Re: strange linking error with operator overloading [modified] - C / C++ / MFC Discussion Boards

Syouki_kou3-Jul-06 20:38

3-Jul-06 20:38

Thanks for your help, whitesky!
But I wonder if you really understand what I want to realize!
I just want to know the status of CD-ROM, it is opened or closed?
The MCI command can't work at all, I tried it before, and WM_DEVICECHANGE message also can't work. And I tried MMC command(APSI programming),but it can only work on DVD-ROM, do not work on CD-ROM! That's my trouble.

My original purpose is that if you right click the CD/DVD-ROM icon, the eject menuitem can take a little change for it can change to "Insert" if the door is already opened, and back to "eject" if the door is closed. For this, I must know the status of the door, it is closed or open?

One day a pretty girl asked me: "Do you think you are handsome?"."I don't think so!" She gave a slap in my face:"Why lying?"

strange linking error with operator overloading

George_George2-Jul-06 21:27

George_George

2-Jul-06 21:27

Hello everyone,

I am meeting with a strange linking error regarding to operator overloading. I am creating a C++ static lib, and then linking it with a C application. Here is the error message and source codes,

I am using adapter.cpp, adapter.h, foo.cpp and foo.h to create a static lib called foo.lib, then link it with a C application (goo.c). There is no problem to generate the static lib foo.lib.

Any comments to solve this link error?

<br />
error LNK2019: unresolved external symbol "private: class FooNameSpace::Foo __thiscall FooNameSpace::Foo::operator=(long)" (??4Foo@FooNameSpace@@AAE?AV01@J@Z) referenced in function "private: __thiscall FooNameSpace::Foo::Foo(<br />
long)" (??0Foo@FooNameSpace@@AAE@J@Z)<br />
<br />
fatal error LNK1120: 1 unresolved externals<br />

adapter.cpp

<br />
#include "adapter.h"<br />
#include "foo.h"<br />
<br />
using namespace FooNameSpace;<br />
<br />
void compute(void)<br />
{<br />
	Goo g;<br />
	g.computeFoo();<br />
}<br />

adapter.h

<br />
#ifdef __cplusplus<br />
extern "C" {<br />
#endif<br />
<br />
void compute (void);<br />
<br />
#ifdef __cplusplus<br />
}<br />
#endif<br />

foo.cpp

<br />
#include "foo.h"<br />
<br />
using namespace FooNameSpace;<br />
<br />
Foo Foo::operator=(long value)<br />
{<br />
  this -> value = value;<br />
  return (*this);<br />
}<br />

foo.h

<br />
namespace FooNameSpace<br />
{<br />
	class Foo<br />
	{<br />
<br />
	private:<br />
		long value;<br />
  <br />
		 Foo (long value) { (*this) = value; }<br />
		 inline Foo operator= (long value);<br />
		 friend class Goo;<br />
  };<br />
<br />
	class Goo<br />
	{<br />
	public:<br />
		void computeFoo()<br />
		{<br />
			Foo foo = Foo(0L);<br />
		}<br />
  };<br />
}<br />

goo.c (link with foo.lib)

<br />
#include "adapter.h"<br />
#include "windows.h"<br />
<br />
int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,<br />
                    LPWSTR lpCmdLine, int nCmdShow)<br />
{<br />
	compute();<br />
	return 0;<br />
}<br />

thanks in advance,
George

Re: strange linking error with operator overloading

Viorel.2-Jul-06 21:40

Viorel.

2-Jul-06 21:40

I think no error will be generated if you:

remove the inline keyword from the declaration of Foo::operator =;
or, move the implementation of Foo::operator = from foo.cpp to foo.h file;
or, place the implementation of Foo::operator = function inside the Foo class.

I hope it helps.

Re: strange linking error with operator overloading

George_George2-Jul-06 21:47

George_George

2-Jul-06 21:47

Hi Viorel!

Your method is so magic and it works! What is the reason of my linking error and why your method works?

regards,
George

Re: strange linking error with operator overloading

Viorel.2-Jul-06 22:02

Viorel.

2-Jul-06 22:02

As I know, when we work with inline functions, then the body of such items must be provided in .h files, not in .cpp ones. This is because the compiler needs the source code of such functions in order to insert them into compiled code, thus making them "inline".

If we implement a function in a .cpp file, then the compiler makes a binary .obj or .lib file, and the source code is lost. Therefore the compiler will be only able to generate a call to such functions, but not make them inline.

This is also true for template classes and template functions -- they must be delivered in header files. (For instance see STL).

However, it seems that future compilers will allow implementation of inline and template items in .cpp files.

Re: strange linking error with operator overloading

George_George2-Jul-06 23:37

George_George

2-Jul-06 23:37

Thank you Viorel!

Viorel. wrote:
As I know, when we work with inline functions, then the body of such items must be provided in .h files, not in .cpp ones. This is because the compiler needs the source code of such functions in order to insert them into compiled code, thus making them "inline".

It should be the linker not the compiler to insert implementations into compiled code, right?

Viorel. wrote:
If we implement a function in a .cpp file, then the compiler makes a binary .obj or .lib file, and the source code is lost. Therefore the compiler will be only able to generate a call to such functions, but not make them inline.

Do you mean we need to insert the source codes of inline function into the modules which invoke inline functions?

I think ordinary function (non-inline function) does not need to insert source codes into the modules which invokes the ordinary function, right? And what did the linker/compiler do when dealing with ordinary function in the same situation?

regards,
George

Re: strange linking error with operator overloading

Viorel.3-Jul-06 0:08

Viorel.

3-Jul-06 0:08

In my vision, when we call an inline function from 100 different places, the body of function is inserted in each such a place, and then the entire code is compiled. Only compiler can do this task. That’s why we need to supply the source code of inline function to the compiler.

The linker cannot do such task. Linker only assembles compiled code (.obj and .lib files).

In case of non-inline functions, they are compiled once into an .obj or .lib file. In the modules, to the compiler we need to supply only the declaration of such functions. If we call such function from 100 different places, then the compiler will generate a CALL microprocessor instruction in each place, but without an address. The address will be inserted later by the linker.

That’s my opinion.

Re: strange linking error with operator overloading [modified]

George_George3-Jul-06 0:33

George_George

3-Jul-06 0:33

Thank you Viorel!

If it is the compiler who inserts source codes implementation of an inline function into the place when we invoke the function, I think there should be compiling errors other than link errors in my situation, right? But why when I build the foo.cpp, foo.h, adapter.cpp and adapter.h into a static library (foo.lib), there is no error (I think at this time, the compiler should insert the source codes implementation of inline method into the places where inline methods are invoked)?

But the errors are reported when we link the static library into an executable file?

regards,
George

-- modified at 6:34 Monday 3rd July, 2006

Re: strange linking error with operator overloading

Viorel.3-Jul-06 1:58

Viorel.

3-Jul-06 1:58

I think when you are building the library file, since the Foo::operator = function was declared inline, the compiler does not generate an entry for it, i.e. this function is not exported. The compiler does not know that you are going to use it in another place. (I suppose the list of exported functions can be checked with dumpbin utility).

I think when compiler builds a file in which an inline function is called, but no body of this function is available, then the compiler treats this as a non-inline function, and expect it to be implemented somewhere. (Maybe it would be better to show a warning message here).

Because the linker was not yet invoked during compilation of your static library, no problems occur yet.

Errors occur later when the linker cannot link your module because of missing external function.

Re: strange linking error with operator overloading

George_George3-Jul-06 2:45

George_George

3-Jul-06 2:45

Thank you Viorel!

Viorel. wrote:
I think when you are building the library file, since the Foo::operator = function was declared inline, the compiler does not generate an entry for it, i.e. this function is not exported. The compiler does not know that you are going to use it in another place. (I suppose the list of exported functions can be checked with dumpbin utility).

Why inline function is not treated as exported? I think foo.cpp exports the inline operator overloading function by the following statement (the first line of function definition),

<br />
Foo Foo::operator=(long value)<br />

Maybe I am wrong. Could you explain how (in what form) an function can be exported (in my previous comprehension, I think non-static function, which means not locally used function, like the above function, is exported automatically)?

Viorel. wrote:
I think when compiler builds a file in which an inline function is called, but no body of this function is available, then the compiler treats this as a non-inline function, and expect it to be implemented somewhere. (Maybe it would be better to show a warning message here).

Do you mean the when the compiler builds foo.cpp or adapter.cpp or goo.cpp? Confused. Smile | :)

regards,
George

Re: strange linking error with operator overloading

Viorel.3-Jul-06 3:35

Viorel.

3-Jul-06 3:35

A function is "exported" from .obj or .lib binary files means that there is an address which points to the beginning of the compiled function. This address is used by linker to generate the CALL microprocessor instructions. If a function is marked as inline, then no such address is stored in the .obj or .lib file, because it is supposed that the body of the function will be entirely inserted by compiler instead of CALL instruction.

It seems that only non-inline and not-static functions are exported by .obj and .lib files.

George_George wrote:
Do you mean the when the compiler builds foo.cpp or adapter.cpp or goo.cpp?

Yes.

Re: strange linking error with operator overloading [modified]

George_George3-Jul-06 4:08

George_George

3-Jul-06 4:08

Thank you Viorel!

Viorel. wrote:
A function is "exported" from .obj or .lib binary files means that there is an address which points to the beginning of the compiled function. This address is used by linker to generate the CALL microprocessor instructions. If a function is marked as inline, then no such address is stored in the .obj or .lib file, because it is supposed that the body of the function will be entirely inserted by compiler instead of CALL instruction.

It seems that only non-inline and not-static functions are exported by .obj and .lib files.

I think in my case, in foo.cpp, since it includes foo.h, in which operator =() is declared as inline function, so it is not exported, right?

Viorel. wrote:
George_George wrote:
Do you mean the when the compiler builds foo.cpp or adapter.cpp or goo.cpp?

Yes.

Confused. Do you mean them all or one of them? I think it should be adapter.cpp, right?

regards,
George

-- modified at 10:09 Monday 3rd July, 2006

Re: strange linking error with operator overloading

Viorel.3-Jul-06 4:24

Viorel.

3-Jul-06 4:24

George_George wrote:
I think in my case, in foo.cpp, since it includes foo.h, in which operator =() is declared as inline function, so it is not exported, right?

Yes.

George_George wrote:
Confused. Do you mean them all or one of them? I think it should be adapter.cpp, right?

Yes.

Re: strange linking error with operator overloading

George_George3-Jul-06 17:12

George_George

3-Jul-06 17:12

Cool, Viorel!

You have answered my question.

regards,
George

split window

ashish dogra2-Jul-06 21:27

ashish dogra

2-Jul-06 21:27

// the following function is created by (step 4) of the MFC AppWizard
// when you select Use split window from the Windows Style tab of the
// Advanced Options dialog

BOOL CMainFrame::OnCreateClient(LPCREATESTRUCT /*lpcs*/,
CCreateContext* pContext)
{
return m_wndSplitter.Create(this,
2, 2, // TODO: adjust the number of rows, columns
CSize(10, 10), // TODO: adjust the minimum pane size
pContext);
}

i use this code but it does not show mw the split window plz help me how can i see split window

Ashish Dogra
MCA
Noida

Re: split window

Weiye Chen3-Jul-06 0:06

Weiye Chen

3-Jul-06 0:06

ashish dogra wrote:
i use this code but it does not show mw the split window plz help me how can i see split window

The split window is there, just that the default size makes it somehow hidden. Check the scrollbars in your window. Hover your mouse over the left edge (horizontal scrollbar) or top edge (vertical scrollbar) of the scrollbar and you should see your cursor changes. Now drag your splitted window out.

Use CDHtmlDialog in statically linked MFC DLL

rockryan2-Jul-06 21:27

rockryan

2-Jul-06 21:27

Hi,
I use a statically linked MFC exe load a statically linked MFC DLL, and careate a CDHtmlDialog in that DLL,
I already add below code to solved original when create CDHtmlDialog will crash problem successfully,

AFX_MANAGE_STATE(AfxGetStaticModuleState());
::OleInitialize(NULL);
AfxEnableControlContainer();

but now when I use it's member function, ex:GetDHtmlDocument
it'll crash,

I already add AFX_MANAGE_STATE(AfxGetStaticModuleState()); to the DLL's each function still have same problem

what else should I add?

Thanks!!

Re: Use CDHtmlDialog in statically linked MFC DLL

Hamid_RT2-Jul-06 22:31

Hamid_RT

2-Jul-06 22:31

GetDHtmlDocument retrieves IHTMLDocument2 from html document now whats your problem

whitesky

how to transfer data between the tabs

kotiramkoteswararao2-Jul-06 20:44

kotiramkoteswararao

2-Jul-06 20:44

Hi,

I have created a tab control. i have placed some controls on first tab page(TAB1). And some another controls on second tab page(TAB2). I want to send the data from tabpage1 to tabpage2.

How can do it. plz suggest any solution?

with regards,
Koti

Re: how to transfer data between the tabs

capricious_0012-Jul-06 22:39

capricious_001

2-Jul-06 22:39

Not sure what data you would want to send, but you can use pipes to exchange data. Otherwise if its globally stored data in variables you can update the variables then you can have your own user defined windows messages and send messages to and from each tab window as shown below.

#define UWM_TABPAGE1 WM_APP+1

...


SendMessage(tab1_hwnd, UWM_TABPAGE1, NULL, NULL);

GEetting Socket Notification Sink Error

zahid_ash2-Jul-06 20:31

zahid_ash

2-Jul-06 20:31

HI,
I am getting Socket Notification Sink error, How can I eliminate this.

2ndly , when I use Spy++ to view Process I saw one process under my application node with text "Socnet Notifiaction Sink " why it is there

Thanks

Regards.

splitter window

ashish dogra2-Jul-06 19:50

ashish dogra

2-Jul-06 19:50

hi all
plz help me
i want to know that some time i make an application (SDI)
in which i use CView Class now i want to use csplitterwnd or other class then how i use those
as i want to make a splitter window

plz show me some example

Ashish Dogra
MCA
Noida

Re: splitter window

Abhi Lahare2-Jul-06 20:03

Abhi Lahare

2-Jul-06 20:03

From MSDN:

// the following function is created by the MFC Application Wizard <br />
// when you select Split window from the User Interface Features tab: <br />
<br />
BOOL CMainFrame::OnCreateClient(LPCREATESTRUCT /*lpcs*/, <br />
      CCreateContext* pContext)<br />
{<br />
   return m_wndSplitter.Create(this,<br />
         2, 2,               // TODO: adjust the number of rows, columns<br />
         CSize(10, 10),      // TODO: adjust the minimum pane size<br />
         pContext);<br />
}

Re: splitter window

ashish dogra2-Jul-06 20:31

ashish dogra

2-Jul-06 20:31

sir i have tried this what as it is sdi application when irun this it does not split that frame window

Ashish Dogra
MCA
Noida

Re: splitter window

Abhi Lahare2-Jul-06 23:41

Abhi Lahare

2-Jul-06 23:41

try this:

BOOL CMainFrame::OnCreateClient(LPCREATESTRUCT lpcs, CCreateContext* pContext)
{
// TODO: Add your specialized code here and/or call the base class
BOOL res = m_splilter.CreateStatic(this,2,1);
m_splilter.CreateView(0,0,RUNTIME_CLASS(CsplView),CSize(0, 200), pContext);
m_splilter.CreateView(1,0,RUNTIME_CLASS(COtherView),CSize(200, 200), pContext);
return TRUE;
}

Where CsplView is a default view class generated by Wizard
and COtherView is class derived from Cview.

Hope these help.

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