Dllimport函數返回結構

Question

我有第三方.dll，我必須在C++/CLI代碼中使用它的函數。我想dllimport的，但我收到一個錯誤：

錯誤C33385：「msp_FormatMessage」：具有dllimport的定製attribite不能返回類

的一個實例，在C＃中這個問題可以通過解決的功能使用StructLayout，但我找不到在C++/CLI中解決此問題的任何方法。

函數定義：

[DllImport("drtl3.dll", EntryPoint = "msp_FormatMessage")] 
extern "C++" msp_Message msp_FormatMessage(msp_Message* buffer, char type, char RT, char SA, char RTR_MC, unsigned short SAR_MCD, char dataWordCount, unsigned short data[], unsigned int bccw); 

結構定義：

typedef struct { 
     msp_WORD type; 
     msp_WORD dataWordCount; 
     msp_WORD bccw; 
     msp_WORD CmdWord1; 
     msp_WORD CmdWord2; 
     msp_WORD Data[32]; 
     msp_WORD StatusWord1; 
     msp_WORD StatusWord2; 
     msp_WORD loopback; 
     msp_WORD bsw; 
     msp_WORD timetag; 
     msp_BYTE present; 
     msp_BYTE transmit; 
     msp_BYTE check; 
     msp_BYTE role; 
} msp_Message; 

Answer 1

不明白的問題..顯示的代碼。顯示錯誤消息..我剛剛測試了dllimport的結構..

您應該注意，通過dlopen和dlsym或loadlibrary和getprocaddress的動態加載通常是首選。爲什麼？因爲你不能「總是」dllimport。例如：使用VS2012的dllexport並不總是在g ++中使用dllimport。關於如何導出符號沒有定義的標準。

使用的MinGW-G ++ 4.8.1

DLL：

#include <windows.h> 
#include <cstring> 

typedef struct { 
    unsigned short meh; 
    unsigned short bleh; 
    char we[50]; 
} foo; 

extern __declspec(dllexport) foo some_func() 
{ 
    foo f; 
    f.meh = 10; 
    f.bleh = 20; 
    strcpy(f.we, "hello world\0"); 
    return f; 
} 

extern "C" __declspec(dllexport) BOOL APIENTRY DllMain(HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpvReserved) 
{ 
    switch (fdwReason) 
    { 
     case DLL_PROCESS_ATTACH: 
      break; 

     case DLL_PROCESS_DETACH: 
      break; 
    } 
    return TRUE; 
} 

進口商：

#include <iostream> 

typedef struct { 
    unsigned short meh; 
    unsigned short bleh; 
    char we[50]; 
} foo; 

extern __declspec(dllimport) foo some_func(); 

int main() 
{ 
    foo f = some_func(); 

    std::cout<<f.meh<<" "<<f.bleh<<" "<<f.we<<"\n"; 
    return 0; 
} 

結果：10 20 hello world

Answer 2

你需要聲明它返回作爲非託管結構，這將工作得很好：

#using <mscorlib.dll> 
using namespace System::Runtime::InteropServices; 

#pragma managed(push, off) 
using msp_WORD = short; 
using msp_BYTE = char; 
typedef struct { 
    msp_WORD type; 
    msp_WORD dataWordCount; 
    msp_WORD bccw; 
    msp_WORD CmdWord1; 
    msp_WORD CmdWord2; 
    msp_WORD Data[32]; 
    msp_WORD StatusWord1; 
    msp_WORD StatusWord2; 
    msp_WORD loopback; 
    msp_WORD bsw; 
    msp_WORD timetag; 
    msp_BYTE present; 
    msp_BYTE transmit; 
    msp_BYTE check; 
    msp_BYTE role; 
} msp_Message; 
#pragma managed(pop) 

[DllImport("drtl3.dll", EntryPoint = "msp_FormatMessage")] 
extern "C++" msp_Message msp_FormatMessage(msp_Message* buffer, char type, char RT, char SA, char RTR_MC, unsigned short SAR_MCD, char dataWordCount, unsigned short data [], unsigned int bccw); 

或者如果不工作，你永遠可以做到這一點的C++方式也適用於C++/CLI有點

#include "windows.h" 
#pragma managed(push, off) 
using msp_WORD = short; 
using msp_BYTE = char; 
typedef struct { 
    msp_WORD type; 
    msp_WORD dataWordCount; 
    msp_WORD bccw; 
    msp_WORD CmdWord1; 
    msp_WORD CmdWord2; 
    msp_WORD Data[32]; 
    msp_WORD StatusWord1; 
    msp_WORD StatusWord2; 
    msp_WORD loopback; 
    msp_WORD bsw; 
    msp_WORD timetag; 
    msp_BYTE present; 
    msp_BYTE transmit; 
    msp_BYTE check; 
    msp_BYTE role; 
} msp_Message; 
#pragma managed(pop) 

typedef msp_Message msp_FormatMessage_t(msp_Message* buffer, char type, char RT, char SA, char RTR_MC, unsigned short SAR_MCD, char dataWordCount, unsigned short data [], unsigned int bccw); 

msp_FormatMessage_t *msp_FormatMessage; 
HINSTANCE hDLL; 

int main(array<System::String ^> ^args) 
{ 
    hDLL= LoadLibraryA("drtl3.dll"); 
    msp_FormatMessage = (msp_FormatMessage_t *)GetProcAddress(hDLL,"?msp_FormatMessage@@YA?AUmsp_Message_t@@PAU1@DDDDGDQAGI@Z"); 
    msp_Message test = msp_FormatMessage(nullptr, 1, 2, 3, 4, 5, 6, nullptr, 7); 
    Console::Write("type "); 
    Console::WriteLine(test.type); 
    Console::Write("check"); 
    Console::WriteLine(test.check); 

    // std::cout << "type" << test.type << std::endl; 
    //std::cout << "check" << test.check << std::endl; 

    Console::WriteLine(L"Hello World"); 
    return 0; 
} 

名稱?msp_FormatMessage@@YA?AUmsp_Message_t@@PAU1@DDDDGDQAGI@Z是，你可以通過在運行DUMPBIN /EXPORTS drtl3.dll得到什麼visual studio命令行。也可能只是C鏈接，這會使名稱更小。