fix util::stack_vector

src/util/stack_vector.hpp

@@ -5,20 +5,30 @@
 namespace util {
     template<typename T, int capacity>
     class stack_vector {
+        struct buffer {
+            alignas(alignof(T)) char* data[sizeof(T) * capacity];
+
+            T* ptr() {
+                return reinterpret_cast<T*>(data);
+            }
+            const T* ptr() const {
+                return reinterpret_cast<const T*>(data);
+            }
+        };
     public:
         stack_vector() : size_(0) {}
 
         stack_vector(const stack_vector<T, capacity>& other)
             : size_(other.size_) {
             for (int i = 0; i < size_; ++i) {
-                new (&data_[i]) T(other.data_[i]);
+                new (&data_.ptr()[i]) T(other.data_.ptr()[i]);
             }
         }
 
         stack_vector(stack_vector<T, capacity>&& other) noexcept
             : size_(other.size_) {
             for (int i = 0; i < size_; ++i) {
-                new (&data_[i]) T(std::move(other.data_[i]));
+                new (&data_.ptr()[i]) T(std::move(other.data_.ptr()[i]));
             }
             other.size_ = 0;
         }
@@ -29,17 +39,25 @@ namespace util {
                 "initializer list exceeds stack vector capacity"
             );
             for (const auto& value : init) {
-                new (&data_[size_++]) T(value);
+                new (&data_.ptr()[size_++]) T(value);
             }
         }
 
-        ~stack_vector() {
-            clear();
-        }
+        ~stack_vector() = default;
 
         void push_back(const T& value) {
             if (size_ < capacity) {
-                data_[size_++] = value;
+                auto data = reinterpret_cast<char*>(data_.ptr() + (size_++));
+                new (data) T(value);
+            } else {
+                throw std::overflow_error("stack vector capacity exceeded");
+            }
+        }
+
+        void push_back(T&& value) {
+            if (size_ < capacity) {
+                auto data = reinterpret_cast<char*>(data_.ptr() + (size_++));
+                new (data) T(std::move(value));
             } else {
                 throw std::overflow_error("stack vector capacity exceeded");
             }
@@ -47,7 +65,7 @@ namespace util {
 
         void pop_back() {
             if (size_ > 0) {
-                data_[size_ - 1].~T();
+                data_.ptr()[size_ - 1].~T();
                 --size_;
             } else {
                 throw std::underflow_error("stack vector is empty");
@@ -56,31 +74,31 @@ namespace util {
 
         void clear() {
             for (int i = 0; i < size_; ++i) {
-                data_[i].~T();
+                data_.ptr()[i].~T();
             }
             size_ = 0;
         }
 
         T& operator[](int index) {
-            return data_[index];
+            return data_.ptr()[index];
         }
         
         const T& operator[](int index) const {
-            return data_[index];
+            return data_.ptr()[index];
         }
 
         T& at(int index) {
             if (index < 0 || index >= size_) {
                 throw std::out_of_range("index out of range");
             }
-            return data_[index];
+            return data_.ptr()[index];
         }
 
         const T& at(int index) const {
             if (index < 0 || index >= size_) {
                 throw std::out_of_range("index out of range");
             }
-            return data_[index];
+            return data_.ptr()[index];
         }
 
         int size() const { 
@@ -96,22 +114,22 @@ namespace util {
         }
 
         auto begin() {
-            return data_;
+            return data_.ptr();
         }
 
         auto end() {
-            return data_ + size_;
+            return data_.ptr() + size_;
         }
 
         auto begin() const {
-            return data_;
+            return data_.ptr();
         }
 
         auto end() const {
-            return data_ + size_;
+            return data_.ptr() + size_;
         }
     private:
-        T data_[capacity];
+        buffer data_;
         int size_;
     };
 }

test/util/stack_vector.cpp

@@ -0,0 +1,20 @@
+#include <gtest/gtest.h>
+#include <string>
+
+#include "util/stack_vector.hpp"
+
+using namespace util;
+
+TEST(util, stack_vector) {
+    stack_vector<std::string, 4> vec;
+    vec.push_back("hello");
+    vec.push_back("world");
+    vec.push_back("?");
+    ASSERT_EQ(3, vec.size());
+    vec.pop_back();
+    ASSERT_EQ(2, vec.size());
+    vec.clear();
+    ASSERT_EQ(0, vec.size());
+    ASSERT_TRUE(vec.empty());
+    vec.push_back("test");
+}