C++/CLI、DllExport 和 /clr:pure

Question

这是一个简单的原生 DLL：

Native.h：

#ifdef BUILDING_NATIVE_DLL
#define DLLAPI __declspec(dllexport)
#else
#define DLLAPI __declspec(dllimport)
#endif

class DLLAPI Native
{
    public: void f();
};

Native.cpp：

#include "Native.h"

void Native::f()
{
}

构建：

cl /DBUILDING_NATIVE_DLL /LD Native.cpp
...
    Creating library Native.lib and object Native.exp

现在我想从 C++/CLI 应用程序中使用它：

Managed.cpp：

#include "Native.h"

int main()
{
    Native* native = new Native();
    native->f();
}

我可以在CLR模式“IJW”下构建它：

cl /clr Managed.cpp Native.lib
...

/out:Managed.exe
Managed.obj
Native.lib

但不是在 CLR 模式“纯”：

cl /clr:pure Managed.cpp Native.lib
Microsoft (R) C/C++ Optimizing Compiler Version 16.00.40219.01
for Microsoft (R) .NET Framework version 4.00.30319.18047
Copyright (C) Microsoft Corporation.  All rights reserved.

Managed.cpp
c:\users\...\Native.h(9) : warning C42
72: 'Native::f' : is marked __declspec(dllimport); must specify native calling c
onvention when importing a function.
c:\users\...\Native.h(10) : warning C4
272: 'Native::Native' : is marked __declspec(dllimport); must specify native cal
ling convention when importing a function.
c:\users\...\Native.h(10) : warning C4
272: 'Native::~Native' : is marked __declspec(dllimport); must specify native ca
lling convention when importing a function.
c:\users\...\Native.h(10) : warning C4
272: 'Native::Native' : is marked __declspec(dllimport); must specify native cal
ling convention when importing a function.
c:\users\...\Native.h(10) : warning C4
272: 'Native::operator =' : is marked __declspec(dllimport); must specify native
 calling convention when importing a function.
Microsoft (R) Incremental Linker Version 10.00.40219.01
Copyright (C) Microsoft Corporation.  All rights reserved.

/out:Managed.exe
/clrimagetype:pure
Managed.obj
Native.lib
Managed.obj : error LNK2028: unresolved token (0A000009) "public: void __clrcall
 Native::f(void)" (?f@Native@@$$FQAMXXZ) referenced in function "int __clrcall m
ain(void)" (?main@@$$HYMHXZ)
Managed.obj : error LNK2019: unresolved external symbol "public: void __clrcall
Native::f(void)" (?f@Native@@$$FQAMXXZ) referenced in function "int __clrcall ma
in(void)" (?main@@$$HYMHXZ)
Managed.exe : fatal error LNK1120: 2 unresolved externals

因此，似乎破坏构建的是缺少原生调用约定。

确实，如果我指定它：

#ifdef BUILDING_NATIVE_DLL
#define DLLAPI __declspec(dllexport)
#else
#define DLLAPI __declspec(dllimport)
#endif

class DLLAPI Native
{
    public: void __thiscall f();
};

这样更好：

cl /clr:pure Managed.cpp
Native.lib
Microsoft (R) C/C++ Optimizing Compiler Version 16.00.40219.01
for Microsoft (R) .NET Framework version 4.00.30319.18047
Copyright (C) Microsoft Corporation.  All rights reserved.

Managed.cpp
c:\users\...\Native.h(10) : warning C4
272: 'Native::Native' : is marked __declspec(dllimport); must specify native cal
ling convention when importing a function.
c:\users\...\Native.h(10) : warning C4
272: 'Native::~Native' : is marked __declspec(dllimport); must specify native ca
lling convention when importing a function.
c:\users\...\Native.h(10) : warning C4
272: 'Native::Native' : is marked __declspec(dllimport); must specify native cal
ling convention when importing a function.
c:\users\...\Native.h(10) : warning C4
272: 'Native::operator =' : is marked __declspec(dllimport); must specify native
 calling convention when importing a function.
Microsoft (R) Incremental Linker Version 10.00.40219.01
Copyright (C) Microsoft Corporation.  All rights reserved.

/out:Managed.exe
/clrimagetype:pure
Managed.obj
Native.lib

但仍然对生成的成员发出警告。

以下是问题：

• 是否可以为整个类指定调用约定，生成的成员将从该类继承？
• 如果头文件没有指定调用约定，如果不能修改，如何在CLR模式“纯”下构建？

谢谢。

Answer 1

尝试将本机头文件的#include 括起来

#pragma managed(push, off)
#include "Native.h"
#pragma managed(pop)

显然/clr:pure 编译单元不能有非托管的定义函数，但这些只是导入的声明——它应该可以工作。

但总体而言，不建议导出整个类。导出工厂函数并将其用于类构造，然后返回指向接口（具有纯虚拟成员的基类）的指针并将其用于成员访问，会更安全。这就是 COM 所做的，并且该技术在语言和编译器版本之间非常兼容。