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Hi guys, I have a question about function pointer passsing. The following
code is the beginnings of a Win32 app.
main.cpp<br />
<br />
#include "windows.h"<br />
#include "classOne.h"<br />
<br />
<br />
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)<br />
{<br />
return 0;<br />
}<br />
<br />
<br />
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,<br />
LPSTR lpCmdLine, int nCmdShow)<br />
{<br />
Nothing n(WndProc);<br />
<br />
return 0;<br />
}
As you can see, all I'm trying to do is pass the WndProc function as
a parameter to the constructor of a class called Nothing.
Nothing.h<br />
<br />
#include "windows.h"<br />
<br />
class Nothing<br />
{<br />
public:<br />
Nothing(WNDPROC wndProc);<br />
};
Nothing.cpp<br />
<br />
#include "classOne.h"<br />
Nothing::Nothing(WNDPROC wndProc)<br />
{<br />
int kk = 0;<br />
}
Well my question is, why is it that when I step into the constructor of
the "Nothing" class, wndProc appears to have a different address than
the one I passed in? For the life of me I can't see why this is the case as
WndProc is typedef'd as LRESULT (*WNDPROC)(HWND, UINT, WPARAM, LPARAM)
I'm sure that if I go any further, I'm likely to get an error for example,
when I use that address to initialize and register a window class.
Any hints??
Woke up this morning...and got myself a blog
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What you are passing here is a pointer to a function. The name of a function is always it's address, like using the address-of operator automatically. This address, of course, refers to the starting point of the function in memory.
However, in this case, the constructor seems to create a copy of the function, and move it into a seperate place in memory. I do not know why it does this, but calling the function does work properly. Here is the code fragment with which I tested it.
#include <iostream>
using namespace std;<DIV>
typedef void (*ptrFunc1)(int, int, double, double);<DIV>
void MyFunction( int a, int b, double c, double d )
{
cout << "Inserted: " << a << " " << b << " " << c << " " << d << "\n\n";
}<DIV>
class Nothing
{
public:
Nothing(ptrFunc1 func1);
};<DIV>
Nothing::Nothing(ptrFunc1 func1)
{
int a = 10;
int b = 20;
double c = 30;
double d = 40;<DIV>
func1(a, b, c, d);
}<DIV>
int main(void)
{
Nothing MyNothing(MyFunction);
}Although whilst in debugging, the addresses of MyFunction and func1 are different, and even (*func1) points to a different place than MyFunction, the code calls MyFunction properly through the func1 function pointer, and the text gets printed out correctly.
I see no reason why your implementation would not work properly as well. The reasons of why the memory locations are different is unknown to me, it would require some more work to determine it. I even tested it by creating two objects of class Nothing. In that case, the func1 pointed to the same location in both cases.
So, although I don't understand why it happens, the code works, so you shouldn't have anything to worry on that part 
-Antti Keskinen
----------------------------------------------
The definition of impossible is strictly dependant
on what we think is possible.
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i have two projects ,, one MFC dialoged base and other is WIN32
i want to place them in 1 workspace..
and also want to communicate between these 2 projects classess.
for example .. in MFC i have created a socket by CSocket class ,, now i want to this socket in my WIN32 application ,, how can i do it .
Plz help me its urgent
thanx
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Having two projects in a single workspace is easy.
Just open the workspace you want to have both projects in, then go right-click on the workspace name and add an existing item/project to workspace. Remember to take the tick off from 'Dependency of' radio box if it is checked.
As the two projects are seperate applications and thus run on seperate processes, the only feasible solution is to use a named pipe between them. Have the MFC application create a named pipe, and write it's data in there. Then signal the Win32 application to open the pipe and read data from there. Remember that in this case, you cannot pass for example a pointer to the CSocket class through the pipe to the other application, as this pointer is no longer valid when it leaves the context: using it will cause a protected-mode memory failure, or in Windows 95/98, the notorius Blue Screen of Death.
If you want to share viable data, such as pointers to classes or data, between the two applications, then you must run them under the same process space, on seperate threads. The MFC program can create a new thread, and hit the Win32 application running there. Then it is just a matter of cross-thread messaging to pass stuff between them. Naturally, a named pipe is a useful solution in this case as well.
Even simpler solution to use the Win32 application, you can call the LoadLibrary function, get the address of the starting point function (WinMain) from it, then call it manually. This will load the application into the MFC-program's process space and execute it's WinMain function, which simulates running the program. In this case, of course, the WinMain function must be exported from the executable and a definition file is required.
There are a few articles available here on CodeProject about cross-thread and inter-process communication. See this area[^] for some examples.
-Antti Keskinen
----------------------------------------------
The definition of impossible is strictly dependant
on what we think is possible.
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To have two projects in one workspace, simply "add existing project" from context menu on workspace (as I remember).
If you want to use the other project, you can import/export some data. In case of socket it will be more difficult, cause you will not be able to debug two projects from one workspace in one vc at once
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I have a sound data in array of 1MB ,
how can i send it through CSocket class ...
Is there any type ast needed.. if yes then how.
will it loose data or not..
thanx
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Check out this link for a reference to the API.
To answer your question, if you create the socket with the SOCK_STREAM flag, then the TCP will be used and you will not lose any data since TCP is a reliable transport. However, if you want a potential speed-up in send times (at the risk of losing data), create the socket with the SOCK_DGRAM flag to create a UDP connection.
The Send function takes data in the form of a void* (see above link for further reference).
--Dean
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I have a program that has a list view on a dialog. I have a separate thread from a DLL go out and get some data (from Outlook Express in this case). The data ends up begin returned OK, but wehen I try to add the data to the list control, the data keeps getting put in the first entry. I am using InsertItem(-1, NULL) to insert the data into the list control. The funny thing is that this is working in other modes, just not this one. Anyone have any ideas?
By the way, the app consists of a main EXE, which calls an MFC DLL (which holds the UI). The UI DLL in turn uses an extension DLL to save and load data. The UI DLL also calls an MFC DLL to handle the import of the data (no UI).
Any help would be greatly apprecaited.
[EDIT]
By the way, this only happens on onc test system with Windows 98. Other WIndows 98 systems seem to work fine.
[/EDIT]
Regards,
Brigg Thorp
Software Engineer
Timex Corporation
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Yeah, I remember that problem. It seems to be special Win98 index behaviour. I circumvented it by simply using:
int x = 0;
while(<cond>)
{
InsertItem(x, "");
x++;
}
BTW I'm not sure it's safe to use NULL as text either
Nick
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Is there any way to force the title of a MDI app to display what you want.. Example lets say I want my MDI title to all ways read "Rob".
When I open new documents or switch between docs I dont want the title to say "My App - [Rob]" I only want to see Rob.
I kind of remember seeing a flag you can set in PreCreateClient that disables this auto-naming feature. But I cant figure it out for the life of me.. 
Any Ideas?
Rob
Whoever said nothing's impossible never tried slamming a revolving door!
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Just incase anyone else forgets the darn flag its FWS_ADDTOTITLE
Rob
Whoever said nothing's impossible never tried slamming a revolving door!
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Here's the deal, I have a test class that I am working on and everything seems to be in order, yet I am struck with a link error for every time I use this class (I am using this class from my main() function in main.cpp).
-I have added both the header and source file for the class into my VC++.NET 2003 project.
-Within my main.cpp, is my main() function. At the top of this file, I have the header file to my class included.
-I have my class header file included at the top of the class's implementation/source file.
-The strange thing is when I ALSO include the implementation (.cpp) file at the top of the main.cpp file, it compiles and links with no problems, but I shouldn't have to be including both files.
What am I doing wrong? Or has my VC++.NET 2003 just gone crazy? 
Any points into the right direction would be greatly appreciated.
Happy Programming!
WWW::CodeProject::BNEACETP
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It's tough to figure out this problem without details about your header/implementation and what the link error is.
Is your class a template? If so, then the implementation must be defined in the header.
- Mike
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Michael Imamura wrote:
Is your class a template?
Yes it is.
Thanks for the info about template class inclusions. I will simply add the implementation code to the header file then. Once again, thanks. 
Happy Programming!
WWW::CodeProject::BNEACETP
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Hi,
I have a weird linking error happening in my C++ DLL project. In VS.Net 2003, when I compile my dll in release mode, I get the normal "linking... Creating library c:\some_path\blah.lib", but if I do the same in debug, I get "linking..." but the .lib doesn't get created/updated. Other than that, it seems to compile file. No errors get generated.
I've checked the settings between both modes, and I can't see anything different between them.
If I do a "rebuild all" it does update the .lib, but not if I just modify a file and compile the project. I don't want to "rebuild all" everytime I want to test a change. Any ideas?
Thanks!
DJCC
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I've noticed the same thing too. This is just a guess, but I think it's probably fine if the .lib file isn't updated. Basically the .lib file provides the interface for the DLL that you will link against in some other program. So, if you just update the implementation (rather than the function signatures) there is no reason to update the lib file, because the interface to the DLL remains the same.
Again, I'm not 100% sure about that so someone correct me if I'm wrong, but I think you'll be fine linking against the .lib file even if it's not updated.
--Dean
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The real problem I have with this is that when I start changing classes around (adding/removing methods), whenever I stop to and continue from a breakpoint, I get "runtime check failure #0" errors. If I rebuild, which updates the .lib file, I don't get these errors.
DJCC
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See the project settings that you have the 'Import Library' option set under 'Linker->Advanced'. This controls the creation of the .lib file.
Also, you must have a module definition file in your project. If this file doesn't exist, then the compiler/linker creates the export library only if you have dllexport-declarations inside the code files. This might result in incorrect behaviour if those functions which you add to the classes are not exported. The module definition file is not required to export any symbols. All that needs to be there is a line 'LIBRARY your_dll_name_here'.
-Antti Keskinen
----------------------------------------------
The definition of impossible is strictly dependant
on what we think is possible.
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I create a CF_HDROP data-block representing the file-names of the files i'm dragging.
Everything works great except for dragging into the Recycle-Bin.
I'v read that I need to modify the SetData implementation of my IDataObject so that it accepts the CFSTR_TARGETCLSID format.
Apparently the recycle-bin performs a SetData on me (my IDataObject) telling me that i'm dropping things into the recycle.
The thing is, I'm not sure what to do with this information...
The data is cached into my data-object but nothing happens.
Funny thing is that if I debug the code and take a several second pause when I get this SetData code, the files do get thrown into the recycle-bin
so, can someone advise ?
p.s - regardless of thigs, dropping into the recycle-bin leaves me addref'd for some reason (m_dwRef in MFC)... which forces me to check it and perform an ExternalDisconnect when this happens, doesn't sound like the right thing to do...
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Hi
i m building voice conversation application .
now i want to send SoundBuffer (of Directx) via Socket to my server.
how can i send it .. will it be lose its data .
plz help mee
thanx
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One solution is winsock. For data reliability, I recommend TCP.
Kuphryn
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Hi!
I'm using ShellExecute to open a link in the browser. If there is a browser instance already running then it will show the link! How can I force the link to be showned in a new instance??
Thank you
Artur Jales Moreira
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Post the code you pass into ShellExecute(). One possible solution is CreateProcess().
Kuphryn
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Try adding -new after iexplore.exe in the ShellExecute parameters. There is a list of command line options here[^].
Heard in Bullhead City - "You haven't lost your girl -
you've just lost your turn..." [sigh] So true...
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