Re: variable solution compiles, but I can't get at value: - C / C++ / MFC Discussion Boards

hxhl958-Nov-07 11:37

8-Nov-07 11:37

I wasn't sure where to post this, but since the code I'm having problems on is in my MFC app, I'm posting it here.

I have an RDTSC function in my code. It uses the RDTSC instruction to obtain a value in EDX:EAX. I need to print that value out before the function exits. How do I do that?

(I realize that this might be a stupid question, since I've only been working in assembly for around 3 months and I'm still learning.)

Thanks in advance. Big Grin | :-D

Re: RDTSC

Mark Salsbery8-Nov-07 12:37

Mark Salsbery

8-Nov-07 12:37

Something like this maybe?

    unsigned __int64 rdtscval;

    __asm
    {
        rdtsc
        lea ebx, rdtscval
        mov [ebx], eax
        mov [ebx+4], edx
    }

    CString str;
    str.Format(_T("%I64u"), rdtscval);

    ::MessageBox(*this, str, _T("rdtsc"), MB_OK);

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

variable solution compiles, but I can't get at value: [modified]

e40s8-Nov-07 11:01

e40s

8-Nov-07 11:01

I've written into some Code Project sample code a solution generously offered to me by a fellow poster for an adaptation to the code I had wanted to make. I had asked the board if there was a way to get at the value inside a variable called strContent here inside of OnDataReady (and one aspect of the solution involved renaming it to m_strContent, the way it's now shown here in this CMemMapCppClientDlg.cpp snip):

LRESULT CMemMapCppClientDlg::OnDataReady(WPARAM, LPARAM) <br />
{<br />
	HANDLE hMapFile = NULL;<br />
	PVOID pView = NULL;<br />
<br />
	hMapFile = OpenFileMapping(FILE_MAP_READ, FALSE, m_pszMemMapFileName);<br />
	if(hMapFile == NULL) {<br />
		MessageBox("Can not open file mapping");<br />
		return 0;<br />
	}<br />
<br />
	pView = MapViewOfFile(hMapFile, FILE_MAP_READ, 0, 0, 0);<br />
	if(pView == NULL) {<br />
		MessageBox("Can map view of file");<br />
		CloseHandle(hMapFile);<br />
		return 0;<br />
	}<br />
<br />
	LPSTR szContent = reinterpret_cast<LPSTR>(pView);<br />
	int nLen = strlen(szContent);<br />
	while(nLen > 0) {<br />
		m_strContent += *szContent++;<br />
		--nLen;<br />
	}<br />
	m_strContent += '\0';<br />
	m_strContent.Replace("\n", "\r\n");<br />
<br />
	if(pView) UnmapViewOfFile(pView);<br />
	if(hMapFile) CloseHandle(hMapFile);<br />
<br />
	return 0;<br />
}<br />
<br />
CString CMemMapCppClientDlg::GetContent()<br />
{<br />
  return m_strContent;<br />
}

Another part of the solution involved adding the ::GetContent() function, shown there immediately above.

Then the appropriate changes were shown to me for the header, here:

// MemMapCppClientDlg.h : header file<br />
//<br />
<br />
#if !defined(AFX_MEMMAPCPPCLIENTDLG_H__A51F6AF7_F28D_461D_8FB3_EFC7B929D99C__INCLUDED_)<br />
#define AFX_MEMMAPCPPCLIENTDLG_H__A51F6AF7_F28D_461D_8FB3_EFC7B929D99C__INCLUDED_<br />
<br />
#if _MSC_VER > 1000<br />
#pragma once<br />
#endif // _MSC_VER > 1000<br />
<br />
/////////////////////////////////////////////////////////////////////////////<br />
// CMemMapCppClientDlg dialog<br />
<br />
class CMemMapCppClientDlg : public CDialog<br />
{<br />
// Construction<br />
public:<br />
	static UINT UWM_DATA_READY;<br />
	CMemMapCppClientDlg(CWnd* pParent = NULL);	// standard constructor<br />
    CString GetContent();<br />
<br />
// Dialog Data<br />
	enum { IDD = IDD_MEMMAPCPPCLIENT_DIALOG };<br />
	// ClassWizard generated virtual function overrides<br />
	protected:<br />
<br />
// Implementation<br />
protected:<br />
	// Generated message map functions<br />
	//{{AFX_MSG(CMemMapCppClientDlg)<br />
	virtual BOOL OnInitDialog();<br />
//[leave the dialog]	afx_msg void CMemMapCppClientDlg::OnWindowPosChanging(WINDOWPOS FAR* lpwndpos);<br />
	afx_msg LRESULT OnDataReady(WPARAM wParam, LPARAM lParam);<br />
	DECLARE_MESSAGE_MAP()<br />
    CString m_strContent; <br />
<br />
private:<br />
	//enum { m_dwMemFileSize = 2 * 1024 };<br />
	LPCTSTR m_pszMemMapFileName;<br />
};<br />
<br />
	#define UWM_DATA_READY_MSG _T("UWM_DATA_READY_MSG-{7FDB2CB4-5510-4d30-99A9-CD7752E0D680}")<br />
<br />
//{{AFX_INSERT_LOCATION}}<br />
// Microsoft Visual C++ will insert additional declarations immediately before the previous line.<br />
<br />
#endif // !defined(AFX_MEMMAPCPPCLIENTDLG_H__A51F6AF7_F28D_461D_8FB3_EFC7B929D99C__INCLUDED_)

And, lastly, here is the MemMapCppClient.cpp that contains the call to GetContent():

// MemMapCppClient.cpp : Defines the class behaviors for the application.<br />
//<br />
...<br />
<br />
VARIANT _stdcall SumOneToArray(VARIANT sourceArray)<br />
{<br />
CMemMapCppClientDlg dlg;<br />
CString strContent = dlg.GetContent();<br />
MessageBox(NULL, _T(strContent), _T("Like this:"), MB_OK);<br />
//MessageBox(NULL, _T("Hey."), _T("Like this:"), MB_OK);<br />
<br />
//check if Array is a Range object<br />
if(sourceArray.vt==VT_DISPATCH)<br />
sourceArray = CheckExcelArray(sourceArray);<br />
<br />
long ncols, nrows, i, j;<br />
<br />
//get the number columns and rows<br />
ncols=(sourceArray.parray)->rgsabound[0].cElements;<br />
nrows=(sourceArray.parray)->rgsabound[1].cElements;<br />
<br />
...<br />
}<br />
...

I've gone and stuck the...

CMemMapCppClientDlg dlg;<br />
CString strContent = dlg.GetContent();<br />
MessageBox(NULL, _T(strContent), _T("Like this:"), MB_OK);

...inside the top of one of the functions. The project won't compile if I put those statements anywhere else in the function, like in the middle. I get "initialization" errors.

The question is this: Even when all of this compiles perfectly, and my program works great--even the MessageBox gets displayed on cue--no content is there in the MessageBox. Never in any incarnation of a successful compile do I get content within the MessageBox. The prog always works perfectly otherwise.

(I know for a fact content is otherwise available in m_strContent over in the MemMapCppClient.cpp because if I put the MessageBox over there, I get m_strContent just fine.)

I botched this somehow. How can I get a value into the MessageBox inside of CMemMapCppClientApp?

Thanks again for all your help.

-- modified at 18:45 Thursday 8th November, 2007

Re: variable solution compiles, but I can't get at value:

Llasus8-Nov-07 12:53

Llasus

8-Nov-07 12:53

e40s wrote:
So, one question is how do I use CMemMapCppClientDlg dlg;
elsewhere in the MemMapCppClient.cpp while still retaining the apps compilability?

Do the same thing that you have done earlier with the CString m_strContent by declaring the CMemMapCppClientDlg on the MemMapCppClient.h. Try if that works first.

e40s wrote:
The bigger question is this: Even when all of this compiles perfectly, and my program works great--even the MessageBox gets displayed on cue--no content is there in the MessageBox. Never in any incarnation of a successful compile do I get content within the MessageBox. The prog always works perfectly otherwise.

Make it into this: MessageBox(strContent, _T("Like this:"));
By default the message box has an OK button so no need to add MB_OK there.

Re: variable solution compiles, but I can't get at value:

e40s9-Nov-07 4:30

e40s

9-Nov-07 4:30

That suggestion works in some other parts of the program, but in this, MessageBoxA demands four arguments.

But there is something else I'm noticing: The strContent may never appear in the box because it's never arriving from GetContent().

In MemMapCppClientDlg, I added a MessageBox() to GetContent(), above the return, like so:

MessageBox(_T(m_strContent), _T("Forget this."));<br />
return m_strContent;

and got no content inside the MessageBox's client area. It's possible m_strContent isn't delivering a value.

Can someone please look at this--maybe specifically the header file, and see if something's lacking. A pointer maybe? I don't know; I'm lost.

Thanks again all.

Offtopic

Nelek8-Nov-07 21:39

Nelek

8-Nov-07 21:39

It will be better if you use the < pre > < /pre > tags to englobe pieces of code, and the < code > < /code > to highlight little things. Is easier to read on the other way. And with pre the horizontal limit for a line is bigger, so commands won't be broken in different lines not so oft.

EDIT: Maybe a Site Admin could change the label from tags.
code -> Highlight (or something like that)
pre -> snippet (or something like that)

I had the same mistake at the beggining, I thought "paste code = code tag"

Greetings.

--------
M.D.V.

If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about?

Help me to understand what I'm saying, and I'll explain it better to you

Wink | ;)

Re: Offtopic

e40s9-Nov-07 5:14

e40s

9-Nov-07 5:14

Thanks for this, Nelek. I didn't know about pre.

Re: variable solution compiles, but I can't get at value:

David Crow9-Nov-07 4:39

David Crow

9-Nov-07 4:39

Limit your use of the _T() macro to string literals, not variables.

e40s wrote:
I get "initialization" errors.

This is too vague. What statement produces this?

e40s wrote:
CString strContent = dlg.GetContent();

At this point has CMemMapCppClientDlg::OnDataReady() been called to add content to m_strContent? If not, MessageBox() will obviously show nothing.

Why not use AfxMessageBox() instead? It won't solve your problem, but it takes much less code.

"Normal is getting dressed in clothes that you buy for work and driving through traffic in a car that you are still paying for, in order to get to the job you need to pay for the clothes and the car and the house you leave vacant all day so you can afford to live in it." - Ellen Goodman

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Re: variable solution compiles, but I can't get at value: [modified]

e40s9-Nov-07 5:02

e40s

9-Nov-07 5:02

Thanks for replying David.

>> Limit your use of the _T() macro to string literals, not variables.
Thanks for the education. Will do.

>> This is too vague. What statement produces this?
My fault for bringing that initialization stuff up. I was straddling the statement in select case areas where I shouldn't have been. That problem's been solved, I believe, and pales in comparison to this:

>> At this point has CMemMapCppClientDlg::OnDataReady() been called to add content to m_strContent? If not, MessageBox() will obviously show nothing.
Yes. And that's the mystery.

But now I've confirmed, as I've written this morning, that even a MessageBox() statement inside of GetContent() fails to reveal the value of m_strContent. What's up with that?

(See, the thing is, if I take the comments off of the message box inside ::OnDataReady, the value appears just fine over there.)

Something missing from the header file? From the source? I wrote it up wrong from BK's script? I dunno.

>> Why not use AfxMessageBox() instead? It won't solve your problem, but it takes much less code.
Okay. I didn't know about that one.

-- modified at 11:18 Friday 9th November, 2007

Re: variable solution compiles, but I can't get at value:

David Crow9-Nov-07 5:34

David Crow

9-Nov-07 5:34

e40s wrote:
Yes. And that's the mystery.

But according to the code snippet you've shown, OnDataReady() has not been called prior to calling GetContent(). You are constructing a CMemMapCppClientDlg object and immediately calling GetContent() which will obviously return an empty string.

Re: variable solution compiles, but I can't get at value: [modified]

e40s9-Nov-07 6:03

e40s

9-Nov-07 6:03

This is my observation.

My Excel file loads this DLL (the whole thing you're looking at in code). It's a DLL because I transmogrified the CodeProject sample from an .exe into one. Because it was originally authored as a Dlg, that window aspect of it remains. Anyway, when the Excel file loads this DLL, said Dialog immediately gets displayed on the screen (it's small and mostly blank, with a simple label in the center). Its job is to pass messages--because only a window can do that, evidently. When I'm finished with it, I destroy the window with a PostMessage().

Anyway, nothing happens display-wise--besides that dialog sitting there--until I fire up the Java side of this, which dispatches a message, via JNI, that is received by this DLL precisely at ::OnDataReady. Whatever content that JNI has passed immediately lands in m_strContent, and lights up the uncommented MessageBox.

To my knowledge, the Excel file way over at the other side does not touch OnDataReady. (Or I hope not. I don't want it to.) Excel is playing only at the CMemMapCppClientApp side--not the CMemMapCppClientDlg side.

Excel, and its loading of the DLL, never touch OnDataReady. (If they did, I would have seen the uncommented MessageBox inside OnDataReady light up immediately upon such an event. I never do.)

It is later, using Excel after Excel has already loaded the DLL prior, I only attempt to retrieve m_strContent value after JNI has already infilled it on the OnDataReady side. [The motivation for yesterday's and today's threads.] If I hear you right, you're suggesting that my invocation of the DLL at any time from Excel has an impact on OnDataReady. Because I never see any evidence of that--i.e., the uncommented MessageBox inside OnDataReady--I don't believe that suggested sequence of events to be the case.

I am calling CMemMapCppClientDlg::GetContent() exclusively from Excel by way of CMemMapCppClientApp. That action per se never, and shouldn't if I'm not mistaken (correct me if I'm wrong), in any way have an impact on OnDataReady. It can't.

-- modified at 12:25 Friday 9th November, 2007

Re: variable solution compiles, but I can't get at value:

David Crow9-Nov-07 6:20

David Crow

9-Nov-07 6:20

All this extra stuff aside, the fact still remains that:

CMemMapCppClientDlg dlg;
CString strContent = dlg.GetContent();
MessageBox(NULL, strContent, _T("Like this:"), MB_OK);

will do nothing but display an empty message box. You can verify this by initializing m_strContent to something in CMemMapCppClientDlg's constructor.

After looking at what you've provided, it seems you have two instances of CMemMapCppClientDlg: the main one instantiated from CMemMapCppClientApp::InitInstance(), and another one instantiated from SumOneToArray(). Is that correct?

Re: variable solution compiles, but I can't get at value: [modified]

e40s9-Nov-07 6:36

e40s

9-Nov-07 6:36

>>After looking at what you've provided, it seems you have two instances of CMemMapCppClientDlg: the main one instantiated from CMemMapCppClientApp::InitInstance(), and another one instantiated from SumOneToArray(). Is that correct?
I don't believe so, but I can't say for certain. Can you tell me? Here's the full MemMapCppClient.cpp (ole2.h doesn't show up in our display here for the second #include because it's enclosed in less than/greater than punctuations):

// MemMapCppClient.cpp : Defines the class behaviors for the application.
//

#include "stdafx.h"
#include <ole2.h>
#include "MemMapCppClient.h"
#include "MemMapCppClientDlg.h"

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

VARIANT _stdcall CheckExcelArray(VARIANT& ExcelArray)
{
VARIANT dvout;
switch(ExcelArray.vt)
{
case VT_DISPATCH:
// if Array is a Range object expose its values through the 
//IDispatch interface
{
EXCEPINFO excep;
DISPPARAMS dispparams;
unsigned int uiArgErr;
DISPID dispidValue;
LPOLESTR XName = L"Value";

ExcelArray.pdispVal->GetIDsOfNames(IID_NULL, &XName,
        1, LOCALE_SYSTEM_DEFAULT, &dispidValue);

dispparams.cArgs = 0;
dispparams.cNamedArgs = 0;

// Invoke PropertyGet and store values in dvout
ExcelArray.pdispVal->Invoke(dispidValue, IID_NULL,
LOCALE_SYSTEM_DEFAULT, DISPATCH_PROPERTYGET, 
&dispparams, &dvout, &excep, &uiArgErr);

ExcelArray.pdispVal->Release();

return dvout;
}

break;

default:
//if the Array is a VBA SAFEARRAY return it as such
return ExcelArray;
break;
}
VariantClear(&dvout);
VariantClear(&ExcelArray);
}

VARIANT _stdcall SumOneToArray(VARIANT sourceArray)
{
CMemMapCppClientDlg dlg;
CString strContent = dlg.GetContent();
//MessageBox(NULL, strContent, _T("Like this:"), MB_OK);
//MessageBox(NULL, _T("Hey."), _T("Like this:"), MB_OK);

//check if Array is a Range object
if(sourceArray.vt==VT_DISPATCH)
sourceArray = CheckExcelArray(sourceArray);

long ncols, nrows, i, j;

//get the number columns and rows
ncols=(sourceArray.parray)->rgsabound[0].cElements;
nrows=(sourceArray.parray)->rgsabound[1].cElements;

//dynamically allocate memory for an array to store values
VARIANT *dArray = new VARIANT [nrows*ncols];

for(i=0; i<nrows; i++)
{
for(j=0; j<ncols; j++)
{
long indi[] = {i+1,j+1};
//store in a VARIANT array for other uses 
SafeArrayGetElement(sourceArray.parray, indi, &dArray[(i*ncols)+j]);

}
}

//create a VARIANT SAFEARRAY to return modified values
VARIANT destArray;
destArray.vt = VT_ARRAY | VT_VARIANT;

SAFEARRAYBOUND sab[2];
sab[0].lLbound = 1; sab[0].cElements = nrows;
sab[1].lLbound = 1; sab[1].cElements = ncols;
destArray.parray = SafeArrayCreate(VT_VARIANT, 2, sab);

for(i=0; i<nrows; i++)
{
for(j=0; j<ncols; j++)
{
long indi[] = {i+1,j+1};

//check for the type of VARIANT in the array
switch(dArray[(i*ncols)+j].vt)
{
case VT_I2:
dArray[(i*ncols)+j].iVal=dArray[(i*ncols)+j].iVal + 1;
// dArray[(i*ncols)+j].iVal=1000;
break;

case VT_R8:
dArray[(i*ncols)+j].dblVal=dArray[(i*ncols)+j].dblVal + 1;
// dArray[(i*ncols)+j].dblVal=3700;
break;

//Hope the interested reader can perform more interesting operations!
//So here You need to add checking for the rest of VARIANT types
//there are plenty of them and You need to know what types your
//array may hold!

default:
break;
}

//Put the result in the array to be returned to Excel or the VBA env.
SafeArrayPutElement(destArray.parray, indi, &dArray[(i*ncols)+j]);
}
}

//free memory of the intermediate storage variable
delete [] dArray;

//return the modified array to SpreadSheet or VBA environment
return destArray;

//free memory for VARIANTs
VariantClear(&sourceArray);
VariantClear(&destArray);
}

/////////////////////////////////////////////////////////////////////////////
// CMemMapCppClientApp

BEGIN_MESSAGE_MAP(CMemMapCppClientApp, CWinApp)
END_MESSAGE_MAP()

//[leave the dialog]:
//void CMemMapCppClientDlg::OnWindowPosChanging(WINDOWPOS FAR* lpwndpos) 
//{
//    lpwndpos->flags &= ~SWP_SHOWWINDOW;
//    CDialog::OnWindowPosChanging(lpwndpos);
//}

/////////////////////////////////////////////////////////////////////////////
// CMemMapCppClientApp construction

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

/////////////////////////////////////////////////////////////////////////////
// The one and only CMemMapCppClientApp object

CMemMapCppClientApp theApp;

/////////////////////////////////////////////////////////////////////////////
// CMemMapCppClientApp initialization

BOOL CMemMapCppClientApp::InitInstance()
{
	CMemMapCppClientDlg dlg;
	m_pMainWnd = &dlg;
	int nResponse = dlg.DoModal();

//	MessageBox(NULL, _T(LPSTR (m_pMainWnd)), "Whatever", MB_OK);

	return FALSE;
}

Here's the full MemMapCppClientDlg.cpp:

// MemMapCppClientDlg.cpp : implementation file
//

#include "stdafx.h"
#include "MemMapCppClient.h"
#include "MemMapCppClientDlg.h"

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

UINT CMemMapCppClientDlg::UWM_DATA_READY = RegisterWindowMessage(UWM_DATA_READY_MSG); 
/////////////////////////////////////////////////////////////////////////////
// CMemMapCppClientDlg dialog

CMemMapCppClientDlg::CMemMapCppClientDlg(CWnd* pParent /*=NULL*/)
	: CDialog(CMemMapCppClientDlg::IDD, pParent)
{
	m_pszMemMapFileName = _T("Mem_Map_File-{70122C30-0239-4f98-9D21-36885C8A8121}");
}

BEGIN_MESSAGE_MAP(CMemMapCppClientDlg, CDialog)
//[leave the dialog]	ON_WM_WINDOWPOSCHANGING()
	ON_REGISTERED_MESSAGE(UWM_DATA_READY, OnDataReady)
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CMemMapCppClientDlg message handlers

BOOL CMemMapCppClientDlg::OnInitDialog()
{
	CDialog::OnInitDialog();

	return TRUE;  // return TRUE  unless you set the focus to a control
}

LRESULT CMemMapCppClientDlg::OnDataReady(WPARAM, LPARAM) 
{
	HANDLE hMapFile = NULL;
	PVOID pView = NULL;

	hMapFile = OpenFileMapping(FILE_MAP_READ, FALSE, m_pszMemMapFileName);
	if(hMapFile == NULL) {
		MessageBox("Can not open file mapping");
		return 0;
	}

	pView = MapViewOfFile(hMapFile, FILE_MAP_READ, 0, 0, 0);
	if(pView == NULL) {
		MessageBox("Can map view of file");
		CloseHandle(hMapFile);
		return 0;
	}

	LPSTR szContent = reinterpret_cast<LPSTR>(pView);
	int nLen = strlen(szContent);
	CString m_strContent;
	while(nLen > 0) {
		m_strContent += *szContent++;
		--nLen;
	}
	m_strContent += '\0';
	m_strContent.Replace("\n", "\r\n");
////	m_edit.SetWindowText(m_strContent);
    MessageBox(m_strContent);

	if(pView) UnmapViewOfFile(pView);
	if(hMapFile) CloseHandle(hMapFile);

	return 0;
}

CString CMemMapCppClientDlg::GetContent()
{
    MessageBox(m_strContent, _T("Forget this."));
	return m_strContent;
}

The full MemMapCppClient.h

// MemMapCppClient.h : main header file for the MEMMAPCPPCLIENT application
//

#if !defined(AFX_MEMMAPCPPCLIENT_H__6FC73066_4FE5_46F4_891C_2434753F81AA__INCLUDED_)
#define AFX_MEMMAPCPPCLIENT_H__6FC73066_4FE5_46F4_891C_2434753F81AA__INCLUDED_

#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000

#ifndef __AFXWIN_H__
	#error include 'stdafx.h' before including this file for PCH
#endif

#include "resource.h"		// main symbols

// CMemMapCppClientApp
// See MemMapCppClient.cpp for the implementation of this class
//

class CMemMapCppClientApp : public CWinApp
{
public:
	CMemMapCppClientApp();

// Overrides
public:
	virtual BOOL InitInstance();

	DECLARE_MESSAGE_MAP()
};

#endif // !defined(AFX_MEMMAPCPPCLIENT_H__6FC73066_4FE5_46F4_891C_2434753F81AA__INCLUDED_)

The full MemMapCppClientDlg.h:

// MemMapCppClientDlg.h : header file
//

#if !defined(AFX_MEMMAPCPPCLIENTDLG_H__A51F6AF7_F28D_461D_8FB3_EFC7B929D99C__INCLUDED_)
#define AFX_MEMMAPCPPCLIENTDLG_H__A51F6AF7_F28D_461D_8FB3_EFC7B929D99C__INCLUDED_

#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000

/////////////////////////////////////////////////////////////////////////////
// CMemMapCppClientDlg dialog

class CMemMapCppClientDlg : public CDialog
{
// Construction
public:
	static UINT UWM_DATA_READY;
	CMemMapCppClientDlg(CWnd* pParent = NULL);	// standard constructor
        CString GetContent();

// Dialog Data
	enum { IDD = IDD_MEMMAPCPPCLIENT_DIALOG };
	// ClassWizard generated virtual function overrides
	protected:

// Implementation
protected:
	// Generated message map functions
	//{{AFX_MSG(CMemMapCppClientDlg)
	virtual BOOL OnInitDialog();
//[leave the dialog]	afx_msg void CMemMapCppClientDlg::OnWindowPosChanging(WINDOWPOS FAR* lpwndpos);
	afx_msg LRESULT OnDataReady(WPARAM wParam, LPARAM lParam);
	DECLARE_MESSAGE_MAP()
	CString m_strContent; 

private:
	//enum { m_dwMemFileSize = 2 * 1024 };
	LPCTSTR m_pszMemMapFileName;
};

	#define UWM_DATA_READY_MSG _T("UWM_DATA_READY_MSG-{7FDB2CB4-5510-4d30-99A9-CD7752E0D680}")

//{{AFX_INSERT_LOCATION}}
// Microsoft Visual C++ will insert additional declarations immediately before the previous line.

#endif // !defined(AFX_MEMMAPCPPCLIENTDLG_H__A51F6AF7_F28D_461D_8FB3_EFC7B929D99C__INCLUDED_)

-- modified at 12:41 Friday 9th November, 2007

Re: variable solution compiles, but I can't get at value:

David Crow9-Nov-07 6:40

David Crow

9-Nov-07 6:40

e40s wrote:
I don't believe so...

I do. Observe:

VARIANT _stdcall SumOneToArray(VARIANT sourceArray)
{
    CMemMapCppClientDlg dlg;
    CString strContent = dlg.GetContent();
    ...
}
 
BOOL CMemMapCppClientApp::InitInstance()
{	
    CMemMapCppClientDlg dlg;	
    m_pMainWnd = &dlg;
    dlg.DoModal();
    ...
}

Re: variable solution compiles, but I can't get at value:

e40s9-Nov-07 6:45

e40s

9-Nov-07 6:45

Whoa! How'd you do that? Smile | :)

I'll pull it and see what happens.

Re: variable solution compiles, but I can't get at value:

e40s9-Nov-07 6:47

e40s

9-Nov-07 6:47

So how do I get around this?

Re: variable solution compiles, but I can't get at value:

David Crow9-Nov-07 6:52

David Crow

9-Nov-07 6:52

One way is to make the member variable static. This means that GetContent() will also need to be static.

Your next question (regarding scope) can be answered here.

Re: variable solution compiles, but I can't get at value: [modified]

e40s9-Nov-07 7:04

e40s

9-Nov-07 7:04

Okay, I changed it to this:

// MemMapCppClientDlg.h : header file
//

#if !defined(AFX_MEMMAPCPPCLIENTDLG_H__A51F6AF7_F28D_461D_8FB3_EFC7B929D99C__INCLUDED_)
#define AFX_MEMMAPCPPCLIENTDLG_H__A51F6AF7_F28D_461D_8FB3_EFC7B929D99C__INCLUDED_

#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000

/////////////////////////////////////////////////////////////////////////////
// CMemMapCppClientDlg dialog

class CMemMapCppClientDlg : public CDialog
{
// Construction
public:
	static UINT UWM_DATA_READY;
	CMemMapCppClientDlg(CWnd* pParent = NULL);	// standard constructor
         static CString GetContent();

// Dialog Data
	enum { IDD = IDD_MEMMAPCPPCLIENT_DIALOG };
	// ClassWizard generated virtual function overrides
	protected:

// Implementation
protected:
	// Generated message map functions
	//{{AFX_MSG(CMemMapCppClientDlg)
	virtual BOOL OnInitDialog();
//[leave the dialog]	afx_msg void CMemMapCppClientDlg::OnWindowPosChanging(WINDOWPOS FAR* lpwndpos);
	afx_msg LRESULT OnDataReady(WPARAM wParam, LPARAM lParam);
	DECLARE_MESSAGE_MAP()
	static CString m_strContent; 

private:
	//enum { m_dwMemFileSize = 2 * 1024 };
	LPCTSTR m_pszMemMapFileName;
};

	#define UWM_DATA_READY_MSG _T("UWM_DATA_READY_MSG-{7FDB2CB4-5510-4d30-99A9-CD7752E0D680}")

//{{AFX_INSERT_LOCATION}}
// Microsoft Visual C++ will insert additional declarations immediately before the previous line.

#endif // !defined(AFX_MEMMAPCPPCLIENTDLG_H__A51F6AF7_F28D_461D_8FB3_EFC7B929D99C__INCLUDED_)

Fascinating. (I mean that sincerely.) Well, the first thing it did was change the argument disposition of MessageBox inside of GetContent(), so I commented that MessageBox line out there.

Attempted a recompile.

The errors:

1>MemMapCppClientDlg.obj : error LNK2001: unresolved external symbol "protected: static class ATL::CStringT<char,class StrTraitMFC_DLL<char,class ATL::ChTraitsCRT<char> > > CMemMapCppClientDlg::m_strContent" (?m_strContent@CMemMapCppClientDlg@@1V?$CStringT@DV?$StrTraitMFC_DLL@DV?$ChTraitsCRT@D@ATL@@@@@ATL@@A)
1>c:\experimental sample\Debug\MFC_DLL_03.dll : fatal error LNK1120: 1 unresolved externals
1>Build log was saved at "file://c:\experimental sample\MFC_DLL_03\Debug\BuildLog.htm"

-- modified at 13:12 Friday 9th November, 2007

Re: variable solution compiles, but I can't get at value:

David Crow9-Nov-07 7:11

David Crow

9-Nov-07 7:11

You have not initialized m_strContent. Static data members of classes must be initialized at file scope.

Re: variable solution compiles, but I can't get at value:

e40s9-Nov-07 7:23

e40s

9-Nov-07 7:23

The link was informative. (For the future, especially about their inability to access non-static class member data using the member-selection operators mentioned. Learning more every day.)

What I tried:

// MemMapCppClientDlg.h : header file
//

#if !defined(AFX_MEMMAPCPPCLIENTDLG_H__A51F6AF7_F28D_461D_8FB3_EFC7B929D99C__INCLUDED_)
#define AFX_MEMMAPCPPCLIENTDLG_H__A51F6AF7_F28D_461D_8FB3_EFC7B929D99C__INCLUDED_

#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000

/////////////////////////////////////////////////////////////////////////////
// CMemMapCppClientDlg dialog

class CMemMapCppClientDlg : public CDialog
{
// Construction
public:
	static UINT UWM_DATA_READY;
	CMemMapCppClientDlg(CWnd* pParent = NULL);	// standard constructor
         static CString CMemMapCppClientDlg::GetContent();

// Dialog Data
	enum { IDD = IDD_MEMMAPCPPCLIENT_DIALOG };
	// ClassWizard generated virtual function overrides
	protected:

// Implementation
protected:
	// Generated message map functions
	//{{AFX_MSG(CMemMapCppClientDlg)
	virtual BOOL OnInitDialog();
//[leave the dialog]	afx_msg void CMemMapCppClientDlg::OnWindowPosChanging(WINDOWPOS FAR* lpwndpos);
	afx_msg LRESULT OnDataReady(WPARAM wParam, LPARAM lParam);
	DECLARE_MESSAGE_MAP()
	static CString CMemMapCppClientDlg::m_strContent; 

private:
	//enum { m_dwMemFileSize = 2 * 1024 };
	LPCTSTR m_pszMemMapFileName;
};

	#define UWM_DATA_READY_MSG _T("UWM_DATA_READY_MSG-{7FDB2CB4-5510-4d30-99A9-CD7752E0D680}")

//{{AFX_INSERT_LOCATION}}
// Microsoft Visual C++ will insert additional declarations immediately before the previous line.

#endif // !defined(AFX_MEMMAPCPPCLIENTDLG_H__A51F6AF7_F28D_461D_8FB3_EFC7B929D99C__INCLUDED_)

Darn. Same errors. (Afterward I even tried adding scope resolution to some of the statements on the .cpp. Nothing changed for the better so I took those off.)

Re: variable solution compiles, but I can't get at value:

David Crow9-Nov-07 7:28

David Crow

9-Nov-07 7:28

e40s wrote:
static CString CMemMapCppClientDlg::m_strContent;

Remove CMemMapCppClientDlg from the declaration. Add the following after CMemMapCppClientDlg's constructor definition:

CString CMemMapCppClientDlg::m_strContent = "";

Re: variable solution compiles, but I can't get at value:

e40s9-Nov-07 8:15

e40s

9-Nov-07 8:15

I'm confused. There's a constructor in MemMapCppClientDlg.cpp. Do I involve the .cpp in the changes, or is just the MemMapCppClientDlg.h involved?

Re: variable solution compiles, but I can't get at value:

David Crow9-Nov-07 8:27

David Crow

9-Nov-07 8:27

e40s wrote:
Do I involve the .cpp in the changes...

Yes, since you have to do the initialization at file scope.

Re: variable solution compiles, but I can't get at value: [modified]

e40s9-Nov-07 8:39

e40s

9-Nov-07 8:39

It compiles, but I'm not getting anywhere. I'm so lost about following the instructions, I'm going to have to show the code. Here's the whole MemMapCppClientDlg.cpp:

// MemMapCppClientDlg.cpp : implementation file
//

#include "stdafx.h"
#include "MemMapCppClient.h"
#include "MemMapCppClientDlg.h"

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

UINT CMemMapCppClientDlg::UWM_DATA_READY = RegisterWindowMessage(UWM_DATA_READY_MSG); 
/////////////////////////////////////////////////////////////////////////////
// CMemMapCppClientDlg dialog

CMemMapCppClientDlg::CMemMapCppClientDlg(CWnd* pParent /*=NULL*/)
	: CDialog(CMemMapCppClientDlg::IDD, pParent)
{
	m_pszMemMapFileName = _T("Mem_Map_File-{70122C30-0239-4f98-9D21-36885C8A8121}");
}
CString CMemMapCppClientDlg::m_strContent = "";

BEGIN_MESSAGE_MAP(CMemMapCppClientDlg, CDialog)
//[leave the dialog]	ON_WM_WINDOWPOSCHANGING()
	ON_REGISTERED_MESSAGE(UWM_DATA_READY, OnDataReady)
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CMemMapCppClientDlg message handlers

BOOL CMemMapCppClientDlg::OnInitDialog()
{
	CDialog::OnInitDialog();

	return TRUE;  // return TRUE  unless you set the focus to a control
}

LRESULT CMemMapCppClientDlg::OnDataReady(WPARAM, LPARAM) 
{
	HANDLE hMapFile = NULL;
	PVOID pView = NULL;

	hMapFile = OpenFileMapping(FILE_MAP_READ, FALSE, m_pszMemMapFileName);
	if(hMapFile == NULL) {
		MessageBox("Can not open file mapping");
		return 0;
	}

	pView = MapViewOfFile(hMapFile, FILE_MAP_READ, 0, 0, 0);
	if(pView == NULL) {
		MessageBox("Can map view of file");
		CloseHandle(hMapFile);
		return 0;
	}

	LPSTR szContent = reinterpret_cast<LPSTR>(pView);
	int nLen = strlen(szContent);
	CString m_strContent;
	while(nLen > 0) {
		m_strContent += *szContent++;
		--nLen;
	}
	m_strContent += '\0';
	m_strContent.Replace("\n", "\r\n");
////	m_edit.SetWindowText(m_strContent);
    MessageBox(m_strContent);

	if(pView) UnmapViewOfFile(pView);
	if(hMapFile) CloseHandle(hMapFile);

	return 0;
}

CString CMemMapCppClientDlg::GetContent()
{
//    MessageBox(m_strContent, _T("Forget this."));
	return m_strContent;
}

Here's the MemMapCppClientDlg.h:

// MemMapCppClientDlg.h : header file
//

#if !defined(AFX_MEMMAPCPPCLIENTDLG_H__A51F6AF7_F28D_461D_8FB3_EFC7B929D99C__INCLUDED_)
#define AFX_MEMMAPCPPCLIENTDLG_H__A51F6AF7_F28D_461D_8FB3_EFC7B929D99C__INCLUDED_

#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000

/////////////////////////////////////////////////////////////////////////////
// CMemMapCppClientDlg dialog

class CMemMapCppClientDlg : public CDialog
{
// Construction
public:
	static UINT UWM_DATA_READY;
	CMemMapCppClientDlg(CWnd* pParent = NULL);	// standard constructor
	static CString GetContent();
//	CString GetContent();

// Dialog Data
	enum { IDD = IDD_MEMMAPCPPCLIENT_DIALOG };
	// ClassWizard generated virtual function overrides
	protected:

// Implementation
protected:
	// Generated message map functions
	//{{AFX_MSG(CMemMapCppClientDlg)
	virtual BOOL OnInitDialog();
//[leave the dialog]	afx_msg void CMemMapCppClientDlg::OnWindowPosChanging(WINDOWPOS FAR* lpwndpos);
	afx_msg LRESULT OnDataReady(WPARAM wParam, LPARAM lParam);
	DECLARE_MESSAGE_MAP()
	static CString m_strContent;
//	CString m_strContent;

private:
	//enum { m_dwMemFileSize = 2 * 1024 };
	LPCTSTR m_pszMemMapFileName;
};

	#define UWM_DATA_READY_MSG _T("UWM_DATA_READY_MSG-{7FDB2CB4-5510-4d30-99A9-CD7752E0D680}")

//{{AFX_INSERT_LOCATION}}
// Microsoft Visual C++ will insert additional declarations immediately before the previous line.

#endif // !defined(AFX_MEMMAPCPPCLIENTDLG_H__A51F6AF7_F28D_461D_8FB3_EFC7B929D99C__INCLUDED_)

It compiles, but I followed the directions wrong. Nothing's showing up in the message box.

Re: variable solution compiles, but I can't get at value:

e40s9-Nov-07 10:06

e40s

9-Nov-07 10:06

Knowing that a static asssignment can make this work is a lot further along than where I was yesterday (which is a lot farther than where I was the days and and weeks before that.)

I'm sorry I couldn't follow the instructions. My fault. I don't know if my changes to the code are right or wrong. But thanks for the guidance.

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.