Dll is not loading properly using loadlibrary in VS 2019

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Below is the code of DLL (Compiled in VS2019 v142, SDK 10,Debug mode) compiled successfully. Loading this DLL using LoadLibrary()in MFC program(Compiled in VS2019 v142 , Sdk 10,Debug Mode). Both code works fine in VS2010. But not woking in VS2017.

C++

#include "stdafx.h"
#include "SiTempJCL.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

BEGIN_MESSAGE_MAP(SiJCLTemplateDfltApp, CWinApp)
	
END_MESSAGE_MAP()


SiJCLTemplateDfltApp::SiJCLTemplateDfltApp()
{
	// TODO: add construction code here,
	// Place all significant initialization in InitInstance
}


SiJCLTemplateDfltApp theApp;

extern "C" __declspec( dllexport )

CSResult* FireRule(CObList& list)
{
	AFX_MAINTAIN_STATE2 *pState = new AFX_MAINTAIN_STATE2(AfxGetStaticModuleState());
	try 
	{
		
		CString *sJobTemplate;
		CString sDBUseCode="M";
		if((sDBUseCode == "M") || (sDBUseCode == "P")) {
			sJobTemplate = new CString("JOBM");
		}
		else {
			sJobTemplate = new CString("JOBC");
		}

		// Return JCL job template id
		CSResult *ruleRet = new CSResult();
		ruleRet->SetReturnObject((CObject *) sJobTemplate);

		delete pState;
		return ruleRet;
	}
	catch (...)
	{
		delete pState;
		throw;
	}
}

What I have tried:

Code for Calling above DLL:

C++

HINSTANCE         hModule;
hModule = LoadLibrary("SiJCLTemplate.dll");

SiLauncherApp* pSiBatchLauncherApp1 = (SiLauncherApp*)AfxGetApp();

I have checked hModule is not null, loading the dll and calling firerule function.
but i think it is not loading properly. as when i check

pSiBatchLauncherApp1
object after loadlibrary, it shows me

{SiJCLTemplateDfltApp.dll!SiJCLTemplateDfltApp theApp<NULL>};
.

I am assuming there is some problem in DLL code . may be little change is required which is not supportive in MS2017.

Please guide.

Posted 13-Jul-20 4:44am

Member 13261094

Updated 13-Jul-20 20:00pm

v3

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2 solutions

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This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Richard MacCutchan · Answer 1 · 2020-07-13T05:31:00

Solution 1

The only thing I see is that your dll is missing its DllMain function, as described at DllMain entry point (Process.h) - Win32 apps | Microsoft Docs[^].

Posted 13-Jul-20 5:31am

Richard MacCutchan

Comments

Shao Voon Wong 14-Jul-20 3:44am

Indeed!

Richard MacCutchan 14-Jul-20 4:12am

Although from further comments it appears that this is not necessary. Maybe it is added automatically by MFC.

Shao Voon Wong · Answer 2 · 2020-07-13T18:09:00

Solution 2

CString is not derived from CObject so you cannot cast its pointer to CObject*.

C++

CString* p_str = new CString(L"Hello");
CObject* p_obj = p_str;

I got this error from VC++ 2019:

error C2440: 'initializing': cannot convert from 'CString *' to 'CObject *'

Highly probable, CString used to inherit from CObject in older VC++ but not now.

Posted 13-Jul-20 18:09pm

Shao Voon Wong

Updated 13-Jul-20 19:27pm

v2

Comments

Member 13261094 14-Jul-20 2:02am

Not getting any compilation error. It loading library and executing the dll function also. Only thing It corrupts the pSiBatchLauncherApp1 object.

Shao Voon Wong 14-Jul-20 3:19am

It is because your C-style cast silence the compiler. No compilation error for the code below. This is why C-style cast is discouraged.

CString* p_str = new CString(L"Hello");
CObject* p_obj = (CObject*)p_str;

But this original code will have a compilation error.

CString* p_str = new CString(L"Hello");
CObject* p_obj = p_str;

Shao Voon Wong 14-Jul-20 3:56am

Remember to make the function and the function pointer the same calling convention, as mentioned in your previous question thread.

https://en.wikipedia.org/wiki/X86_calling_conventions

The function declaration should be

siRuleReturn* WINAPI FireRule(CObList& list);

And the function pointer declaration should be

siRuleReturn* (WINAPI* FIRERULE)(CObList& list);

Shao Voon Wong 14-Jul-20 4:07am

You can do the cause elimination by commenting out the lines starting from the bottom until the crash does not happen. Then you know the recent commented-out line is the cause.

Dll is not loading properly using loadlibrary in VS 2019

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