Re: dllimport vs dllexport - C / C++ / MFC Discussion Boards

ns16-Jul-02 8:07

16-Jul-02 8:07

It compiles fine, but crashes when I press the button that executes this snippet:

void CTrain1View::OnToolbarup()
{
//AfxMessageBox("Up pressed");
CToolBar * m_pToolBar;

m_pToolBar = (CToolBar*)GetDlgItem(IDR_MAINFRAME);
m_pToolBar->GetToolBarCtrl().HideButton(ID_TOOLBARDOWN, TRUE);

What am I doing wrong?

Error is memory couldnt be read...

Re: making a toolbar button invisible

Shog⁹16-Jul-02 8:49

Shog⁹

16-Jul-02 8:49

The toolbar is *not* a child of the view, so the line

m_pToolBar = (CToolBar*)GetDlgItem(IDR_MAINFRAME);

isn't going to work. If you used the app wizard to start your program, the CMainFrame class will have a member m_wndToolBar that is the toolbar. You can create an access method for this, or just put your code in CMainFrame to start with (if it's only purpose is doing stuff to toolbars, it probably belongs there anyway).

--------

PMGRE

--Shog⁹ --

Thanks, and also...

ns16-Jul-02 9:07

16-Jul-02 9:07

WHat are the special things to be done to make the toolabr button and a corresponding menu item both run the same code? Would one give the same ID to both the button and the menu item? Is that legal?

Thanks,
ns

Re: Thanks, and also...

Shog⁹16-Jul-02 9:33

Shog⁹

16-Jul-02 9:33

ns wrote:
Would one give the same ID to both the button and the menu item?

Yes.

ns wrote:
Is that legal?

Yes.

--------

PMGRE

--Shog⁹ --

thank you

ns16-Jul-02 9:25

16-Jul-02 9:25

That worked. I tried making a getToolbar() public method in mainframe returning the toolbar object created in CMAinFrame, but it said no copy constructot available. SO I'll put my code in the frame class, though theres data involved that I'm not sure the frame needs to know about...
Thanks a million,
ns

dllimport vs dllexport

Mike Zinni16-Jul-02 4:09

Mike Zinni

16-Jul-02 4:09

I have a 3rd party library that shipped with only the DLL itelf and a header file with function prototypes and constants. All the procedures inside the DLL are declared using the dllimport keyword. Does this mean that I can't dynamically link into this DLL at runtime because none of the functions were exported? I've already written an app that links to this DLL statically, and that works fine, but I'd rather use dynamic linking.

Everything I've read so far points me to the fact that since there isn't a .DEF file, and the functions aren't declared using dllexport, I can't dynamically link to this library. Am I right?

Thanks guys...

-Mike Zinni
email: mzinni@rimail.com
AIM: zin9999

Re: dllimport vs dllexport

Alexandru Savescu16-Jul-02 4:17

Alexandru Savescu

16-Jul-02 4:17

Do you have a lib file? You should be able to link with it.

Best regards,
Alexandru Savescu

Re: dllimport vs dllexport

Mike Zinni16-Jul-02 4:45

Mike Zinni

16-Jul-02 4:45

Yes. I have the .LIB file and the directory is included in my Tools->Options->Directories->Library files settings. I wrote the following code to link to the DLL.

typedef int (CALLBACK* LPOMNICREATEFUNC)(void);

BOOL COmniDoc::LoadOmniLibrary()
{
	m_bOmniLoaded = FALSE;

	m_hOmniLibrary = LoadLibrary("SD2.dll");
	if(m_hOmniLibrary)
	{
		m_bOmniLoaded = TRUE;
		m_lpfnSD_Create = (LPOMNICREATEFUNC)GetProcAddress(m_hOmniLibrary, "SD_Create");
	}
	return m_bOmniLoaded;
}

m_lpfnSD_Create is of type LPOMNICREATEFUNC.

LoadLibrary returns a valid handle, but the m_hlpfnSD_Create variable is set to NULL after the call to GetProcAddress...

-Mike Zinni
email: mzinni@rimail.com
AIM: zin9999

Re: dllimport vs dllexport

Mike Zinni16-Jul-02 5:02

Mike Zinni

16-Jul-02 5:02

OK. Made some progress. I used the Depends tool that comes w/ VC++ and found out that the names of the exported functions are all messed up. That "SD_Create" procedure is actually exported as "_SD_Create@0". Now I'm at least returning a valid function pointer.

Is there any particular reason that the name is changed like that? And secondly, if I didn't use the Depends tool, how in the HELL was I ever supposed to come up with that?

-Mike Zinni
email: mzinni@rimail.com
AIM: zin9999

Re: dllimport vs dllexport

Mike Nordell16-Jul-02 5:24

Mike Nordell

16-Jul-02 5:24

mikez99 wrote:
found out that the names of the exported functions are all messed up. That "SD_Create" procedure is actually exported as "_SD_Create@0".

That's not messed up, that's the usual name mangling taking place for PASCAL (aka __stdcall) calling convention functions.

Re: dllimport vs dllexport

Daniel Lohmann17-Jul-02 14:23

Daniel Lohmann

17-Jul-02 14:23

No, thats not name mangling for C-style __stdcall calling convention, but is the name mangling of the C++ compiler (so called "decorated names").

The reason for this is that C++ supports overloading, but at link time every function identifier needs to be unique. So the C+++ compiler codes the numer and types of the functions arguments into the name and links against this name. The @0 in you case indicates a function without arguments.

Note that decorated names are always used if the functions are exported with __declspec(dllexport).
If possible you should link against the .lib file and so implictly load your DLL. You may also use the VC6 and above delay load feature.

--

Daniel Lohmann

http://www.losoft.de

STL iterators?

Fredrik Skog16-Jul-02 4:00

Fredrik Skog

16-Jul-02 4:00

Why do I get an access violation when I try to get the value of the iterator "it" in this piece of code? When I look at the iterators they have no valid pointers to the strings.

typedef vector<CString*> TFileList;
typedef TFileList::iterator TFileListIt;

CStringList strlistFiles;
fsDlg.SelectFile(&strlistFiles);
int nFiles = strlistFiles.GetCount();

if (nFiles > 0)
{
    int nIndex;
    TFileList FileList(nFiles);

    CString strFileName, strNewFileName;
    POSITION pos;

    // Populate the list with the pointers to the file names.
    for (nIndex = 0; nIndex < nFiles; nIndex++)
    {
        pos = strlistFiles.FindIndex(nIndex);
        FileList.push_back(&strlistFiles.GetAt(pos));
    }

    TFileListIt start, end, it;
    start = FileList.begin();
    end = FileList.end();
    for (it = start; it != end; it++)
    {
        TRACE("> %s\n", **it);   // <-- Access violation!
    }
}

Cheers,
Fredrik

<right>Sonork ID: 100.11430:PhatBoy

"Felix qui potuit rerum cognoscere causas."

Re: STL iterators?

Alexandru Savescu16-Jul-02 4:08

Alexandru Savescu

16-Jul-02 4:08

Try *(*it)? (Just guessing Smile | :)

).

Best regards,
Alexandru Savescu

Re: STL iterators?

Fredrik Skog16-Jul-02 4:12

Fredrik Skog

16-Jul-02 4:12

The problem is that my vector seems to be empty, even though I am filling it with valid pointers. Frown | :(

Cheers,
Fredrik

<right>Sonork ID: 100.11430:PhatBoy

"Felix qui potuit rerum cognoscere causas."

Re: STL iterators?

Alexandru Savescu16-Jul-02 4:22

Alexandru Savescu

16-Jul-02 4:22

Did you call size() to see if it is empty?

Best regards,
Alexandru Savescu

Re: STL iterators?

Fredrik Skog16-Jul-02 4:30

Fredrik Skog

16-Jul-02 4:30

size() returns 8, but I have added 4 pointers to the vector. Confused | :confused:

I have noticed that the vector elements does not point to m_pchData of the string list elements I am using, but to some other address.
_First and _Last of the vector are updated when adding to the vector.

Cheers,
Fredrik

<right>Sonork ID: 100.11430:PhatBoy

"Felix qui potuit rerum cognoscere causas."

Re: STL iterators?

Alexandru Savescu16-Jul-02 4:35

Alexandru Savescu

16-Jul-02 4:35

Try not to store pointers, store CStrings directly. There is not much of a performance differnce since the CString does not get copied, its reference is increased.

Best regards,
Alexandru Savescu

Re: STL iterators?

Fredrik Skog16-Jul-02 4:42

Fredrik Skog

16-Jul-02 4:42

Nah, didn't work either. The push_back seems broken...

Cheers,
Fredrik

<right>Sonork ID: 100.11430:PhatBoy

"Felix qui potuit rerum cognoscere causas."

Now I got it!!!

Alexandru Savescu16-Jul-02 4:43

Alexandru Savescu

16-Jul-02 4:43

It's this line:

Fredrik Skoog wrote:
TFileList FileList(nFiles);

This creates nFiles items initially empty and I guess NULL pointers. That's why you had 8 items, because 4 have already been created.

You shoud use:

TFileList FileList;
FileList.reserve (nFiles);

reserve allocates enough space, but does not create any items.

Best regards,
Alexandru Savescu

Re: Now I got it!!!

Fredrik Skog16-Jul-02 4:48

Fredrik Skog

16-Jul-02 4:48

Yep, that's it. Thanks a million!
I think I'll have to hit the books now Blush | :O

Cheers,
Fredrik

<right>Sonork ID: 100.11430:PhatBoy

"Felix qui potuit rerum cognoscere causas."

CFile access

Raphael Kindt16-Jul-02 3:28

Raphael Kindt

16-Jul-02 3:28

Hi...

I've a class MyClass which contain a member CFile m_MyFile.
I want to pass this file (open) to another class CMyOtherFile derived from CFile...
I tested while passing the handle of m_MyFile but that doesn't work (and it's not recommanded)...

Anybody can help me???

Thanks...

Hello World!!! Smile | :)

from Raphaël

Re: CFile access

Fredrik Skog16-Jul-02 3:47

Fredrik Skog

16-Jul-02 3:47

If I understand you correctly, I think you should rethink your design strategy.
I think it might be better to pass the file name if possible.

Cheers,
Fredrik

<right>Sonork ID: 100.11430:PhatBoy

"Felix qui potuit rerum cognoscere causas."

Re: CFile access

Raphael Kindt16-Jul-02 4:23

Raphael Kindt

16-Jul-02 4:23

Of course... I've found another solution... A better solution...
Thanks...

Hello World!!! Smile | :)

from Raphaël

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