我在DLL中有一个结构，到目前为止，该结构仅在该DLL中使用过。
我想通过指针在另一个DLL中使用该结构。因此，我在结构定义中添加了__declspec(dllexport)。简单地添加该dll导出语句现在会导致该结构无法编译（不仅仅是常规的DLL导出警告）。这是我第一次看到这种行为。我正在使用Visual Studio2019。我不知道潜在的问题是什么。
仅将'__declspec（dllexport）'添加到struct / class会使编译失败的原因是什么？
struct __declspec(dllexport) PipelineManager {
// ...
private:
std::unordered_map<std::string, std::string> mPathToName;
std::unordered_map<std::string, vko::PipelineLayout> mLayouts;
std::unordered_map<std::string, vko::GraphicsPipeline> mPipelines;
std::unordered_map<std::string, std::unique_ptr<GraphicsPipelineDef>> mDefs;
};
以下大部分错误：
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\VC\Tools\MSVC\14.21.27619\include\xmemory0(820,1): error C2280: 'std::pair<const _Kty,_Ty>::pair(const std::pair<const _Kty,_Ty> &)': attempting to reference a deleted function
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\VC\Tools\MSVC\14.21.27619\include\xmemory0(820,1): error C2280: with
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\VC\Tools\MSVC\14.21.27619\include\xmemory0(820,1): error C2280: [
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\VC\Tools\MSVC\14.21.27619\include\xmemory0(820,1): error C2280: _Kty=std::string,
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\VC\Tools\MSVC\14.21.27619\include\xmemory0(820,1): error C2280: _Ty=std::unique_ptr<ngen::rendo::GraphicsPipelineDef,std::default_delete<ngen::rendo::GraphicsPipelineDef>>
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\VC\Tools\MSVC\14.21.27619\include\xmemory0(820,1): error C2280: ] (compiling source file Z:\NGEN\Source\Renderer\GpuProgramManager.cpp)
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\VC\Tools\MSVC\14.21.27619\include\utility(133): message : see declaration of 'std::pair<const _Kty,_Ty>::pair'
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\VC\Tools\MSVC\14.21.27619\include\utility(133): message : with
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\VC\Tools\MSVC\14.21.27619\include\utility(133): message : [
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\VC\Tools\MSVC\14.21.27619\include\utility(133): message : _Kty=std::string,
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\VC\Tools\MSVC\14.21.27619\include\utility(133): message : _Ty=std::unique_ptr<ngen::rendo::GraphicsPipelineDef,std::default_delete<ngen::rendo::GraphicsPipelineDef>>
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\VC\Tools\MSVC\14.21.27619\include\utility(133): message : ] (compiling source file Z:\NGEN\Source\Renderer\GpuProgramManager.cpp)
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\VC\Tools\MSVC\14.21.27619\include\utility(133,5): message : 'std::pair<const _Kty,_Ty>::pair(const std::pair<const _Kty,_Ty> &)': function was implicitly deleted because a data member invokes a deleted or inaccessible function 'std::unique_ptr<ngen::rendo::GraphicsPipelineDef,std::default_delete<_Ty>>::unique_ptr(const std::unique_ptr<_Ty,std::default_delete<_Ty>> &)'
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\VC\Tools\MSVC\14.21.27619\include\utility(133,5): message : with
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\VC\Tools\MSVC\14.21.27619\include\utility(133,5): message : [
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\VC\Tools\MSVC\14.21.27619\include\utility(133,5): message : _Kty=std::string,
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\VC\Tools\MSVC\14.21.27619\include\utility(133,5): message : _Ty=std::unique_ptr<ngen::rendo::GraphicsPipelineDef,std::default_delete<ngen::rendo::GraphicsPipelineDef>>
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\VC\Tools\MSVC\14.21.27619\include\utility(133,5): message : ]
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\VC\Tools\MSVC\14.21.27619\include\utility(133,5): message : and
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\VC\Tools\MSVC\14.21.27619\include\utility(133,5): message : [
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\VC\Tools\MSVC\14.21.27619\include\utility(133,5): message : _Ty=ngen::rendo::GraphicsPipelineDef
1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Preview\VC\Tools\MSVC\14.21.27619\include\utility(133,5): message : ] (compiling source file Z:\NGEN\Source\Renderer\GpuProgramManager.cpp)
// ...
1>Z:\NGEN\Source\Renderer/PipelineManager.hpp(67): message : see reference to function template instantiation 'std::unordered_map<std::string,std::unique_ptr<ngen::rendo::GraphicsPipelineDef,std::default_delete<_Ty>>,std::hash<_Kty>,std::equal_to<_Kty>,std::allocator<std::pair<const _Kty,std::unique_ptr<_Ty,std::default_delete<_Ty>>>>>::unordered_map(const std::unordered_map<_Kty,std::unique_ptr<_Ty,std::default_delete<_Ty>>,std::hash<_Kty>,std::equal_to<_Kty>,std::allocator<std::pair<const _Kty,std::unique_ptr<_Ty,std::default_delete<_Ty>>>>> &)' being compiled
1>Z:\NGEN\Source\Renderer/PipelineManager.hpp(67): message : with
1>Z:\NGEN\Source\Renderer/PipelineManager.hpp(67): message : [
1>Z:\NGEN\Source\Renderer/PipelineManager.hpp(67): message : _Ty=ngen::rendo::GraphicsPipelineDef,
1>Z:\NGEN\Source\Renderer/PipelineManager.hpp(67): message : _Kty=std::string
1>Z:\NGEN\Source\Renderer/PipelineManager.hpp(67): message : ] (compiling source file Z:\NGEN\Source\Renderer\GpuVM.cpp)
1>Z:\NGEN\Source\Renderer/PipelineManager.hpp(66): message : see reference to class template instantiation 'std::unordered_map<std::string,std::unique_ptr<ngen::rendo::GraphicsPipelineDef,std::default_delete<_Ty>>,std::hash<_Kty>,std::equal_to<_Kty>,std::allocator<std::pair<const _Kty,std::unique_ptr<_Ty,std::default_delete<_Ty>>>>>' being compiled
1>Z:\NGEN\Source\Renderer/PipelineManager.hpp(66): message : with
1>Z:\NGEN\Source\Renderer/PipelineManager.hpp(66): message : [
1>Z:\NGEN\Source\Renderer/PipelineManager.hpp(66): message : _Ty=ngen::rendo::GraphicsPipelineDef,
1>Z:\NGEN\Source\Renderer/PipelineManager.hpp(66): message : _Kty=std::string
1>Z:\NGEN\Source\Renderer/PipelineManager.hpp(66): message : ] (compiling source file Z:\NGEN\Source\Renderer\GpuVM.cpp)