holder<void, true>>::value));
+  EXPECT_FALSE((std::is_copy_assignable<pmr::holder<void, false>>::value));
 
   EXPECT_FALSE(std::is_move_constructible<pmr::holder_null>::value);
   EXPECT_FALSE((std::is_move_constructible<pmr::holder<int, true>>::value));
   EXPECT_FALSE((std::is_move_constructible<pmr::holder<int, false>>::value));
   EXPECT_FALSE((std::is_move_constructible<pmr::holder<void, true>>::value));
+  EXPECT_FALSE((std::is_move_constructible<pmr::holder<void, false>>::value));
 
   EXPECT_FALSE(std::is_move_assignable<pmr::holder_null>::value);
   EXPECT_FALSE((std::is_move_assignable<pmr::holder<int, true>>::value));
   EXPECT_FALSE((std::is_move_assignable<pmr::holder<int, false>>::value));
   EXPECT_FALSE((std::is_move_assignable<pmr::holder<void, true>>::value));
+  EXPECT_FALSE((std::is_move_assignable<pmr::holder<void, false>>::value));
 }
 
 TEST(small_storage, holder_copy_move) {
@@ -46,7 +51,7 @@ TEST(small_storage, holder_copy_move) {
 
   pmr::allocator alc;
   pmr::holder<foo, true> h1(alc, 1);
-  pmr::holder<foo, true> h2, h3; // uninitialized
+  pmr::holder<foo, true> h2, h3;
   h1.copy_to(alc, &h2);
   EXPECT_EQ(static_cast<foo *>(h1.get())->i, 1);
   EXPECT_EQ(static_cast<foo *>(h2.get())->i, 1);
@@ -58,7 +63,7 @@ TEST(small_storage, holder_copy_move) {
   h3.destroy(alc);
 
   pmr::holder<foo, false> h4(alc, 1);
-  pmr::holder<foo, false> h5, h6; // uninitialized
+  pmr::holder<foo, false> h5, h6;
   h4.copy_to(alc, &h5);
   EXPECT_EQ(static_cast<foo *>(h4.get())->i, 1);
   EXPECT_EQ(static_cast<foo *>(h5.get())->i, 1);
@@ -70,7 +75,7 @@ TEST(small_storage, holder_copy_move) {
   h6.destroy(alc);
 
   pmr::holder<void, true> h7(alc, ::LIBIMP::types<int>{}, 10);
-  pmr::holder<void, true> h8, h9; // uninitialized
+  pmr::holder<void, true> h8, h9;
   h7.copy_to(alc, &h8);
   EXPECT_EQ(h7.count(), 10);
   EXPECT_EQ(h8.count(), 10);
@@ -80,6 +85,18 @@ TEST(small_storage, holder_copy_move) {
   h7.destroy(alc);
   h8.destroy(alc);
   h9.destroy(alc);
+
+  pmr::holder<void, false> h10(alc, ::LIBIMP::types<int>{}, 10);
+  pmr::holder<void, false> h11, h12;
+  h10.copy_to(alc, &h11);
+  EXPECT_EQ(h10.count(), 10);
+  EXPECT_EQ(h11.count(), 10);
+  h10.move_to(alc, &h12);
+  EXPECT_EQ(h10.count(), 0);
+  EXPECT_EQ(h12.count(), 10);
+  h10.destroy(alc);
+  h11.destroy(alc);
+  h12.destroy(alc);
 }
 
 TEST(small_storage, construct) {