C / C++ / MFC

Re: static member variable, dll export and multiple translation units [modified*2]

5-Aug-07 15:43

Here's a problem with static class member:

From DLL A - header:

<br />
class __declspec(dllexport) CLogEntry<br />
{<br />
public:<br />
        ...<br />
<br />
	static CLog* GetSingletonLoggingProvider() { return s_pSingletonLoggingProvider; }<br />
	...<br />
<br />
protected:<br />
         ...<br />
	static CLog * s_pSingletonLoggingProvider;<br />
};<br />

.cpp file:

#include "stdafx.h"<br />
<br />
#include "LogEntry.h"<br />
<br />
CLog * CLogEntry::s_pSingletonLoggingProvider = NULL; << NOTE I need to actually "define" the global variable - that's fine. (so long I don't need to do it multiple times)<br />
<br />
CLogEntry::CLogEntry(int nId, nsCLog::eSeverity nSeverity, char* lpszCode, char* lpszMsg, DWORD dwWin32ErrorCode, CLogEntry * pParent)<br />
{<br />
...<br />
}<br />
... the rest of it...<br />

Now from DLL B (The second dll which is linked to "DLL A")
.cpp file (where CLogEntry is used)

<br />
CLog * CLogEntry::s_pSingletonLoggingProvider = NULL; <br />

<< I need to define this again?? That looks like redundant code to me but if I don't, I'd get the following error.

<br />
Linking...<br />
   Creating library ..\..\bin/XXX.lib and object ..\..\bin/XXX.exp<br />
StdAfx.obj : error LNK2001: unresolved external symbol "protected: static class CLog * CLogEntry::s_pSingletonLoggingProvider" (?s_pSingletonLoggingProvider@CLogEntry@@1PAVCLog@@A)<br />
..\..\bin/XXX.exe : fatal error LNK1120: 1 unresolved externals

So I need to redefine (not "declare") the static member variable in each "Translation Unit"? (separate dll, exe?)

Thanks a bunch!

Mark Salsbery5-Aug-07 16:41

Re: static member variable, dll export and multiple translation units

5-Aug-07 16:41

You can do something like this:

<font size="3">// From DLL A - header:</font>

<font color="Red">#ifdef _BUILDINGDLL
   #define _MY_IMPORTEXPORT __declspec(dllexport);
#else
   #define _MY_IMPORTEXPORT __declspec(dllimport);
#endif</font>

class <font color="Red">_MY_IMPORTEXPORT</font> CLogEntry
{
public:
   ...

   static CLog* GetSingletonLoggingProvider() { return s_pSingletonLoggingProvider; }
   ...

protected:
   ...
   static CLog * s_pSingletonLoggingProvider;
};


<font size="3">// .cpp file:</font>

#include "stdafx.h"

#include "LogEntry.h"

CLog * CLogEntry::s_pSingletonLoggingProvider = NULL; 

CLogEntry::CLogEntry(int nId, nsCLog::eSeverity nSeverity, char* lpszCode, char* lpszMsg, DWORD dwWin32ErrorCode, CLogEntry * pParent)
{
   ...
}
... the rest of it...

Define _BUILDINGDLL (in the compiler preprocessor settings) when building DLL A.
Don't define it when building DLL B

Do NOT redefine s_pSingletonLoggingProvider in DLL B.

Instead use like any other static members (they are imported for external builds, exported when building DLL A):

CLog *pLog = CLogEntry::GetSingletonLoggingProvider();

Make sense?

Mark

Last modified: 2hrs 51mins after originally posted --

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

devvvy5-Aug-07 18:42

Re: static member variable, dll export and multiple translation units

5-Aug-07 18:42

thanks but if I don't guard

<br />
...<br />
class __declspec(dllexport) CLogEntry<br />
{<br />
public:<br />
	...<br />
	static CLog* GetSingletonLoggingProvider() { return s_pSingletonLoggingProvider; }<br />
	<br />
	...<br />
	<br />
protected:<br />
	...<br />
protected:<br />
	...<br />
<br />
	static CLog * s_pSingletonLoggingProvider;<br />
};<br />
<br />
<br />
CLog * CLogEntry::s_pSingletonLoggingProvider = NULL;<br />
#endif<br />

with #ifndef:

<br />
#ifndef _LOGSINGLETON_<br />
#define _LOGSINGLETON_<br />
CLog * CLogEntry::s_pSingletonLoggingProvider = NULL;<br />

then I'd get:

<br />
Linking...<br />
StartupManager.obj : error LNK2005: "protected: static class CLog * CLogEntry::s_pSingletonLoggingProvider" (?s_pSingletonLoggingProvider@CLogEntry@@1PAVCLog@@A) already defined in LogEntry.obj<br />
StartupManager.obj : error LNK2005: "protected: static class CLog * CLogEntry::s_pSingletonLoggingProvider" (?s_pSingletonLoggingProvider@CLogEntry@@1PAVCLog@@A) already defined in LogEntry.obj<br />
StartupManager.obj : warning LNK4006: "protected: static class CLog * CLogEntry::s_pSingletonLoggingProvider" (?s_pSingletonLoggingProvider@CLogEntry@@1PAVCLog@@A) already defined in LogEntry.obj; second definition ignored<br />
   Creating library ..\bin\Utilities.lib and object ..\bin\Utilities.exp<br />
..\bin\Utilities.dll : fatal error LNK1169: one or more multiply defined symbols found<br />
Error executing link.exe.<br />

Should I just include it in ".cpp" instead?

Mark Salsbery5-Aug-07 19:23

Re: static member variable, dll export and multiple translation units [modified*2]

5-Aug-07 19:23

That should have stayed in the CPP, yes. I'll hilight the sample code - I only added the stuff at the top.

Mark

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

devvvy5-Aug-07 22:17

Re: static member variable, dll export and multiple translation units

5-Aug-07 22:17

Thanks very much this is execellent

There're a couple of things I do not understand however.

1. I understand "__declspec(dllexport)", but not sure why we need "__declspec(dllimport)"

2. I do understand precompile directive however:

<br />
#ifdef _BUILDINGDLL<br />
   ...<br />
#else<br />
  ...<br />
#endif<br />

Just not sure why when "Building DLL B" I need to "dllimport" (although I saw it in MSDN)... I don't remember I need to dllimport... just link in project settings and include header file was all I did.

Mark Salsbery6-Aug-07 4:59

Re: static member variable, dll export and multiple translation units [modified*2]

6-Aug-07 4:59

For a true global variable/function you need ONE instance of it.

In your case it was in DLL A.

For other modules to be able to use the globals, you need to export it from
the DLL it exists in and import it in any module that uses it.

By using the preprocessor directives, you can keep the declaration in one header file
instead of two (one for export, one for import). Any changes to the class only have to
be made in one place.

This is how MFC is built, except there's a 3rd option, since MFC can also be built into a
static library.

By the way, you can also import/export individual static members of a class instead of
importing/exporting the entire class. Same method except you put the __declspec()
on the variable declaration instead of the class declaration.

Mark

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

devvvy5-Aug-07 22:24

Re: static member variable, dll export and multiple translation units

5-Aug-07 22:24

Also, I already have the following by ClassWizard when setup the new project:

#ifdef UTILITIES_EXPORTS<br />
#define UTILITIES_API __declspec(dllexport)<br />
#else<br />
#define UTILITIES_API __declspec(dllimport)<br />
#endif<br />

Do I need to do this again for individual class?

devy

Mark Salsbery6-Aug-07 5:01

Re: static member variable, dll export and multiple translation units

6-Aug-07 5:01

devvvy wrote:
Do I need to do this again for individual class?

You can use the same UTILITIES_API macro on a class.

The point is to only export from one module, the module where the actual
static instance(s) exist. All other modules should import.

Mark

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

devvvy6-Aug-07 13:57

Re: static member variable, dll export and multiple translation units

6-Aug-07 13:57

Thanks very much Mark, I been very needy Smile | :)

Mark Salsbery6-Aug-07 14:22

Re: about static libraries

6-Aug-07 14:22

You're welcome! Smile | :)

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

2 dim numbers..

_80865-Aug-07 7:54

_8086

5-Aug-07 7:54

int* pInt = new int[2*3]; 6 elements

So you can access it like pInt[0],1,2,..

now i want to acess it as a 2dim.
for example,
0 1
2 3
4 5

Or

0 1 2
3 4 5

i have declared a pointer like int (*pintPtr)[2][3];

Now how do I assign this to pInt?

something like ,
pintPtr=((int*)[2][3])&pInt;?

This do not work. Please help.

----------------------------
286? WOWW! Blush | :O

Re: 2 dim numbers..

Maxwell Chen13-Aug-07 0:56

Maxwell Chen

13-Aug-07 0:56

void main()
{
	int (*p)[3] = new int[2][3];
	int i, j;
	for(i = 0; i < 2; i++) {
		for(j = 0; j < 3; j++) {
			p[i][j] = i +j;
		}
		printf("\n");
	}
	int (*pX)[3] = p;
	for(i = 0; i < 2; i++) {
		for(j = 0; j < 3; j++) {
			printf("%d ", pX[i][j]);
		}
		printf("\n");
	}
	printf("\n");
	for(i = 0; i < 2; i++, pX++) {
		for(j = 0; j < 3; j++) {
			printf("%d ", (*pX)[j]);
		}
		printf("\n");
	}
	delete [] p;
}

Maxwell Chen

about static libraries

mt_samiei5-Aug-07 4:01

mt_samiei

5-Aug-07 4:01

Dear All
I want to write one DLL. for this purpose, I add one static library to project.
When I compile the program I get following link error.

INK : fatal error LNK1104: cannot open file "nafxcwd.lib"
Error executing link.exe.

But when I add the path of nafxcwd.lib to my lib file paths I get 716 errors.
Do you know how I can remove this problem.
Regards
Monhi

Mark Salsbery5-Aug-07 7:40

Highlight text in static control

5-Aug-07 7:40

What version of Visual Studio?

Mark

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

Legolas655-Aug-07 1:55

Legolas65

5-Aug-07 1:55

I want to highlight part of the text in a static control. I subclassed an existing dialog which can do the trick to one of it's built in controls. However, changing the functionality of the dialog box requires me to do it myself.

The resource code for the control:

CONTROL "", 1027, STATIC, SS_LEFT | WS_CHILD | WS_VISIBLE | WS_GROUP, 21, 103, 190, 69

Spying on the control under normal operation does only reveal the messages WM_GETTEXT,WM_SETTEXT and WM_GETTEXTLENGTH. Although the intended highlighting is actually visible in the control, no other messages are received, which is very confusing to me.

Hamid_RT5-Aug-07 3:49

Hamid_RT

5-Aug-07 3:49

I think if you use of CEdit control is better than to CStatic but if you want on the CStatic you can derived CStatic.

WhiteSky

Legolas655-Aug-07 6:31

Legolas65

5-Aug-07 6:31

Thank you.

I cannot use CEdit, because I use a 3rd party dialog, and the control is already there.
The only thing I can think of now is creating another control right above it, but only as a last resort.

Hamid_RT5-Aug-07 19:02

Hamid_RT

5-Aug-07 19:02

So I think easy way is use of a CStatic derived then you can use of WM_ERASEBKGND or WM_PAINT for show values of control then if you need to highlight a section of text use of SetBkMode (in fact you work with four function SetTextColor/SetBkColor/DrawText/SetBkMode).;)

WhiteSky

henky@online-resource.org

henky@online-resource.org5-Aug-07 23:10

5-Aug-07 23:10

You can create derive class of CStatic and do following:

1. Add in the message map

<br />
   ON_WM_CTLCOLOR_REFLECT()<br />

2. Change Text color in handling function

<br />
   HBRUSH CMyStatic::CtlColor(CDC *pDC, UINT uiCtlColor)<br />
   {<br />
       pDC->SetTextColor(/* Set color what you want */);<br />
       pDC->SetBkMode(TRANSPARENT);<br />
<br />
       return (HBRUSH) GetStockObject(NULL_BRUSH);<br />
   }<br />

Good luck.

Henky Purnawan
henky@online-resource.org

Splitter in MDI Frame

sawerr5-Aug-07 1:10

sawerr

5-Aug-07 1:10

Hi I am trying to split the MDI client window(not child).Like this GUI:
http://www.smidgeonsoft.com/images/PEBrowsePro945x689.jpg
In the left side there is a treeview and the right side there are MDI windows.

I can use splittter in SDI application wtih this code and it can split:

<br />
class CMainFrame : public CFrameWnd<br />
{<br />
  ...<br />
protected:<br />
  CSplitterWnd m_wndSplitter;<br />
  ...<br />
};<br />
  <br />
// SAMPLES\CH03\splitter<br />
// MainFrm.cpp : implementation of the CMainFrame class<br />
<br />
BOOL CMainFrame::OnCreateClient(LPCREATESTRUCT lpcs, <br />
	CCreateContext* pContext) <br />
{<br />
 CSize minWindow(10, 10);<br />
 <br />
  // These variables must both be 1 or 2 for dynamic splitters.<br />
  int nRows = 2, nColumns = 1;<br />
	  <br />
  return m_wndSplitter.Create(this, nRows, nColumns,<br />
	minWindow, pContext);<br />
// <br />
}<br />

But this doent work with MDI application.
I can't divide MDI client window. I tried this:

<br />
BOOL CMainFrame::OnCreateClient(LPCREATESTRUCT lpcs, CCreateContext* pContext)<br />
{<br />
	CSize minWindow(10, 10);<br />
 <br />
  // These variables must both be 1 or 2 for dynamic splitters.<br />
  int nRows = 2, nColumns = 1;<br />
	  <br />
  m_wndSplitter.Create(this, nRows, nColumns,<br />
	minWindow, pContext);<br />
<br />
	return CMDIFrameWnd::OnCreateClient(lpcs, pContext);<br />
}<br />

But it gives run time error about ASSERT(pContext != NULL);

How can i divide MDI client window with splitter so i can insert left side a treeview(static/locked) and in the left side i can show view windows..

I couldnt find the solution.
I am looking for your answers.
Thanks...

Re: Splitter in MDI Frame

sawerr5-Aug-07 6:43

sawerr

5-Aug-07 6:43

I found this(it is what i looked but it is wtl):
http://www.codeproject.com/wtl/mdisplit.asp
But i don't understand the code.

Is there a way to this with MFC?

Re: Splitter in MDI Frame

Mark Salsbery5-Aug-07 12:47