C / C++ / MFC

16-Feb-09 5:28

Hi.
I'm new in c/c++... and I'm a little confused...
I made a dll in c/c++ (using some example I saw on-line), and now I want to load it in a new project, but it doesn't work.
I paste the dll file in the project debug folder, and I'm using
HINSTANCE myDll = LoadLibrary((LPCWSTR)"TestingDll.dll");

to access to it, but myDll is always empty...Can anyone tell me what possible I'm doing wrong?
Thanks

Taran916-Feb-09 6:03

Taran9

16-Feb-09 6:03

All the various dlls that TestingDll.dll is dependent on wuould not be present.
Check out the dependencies of TestingDll.dll using depends.exe and paste all those dlls also in the same folder.

Member Ártemis16-Feb-09 7:09

16-Feb-09 7:09

Thanks for your atention...
At the beginning I thought that was the problem and decided to do something very basic for testings, but I still can not access to it.
For my testings I made:

//MyDll.cpp
#include "MyDll.h"
namespace Functions{
Person MyFunctions::first() {
struct Person myPerson;
myPerson.name = "asd";
myPerson.age = 123;
return myPerson;
}
}

//MyDll.h
namespace Functions{
struct Person {
char *name;
int age;
};
class MyFunctions {
public:
static __declspec(dllexport) Person first();
};
}

Then the DLL file I paste in the new project folder (only this one, because for my point of view I don't need nothing more, because it is very simple and doesn't use/depend nothing more ), right?

In the new project I made:

#include "stdafx.h"
#include "windows.h"
using namespace System;

int main(array<System::String ^> ^args){
HINSTANCE myDll = LoadLibrary((LPCWSTR)"TestingDll.dll");
if(myDll) {
Console::WriteLine("DLL loaded \n");
}
else {
Console::WriteLine("DLL failed to load \n");
}
return 0;
}

And the result always is -> "DLL failed to load".

It doesn't returns any error, but doesn't do what I want .
I apologize, but due to my inexperience I did not understand the problem that could cause this ( for sure is something that I'm doing wrong, or forget).
Can you help me?

CPallini16-Feb-09 6:52

16-Feb-09 6:52

From LoadLibrary documentation [^].

Return Value

If the function succeeds, the return value is a handle to the module.

If the function fails, the return value is NULL. To get extended error information, call GetLastError.

BTW possibly you should put the DLL inside the project folder.
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

Member Ártemis16-Feb-09 7:18

16-Feb-09 7:18

Thanks for your atention...
I already have the DLL inside the new project folder, but it still not work Frown | :(

and I couldn't understand what could be the cause of this, because it doesn't return any error...

CPallini16-Feb-09 7:38

16-Feb-09 7:38

As stated by the documentation I linked in my previous post, if the LoadLibrary return HANDLE is NULL then you have to call GetLastError in order to get some understanding of what's happening.
Smile | :)

regnwald16-Feb-09 18:44

regnwald

16-Feb-09 18:44

Perhaps your quote on Creation could be applied to the other Lord who has created so many dialects of C with so many obscure confusions in syntax.

Regards
Ron

CPallini16-Feb-09 21:34

16-Feb-09 21:34

Maybe. Anyway, strictly speaking, the obstacles that are hurting the OP are functions of an application programming interface (Win32 API): he isn't dealing with a C language dialect.
Smile | :)

CPallini16-Feb-09 21:44

16-Feb-09 21:44

Again, CByteArray members GetData & GetSize (togheter with std::string constructor) do the trick, for instance:

CByteArray arr;
arr.Add(0xff);
arr.Add(0x00);
arr.Add(0x10);
arr.Add(0x41);
std::string str((char*) arr.GetData(), arr.GetSize());

Richard Andrew x6416-Feb-09 16:37

Richard Andrew x64

16-Feb-09 16:37

Are you using Visual Studio 2005 or 2008?

You may notice that the Visual Studio puts your exe in a folder called "debug" at the same level as your project folder.

The "debug" folder that's inside your project folder holds only the obj files, and the exe does not run from there.

You have to make sure that you put the DLL into the same folder where the exe file is created.

Solution Folder<br />
  |<br />
  |---Project Folder<br />
  |       |<br />
  |       |-Debug<br />
  |<br />
  |---Debug <= Put dll here<br />

Member Ártemis16-Feb-09 23:04

16-Feb-09 23:04

I'm using Visual Studio 2008.
I had been careful to paste the DLL in the folder with the .exe file... But it still doesn't work...
It is the first time I tried to do a DLL, it is possible I forgot something, or maybe I'm doing something wrong... Confused | :confused:

Richard Andrew x6417-Feb-09 2:00

Richard Andrew x64

17-Feb-09 2:00

Does your DllMain() function return TRUE?

A Dll will only load if its DllMain() function returns TRUE.

Member Ártemis17-Feb-09 4:56

17-Feb-09 4:56

I think my DLL code is correct, because I used the DLL in a c# project and it loaded and worked just fine.
My problem is to load in a c++ project.
I read that if we want to use a DLL without de lib file, we must paste de DLL file in the debug project folder (and I did it, because I want it to work without the code files).
Then I used
HINSTANCE myDll = LoadLibrary((LPCWSTR)"Testing.dll");
if(myDll)
Console::WriteLine("DLL loaded \n");
else
Console::WriteLine("DLL failed to load \n");

it always "DLL failed to load ", it doesn't return any error.
Did I forgot something, or am I doing something wrong? (I'm starting with c++, so possible I'm making some mistake).

Thanks.

Richard Andrew x6417-Feb-09 12:33

Richard Andrew x64

17-Feb-09 12:33

Change your code so that it reads as follows:

HINSTANCE myDll = LoadLibrary((LPCWSTR)"Testing.dll");

DWORD Error = GetLastError();

if (myDll)
   Console::Writeline("Dll Loaded");
else
   Console::Writeline("Dll Not Loaded");

Put a breakpoint at the line that says "Not Loaded."

When the program breaks, inspect the value of the variable Error.

That will be the Windows error code for what went wrong. Post the Error code here, and maybe we can help you figure it out.

Member Ártemis17-Feb-09 23:46

Convert const string& to CByteArray ?

17-Feb-09 23:46

Hi.
Thanks a lot for your help.
I did what you suggested and I got error 126 (unsigned int).
I made a litle search to understand error 126 and its causes...and I found out that I can't cast char* to LPCWSTR, and the solution is just "Use Multi-Byte Character Set" within the projects properties. And it works just fine.

Best regards,
Carla

mmayur16-Feb-09 5:27

16-Feb-09 5:27

Hi,

How do i convert a const string& to CByteArray ?

I have to convert the string to CByteArray and pass the member functions GetData() and GetSize() to a method as parameters

Is it possible or is there an alternative way of converting string to CByteArray.

An example would be appreciated.

Thanks in advance,

Regards,
Mayur M

CPallini16-Feb-09 8:05

16-Feb-09 8:05

Try (I didn't test it...)

CString str = _T("Hi");
CByteArray arr;
int iSize = (str.GetLength()+1) * sizeof(TCHAR) 
const BYTE * pByte = (const BYTE *) (LPCTSTR) str;
for (i = 0; i < iSize; i++)
{
  arr.Add(pByte[i]);
}

mmayur16-Feb-09 8:46

16-Feb-09 8:46

Thanks for your reply.

The code snippet works fine. But the snippet is for convertion of CString to CByteArray. But i'm looking for a const string conversion to CByteArray.

Even if i use the CString conversion to CByteArray, is there any inbuilt methods rather than using the for loop.

Regards,
Mayur M

CPallini16-Feb-09 9:46

16-Feb-09 9:46

mayur8u wrote:
But i'm looking for a const string conversion to CByteArray.

Are you talking about std::string?

mayur8u wrote:
Even if i use the CString conversion to CByteArray, is there any inbuilt methods rather than using the for loop.

Yes, you may use CByteArray methods SetSize and Getdata to copy the string content into the array buffer.

CString str = _T("Hi");
CByteArray arr;
int iSize = (str.GetLength()+1) * sizeof(TCHAR) 
arr.SetSize(iSize);
const BYTE * pByte = (const BYTE *) (LPCTSTR) str;
CopyMemory( arr.GetData(), pByte, iSize);

As usual, the test is up to you.

Smile | :)

mmayur16-Feb-09 10:02

16-Feb-09 10:02

Ya! i'm talking about converting from std::string to CByteArray.

If there is no solution then i might have to go to CString. (Last option)

CPallini16-Feb-09 10:51

16-Feb-09 10:51

std::string str("Hi");
int iLen = str.length();
CByteArray arr;
arr.SetSize(iLen);
CopyMemory( arr.GetData(), str.c_str(), iLen);

Please note, the above code is not adding the null terminator at the tail of the array.
Smile | :)

mmayur16-Feb-09 11:27

16-Feb-09 11:27

How about the CByteArray to std:string?

mmayur17-Feb-09 9:15