使用std::vector创建vk::raii::ImageView触发默认构造函数删除错误

我尝试通过以下函数将std::vector<VkImage>映射为std::vector<vk::raii::ImageView>，实现参考了官方示例，但编译时出错，提示vk::raii::ImageView的默认构造函数已被删除。确认错误由这段代码导致，想知道这是vulkan_raii.hpp的问题，还是应该改用非RAII版本创建ImageView？

代码实现 #

std::vector<vk::raii::ImageView> Render::createImageViews(
    std::vector<VkImage>& images,
    vk::raii::Device& device
) {
    std::vector<vk::raii::ImageView> views(images.size());

    vk::ImageViewCreateInfo createInfo(
        {},
        {},
        vk::ImageViewType::e2D,
        vk::Format::eB8G8R8A8Srgb,
        {},
        { vk::ImageAspectFlagBits::eColor, 0, 1, 0, 1 }
    );

    for (size_t i = 0; i < images.size(); i++) {
        createInfo.image = images[i];
        views[i] = std::move(
            vk::raii::ImageView(device, createInfo)
        );
    }

    return views;
}

编译错误信息 #

make RUN=1
mkdir -p build/debug/obj
g++ -c -std=c++17 -Wall -pedantic -g -D ENABLE_VK_VALIDATION_LAYERS -D ENABLE_DEBUG_LOG -D VULKAN_HPP_NO_SMART_HANDLE -D VULKAN_HPP_NO_SPACESHIP_OPERATOR -D VULKAN_HPP_NO_TO_STRING -D VULKAN_HPP_NO_SETTERS src/render.cpp -o build/debug/obj/render.o
In file included from /usr/include/c++/11/optional:44,
                 from src/render.hpp:3,
                 from src/render.cpp:1:
/usr/include/c++/11/bits/stl_construct.h: In instantiation of ‘void std::_Construct(_Tp*, _Args&& ...) [with _Tp = vk::raii::ImageView; _Args = {}]’:
/usr/include/c++/11/bits/stl_uninitialized.h:579:18:   required from ‘static _ForwardIterator std::__uninitialized_default_n_1<_TrivialValueType>::__uninit_default_n(_ForwardIterator, _Size) [with _ForwardIterator = vk::raii::ImageView*; _Size = long unsigned int; bool _TrivialValueType = false]’
/usr/include/c++/11/bits/stl_uninitialized.h:640:20:   required from ‘_ForwardIterator std::__uninitialized_default_n(_ForwardIterator, _Size) [with _ForwardIterator = vk::raii::ImageView*; _Size = long unsigned int]’
/usr/include/c++/11/bits/stl_uninitialized.h:704:44:   required from ‘_ForwardIterator std::__uninitialized_default_n_a(_ForwardIterator, _Size, std::allocator<_Tp>&) [with _ForwardIterator = vk::raii::ImageView*; _Size = long unsigned int; _Tp = vk::raii::ImageView]’
/usr/include/c++/11/bits/stl_vector.h:1606:36:   required from ‘void std::vector<_Tp, _Alloc>::_M_default_initialize(std::vector<_Tp, _Alloc>::size_type) [with _Tp = vk::raii::ImageView; _Alloc = std::allocator<vk::raii::ImageView>; std::vector<_Tp, _Alloc>::size_type = long unsigned int]’
/usr/include/c++/11/bits/stl_vector.h:512:9:   required from ‘std::vector<_Tp, _Alloc>::vector(std::vector<_Tp, _Alloc>::size_type, const allocator_type&) [with _Tp = vk::raii::ImageView; _Alloc = std::allocator<vk::raii::ImageView>; std::vector<_Tp, _Alloc>::size_type = long unsigned int; std::vector<_Tp, _Alloc>::allocator_type = std::allocator<vk::raii::ImageView>]’
src/render.cpp:121:57:   required from here
/usr/include/c++/11/bits/stl_construct.h:119:7: error: use of deleted function ‘vk::raii::ImageView::ImageView()’
  119 |       ::new(static_cast<void*>(__p)) _Tp(std::forward<_Args>(__args)...);
      |       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from src/render.hpp:12,
                 from src/render.cpp:1:
/usr/include/vulkan/vulkan_raii.hpp:7501:7: note: declared here
 7501 |       ImageView()                    = delete;
      |       ^~~~~~~~~
make: *** [Makefile:44: build/debug/obj/render.o] Error 1

问题原因与解决方法 #

原因 #

报错核心是：std::vector<vk::raii::ImageView> views(images.size());这行代码会创建一个包含images.size()个元素的向量，而vector的这种构造方式会尝试默认构造每个元素。但vk::raii::ImageView作为RAII类，其默认构造函数被显式删除（设计上不允许存在无资源的空对象），因此编译失败。

解决方法 #

完全不需要改用非RAII版本，RAII是Vulkan官方推荐的资源管理方式，能自动释放资源避免泄漏。只需修改vector的初始化和元素添加方式：

优化后的代码

std::vector<vk::raii::ImageView> Render::createImageViews(
    std::vector<VkImage>& images,
    vk::raii::Device& device
) {
    std::vector<vk::raii::ImageView> views;
    views.reserve(images.size()); // 预分配空间，避免多次扩容

    vk::ImageViewCreateInfo createInfo(
        {},
        {},
        vk::ImageViewType::e2D,
        vk::Format::eB8G8R8A8Srgb,
        {},
        { vk::ImageAspectFlagBits::eColor, 0, 1, 0, 1 }
    );

    for (auto& image : images) {
        createInfo.image = image;
        views.emplace_back(device, createInfo); // 直接在vector内存中构造对象
    }

    return views;
}

关键改动说明 #

1. 初始化空vector，避免触发默认构造
2. 用reserve预分配足够空间，提升性能
3. 用emplace_back直接在vector的内存区域构造vk::raii::ImageView，跳过默认构造步骤

关于官方示例的疑问 #

官方示例大概率是用了emplace_back或直接在构造vector时填充元素，而非先创建指定大小的vector再赋值，因此不会触发默认构造。

内容的提问来源于stack exchange，提问作者Artsiom Miksiuk