C ++消费delphi DLL [英] C++ consuming delphi DLL

问题描述

我无法使用在delphi中开发的dll的功能。我对类型的转换有些困难。

I'm not able to use the function of a dll developed in delphi. I'm having some difficulties with the conversions of types.

这是我要调用DLL的函数：

This is the function I want to call the DLL:

function rData(ID: Cardinal; queue: WideString): WideString; stdcall;

我在C ++中的代码是：

My code in C++ was so:

typedef string (*ReturnDataSPL)(DWORD, string);

string result;
HMODULE hLib;
hLib = LoadLibrary("delphi.dll");
pReturnDataSPL = (ReturnDataSPL)GetProcAddress(hLib,"rData");
if (NULL != pReturnDataSPL)
   result = pReturnDataSPL(JobID,printerName);

问题我无法使它工作。我不知道哪种类型与Delphi WideString和Cardinal兼容。

The problem I'm not able to make it work. I do not know which type is compatible with Delphi WideString and Cardinal.

有人帮我

EDIT：

这是我要调用DLL的函数：

This is the function I want to call the DLL:

procedure rData(ID: Cardinal; queue: WideString; var Result: WideString); stdcall;

更改后的代码如下：

typedef void (__stdcall *ReturnDataSPL)(DWORD, BSTR, BSTR&);

HMODULE hLib;
BSTR result = NULL;
hLib = LoadLibrary("delphi.dll");

pReturnDataSPL = (ReturnDataSPL)GetProcAddress(hLib,"rData");
if (NULL != pReturnDataSPL)
{
   pReturnDataSPL(JobID,(BSTR)"Lexmark X656de (MS) (Copiar 2)",result);
}

推荐答案

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为了开始您当前的代码不能希望成功，因为我假设 string 是 std :: string 。这是Delphi代码不能提供或消费的C ++数据类型。要匹配Delphi的 WideString ，您需要使用COM BSTR 数据类型。

For a start your current code can't hope to succeed since I presume string is std::string. That's a C++ data type which Delphi code cannot either provide or consume. To match up against Delphi's WideString you need to use the COM BSTR data type.

您的代码的另一个问题是它在C ++端使用 cdecl ，而 stdcall 在Delphi端。您将需要调整调用约定。

Another problem with your code as it stands is that it uses cdecl in the C++ side, and stdcall on the Delphi side. You'll need to align the calling conventions.

但是，这也将失败，因为Delphi的ABI返回值和平台标准之间的差异。该主题在此详细讨论：为什么不能将WideString用作interop的函数返回值？

However, that will also fail because of a difference between Delphi's ABI for return values, and the platform standard. That topic was covered in detail here: Why can a WideString not be used as a function return value for interop?

最好的办法是停止使用 WideString 作为返回值，并将其转换为C ++参考参数。

Your best bet is to stop using WideString as a return value and convert it into a C++ reference parameter. You'll want to convert the Delphi to match.

您正在查找类似如下的内容：

You are looking at something like this:

strong> Delphi

Delphi

procedure rData(ID: Cardinal; queue: WideString; var Result: WideString); stdcall;

C ++

typedef void (__stdcall *ReturnDataSPL)(DWORD, BSTR, BSTR&);

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