Newbie: Can I do this? - C / C++ / MFC Discussion Boards

Steve Thresher4-Aug-04 6:03

4-Aug-04 6:03

Is the following legal C++ code?

try
{
    char s[10]="Error";
    <br>
    if (some condition)
        throw s;
}
catch (const char *s2)
{
    OutputDebugString(s2);
};

From what I've read I would expect the catch block to receive a pointer to stack memory thats no longer reserved for the variable s. Am I correct?

Systems AXIS Ltd - Software for Business ...

Re: try/catch Variable Scope Question

Nitron4-Aug-04 7:36

Nitron

4-Aug-04 7:36

Steve Thresher wrote:
Is the following legal C++ code?

It appears that throw throws a copy of the data, thus preserving the scope. It is the same concept as constructing an exception in your code and throwing it.

~Nitron.

ññòòïðïðB A start

Re: try/catch Variable Scope Question

palbano4-Aug-04 7:49

palbano

4-Aug-04 7:49

Nitron wrote:
It appears that throw throws a copy of the data

Well it of course copies the char* variable but the caught variable contains the same memory address as the thrown variable. So the memory is not copied. Don't know if that is what you meant. Confused | :confused:

"No matter where you go, there your are." - Buckaroo Banzai

-pete

Re: try/catch Variable Scope Question

Steve Thresher4-Aug-04 10:07

Steve Thresher

4-Aug-04 10:07

If you're dealing with objects a copy is made when the object is thrown (using the copy constructor or a shallow copy if a copy constructor is not avaiable) and then the original is destroyed at the end of the try block. When it comes to strings the compiler only knows the address of the string so no copy can be made.

Systems AXIS Ltd - Software for Business ...

Re: try/catch Variable Scope Question

palbano4-Aug-04 7:43

palbano

4-Aug-04 7:43

That is not my understanding. The stack will not begin to unwind until after the exception handler returns.

"No matter where you go, there your are." - Buckaroo Banzai

-pete

Re: try/catch Variable Scope Question

Tim Smith4-Aug-04 15:26

Tim Smith

4-Aug-04 15:26

If it works, it works due to something that is implementation specific.

In general, I would beat people who made code that depended on that.

Tim Smith

I'm going to patent thought. I have yet to see any prior art.

Re: try/catch Variable Scope Question

Ryan Binns4-Aug-04 18:46

Ryan Binns

4-Aug-04 18:46

It will probably work, but shouldn't really be used. Instead, you could throw an integer index into an array of strings stored elsewhere, or allocate memory for the string and throw it, then free it in the catch() block.

Ryan

"Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late" John Nichol "Point Of Impact"

Newbie: Can I do this?

cgriffin4-Aug-04 5:52

cgriffin

4-Aug-04 5:52

I want to program a DLL that would have three entry points. Initialize, DoDialog and Terminate. The Initialize would have a parameter that is a callback into the calling application. DoDialog would have a parameter that would be a Handle to a block of data. When called DoDialog would bring up a dialog and return when the dialog is finished. The data would be modified by the dialog. Terminate would just release things that were allocated in Initialize. So is this possible? Should I do this in MFC, .NET, something else? I also have a fair amount of non-UI C++ code that need to be ported for this dialog as well.

Re: Newbie: Can I do this?

palbano4-Aug-04 7:16

palbano

4-Aug-04 7:16

cgriffin wrote:
Can I do this?

I have no way of knowing that.

palbano wrote:
Can it be done?

Sure Big Grin | :-D

"No matter where you go, there your are." - Buckaroo Banzai

-pete

Re: Newbie: Can I do this?

digwizfox4-Aug-04 7:31

digwizfox

4-Aug-04 7:31

Sounds reasonable. You can program a DLL to do many things for you as long as you define a good interface. DLLs can contain classes and/or global functions that can be exported so that an application project can link to it. I like to think of DLLs kind of like how I think of classes. You figure out what you want it to do; what kind of logic/common code you want in it and design a good user interface so that other projects can link to the functions and/or classes.

We have a main app project that links to MFC extension DLLs. Use the wizard to create your ext DLLs and it is very simple. In some cases our MFC extension DLLs export class definitions (such as common dialogues). Then the main app can use #include "TheDialogueHeader.h" and then instantiate the dialogue like any other MFC class and implement a modal or modeless dialogue.

We also have DLLs that export a thread function that the application can link to and call by passing the function pointer to AfxBeginThread. Then you have a DLL with a main function that is a thread that will execute along with all of the threads in the Main App project. So your Initialize() func could be a thread or just a function that can be called and will return when finished. If it is a thread, then use the terminate function to implement the signaling logic that will cause the thread(s) in the DLL to terminate for a clean exit.

There are lots of ways to do it but what you are describing seems like a reasonable thing to do. The possibilities are endless and there are many different ways of organizing the code within your DLL. Just like a class, you can have global functions in the DLL or classes that are not exported (private to the rest of the world) that are called by the exported functions/classes (public to the world); and so on and so on.

Have fun!
Shawn

Re: Newbie: Can I do this?

cgriffin4-Aug-04 7:45

cgriffin

4-Aug-04 7:45

Thanks for your reply. I was afraid to add too much to the first post so I left out some details. What I am doing is porting code from a Macintosh project. No threading is necessary. The other thing I should mention is that I need to be able to define the dialog after compile time. I have an application that allows the user to design a custom specialized dialog. My application then generates the resources and combines that with the dialog code for the final plugin (Mac version). It seems like it would be too much trouble to write a resource table into the dll. So I was thinking that I could have an external file in my own format, read that and then create the dialog programmatically. Which platform would be best to do that in? If it's .NET is C# required for using .NET? If so then I probably can't go that way as I have to integrate my control/model code from C++.

Re: Newbie: Can I do this?

digwizfox4-Aug-04 8:46

digwizfox

4-Aug-04 8:46

Sounds challenging. I've never needed to design a dialogue at run time. I'm not experienced with managed C++ code or C#.

First of all .Net could be used for many things (you don't need to know C# to use VS .NET). You can use .Net to program an application using all unmanaged C++ code if you'd like. Visual Studio .Net has many options and capabilities that are well beyond what I've ever done.

But when I mentioned earlier that a dialogue can be designed in an MFC extension DLL, the .rc file will exist within the DLL and the .Net wizard will take care of that. So I'm only familiar with the process of creating dialogues in the .dll and allowing the .rc file to exist as part of the dll project. Of course that means that the dialogue exists at compile time which isn't what you want, so I can't help you with that particular detail. Perhaps someone with that kind of experience can chime in with some suggestions.

Shawn

Re: Newbie: Can I do this?

cgriffin4-Aug-04 10:10

cgriffin

4-Aug-04 10:10

Thanks for the help. BTW what is managed/unmanaged C++?

Re: Newbie: Can I do this?

digwizfox4-Aug-04 10:24

digwizfox

4-Aug-04 10:24

Unmanaged C++ is basic C++ where you have to do all of your garbage collection of dynamically allocated resources.

With .Net, there are many new complicated features allowing one to have .Net do garbage collection for the programmer. Managed C++ seems like a new concept to me and I've never used it before. I think Java is the same way where the compiler does all of that for you. In unmanaged C++ code you have to delete all of the objects you use new to allocated. That's part of it, in short, but there could be more complex concepts introduced by Managed C++ code.

If you want to do more, do a google search or search the article database within codeproject.com or codeguru.com and you should be able to find more detailed subject matter on that. I'm more of a basic C++ programmer with a lot of embedded design experience where we had no GUI functionality; but recently made the transition to windows programming so all of these concepts of managed code are totally new to me as well.

Regards,
Shawn

iphelper

Zizilamoroso4-Aug-04 4:24

Zizilamoroso

4-Aug-04 4:24

I'm currently testing the iphelper api.

When I request the iftable, dwInOctets is fine, but dwOutOctets always return 0. The same for all output vars in the table. Input is correct though.

Why is that? out is always 0, but my network monitor tells me different.

<br />
// I left the errorchecking out of the snippet,<br />
// no errors were reported anyway.<br />
<br />
MIB_IFTABLE* g_pIfTable=NULL;<br />
ULONG g_ulIfTableSize=0;<br />
<br />
  ...<br />
<br />
GetIfTable(g_pIfTable,&g_ulIfTableSize,TRUE);<br />
g_pIfTable=new MIB_IFTABLE[g_ulIfTableSize];<br />
GetIfTable(g_pIfTable,&g_ulIfTableSize,TRUE);<br />
<br />
CString str;<br />
for(ULONG index=0;index< g_ulIfTableSize;index++)<br />
{<br />
  str.Format("in=%ld out=%ld",g_pIfTable->table[index].dwInOctets,g_pIfTable->table[index].dwOutOctets);<br />
  AfxMessageBox(str);<br />
}<br />

using: [VISUAL STUDIO 6.0 sp5] [WIN98/2]

Re: iphelper

David Crow4-Aug-04 4:30

David Crow

4-Aug-04 4:30

Zizilamoroso wrote:
...my network monitor tells me different.

Is it using GetIfTable()?

"When I was born I was so surprised that I didn't talk for a year and a half." - Gracie Allen

IStorage like functionality in memory

pankajdaga4-Aug-04 4:14

pankajdaga

4-Aug-04 4:14

Hi everyone,

I have to generate an OLE compound file in memory. Unfortunately, I cannot use IStorage interface as the requirement is that I should not create a file on the disk. The whole thing has to be in memory.

I was wondering if there is an IMemoryStorage like interface available. Basically, I want to be able to create the storage object in memory, create a stream and write bytes to it. I was going through MS documentation and could not find much there. I was wondering if someone who has a bit more experience with this, could guide me a little.

Thanks,

Sincerely,
pankaj

Without struggle, there is no progress

Re: IStorage like functionality in memory

C^hris L^osinger4-Aug-04 5:28

C^hris L^osinger

4-Aug-04 5:28

see ILockBytes

Software | Cleek

Re: IStorage like functionality in memory

pankajdaga4-Aug-04 6:49

pankajdaga

4-Aug-04 6:49

Hi,

Well, came across this gem. CreateStreamOnHGlobal

However, I have another question. After I declare a IStream * object. How can I set the name of this stream object. I need to create a stream with a given name. I think the CreateStreamOnHGlobal will be suffice for me. However, I would have to set the name of the created stream object.

Any help would be greatly appreciated.

Thanks,

Sincerely,

Pankaj

Without struggle, there is no progress

Menus in VC 7 not working after resource cleanup

PrashantJ4-Aug-04 3:53

PrashantJ

4-Aug-04 3:53

Hi,

I did some resource-cleanup in my VC++ application, where in I deleted unused ID's, re-numbered the ID's according to MFC standards. But now my menus do not work. I checked the correspoding ID for the menu, the numerical value all seemed to be OK(unique across projects).

Can anybody help me to figure out what is going wrong?

Thanks,
Prashant

Re: Menus in VC 7 not working after resource cleanup

Tim Smith4-Aug-04 3:59

Tim Smith

4-Aug-04 3:59

Rebuild the whole project/solution. RESOURCE.H is a special file and changes to it does not force all files using it to recompile.

Tim Smith

I'm going to patent thought. I have yet to see any prior art.

Re: Menus in VC 7 not working after resource cleanup

PrashantJ4-Aug-04 4:04

PrashantJ

4-Aug-04 4:04

Tim,

I have several projects of which I clean compiled the project that had the menus. Is'nt that enough?

Should I re-compile the whole solution?

Thanks,
Prashant

Using Created() CListBox

gokings4-Aug-04 3:52

gokings

4-Aug-04 3:52

I have a rather basic MFC question. It is clear to me how to use the Create() method of a CListBox to create one. It is not clear to me what to do with it after it is created. As far as I know, it does not have a DoModal() method as a CDialog object does or something analogous to the TrackPopupMenu() method of a CMenu object.

Does anyone have an example Creating and displaying a CListBox? I want the CListBox to "return" when the user makes a selection, and then to inquire of the CListBox which selection was made.

Thanks

Re: Using Created() CListBox

David Crow4-Aug-04 4:25

David Crow

4-Aug-04 4:25

My first question would be why are you creating it dynamically instead of making it part of the dialog template?

gokings wrote:
It is not clear to me what to do with it after it is created.

Add items to it, or perhaps I don't quite understand your question.

gokings wrote:
As far as I know, it does not have a DoModal() method as a CDialog object does or something analogous to the TrackPopupMenu() method of a CMenu object.

Why are you comparing it to a CDialog or CMenu object? A listbox is a control that is placed on a dialog and enables the user to choose one option from a list of possibilities.

gokings wrote:
Does anyone have an example Creating and displaying a CListBox?

It's such a common control that examples are everywhere. Search here at CP for starters, and then Google for even more.

gokings wrote:
I want the CListBox to "return" when the user makes a selection, and then to inquire of the CListBox which selection was made.

The analogy of "returning" when the user makes a selection makes no sense. When a selection is made from a listbox, the dialog will receive a LBN_SELCHANGE message. If you are using MFC, the dialog will need a ON_LBN_SELCHANGE handler instead. At that point, you can get the text and/or index of the currently selected item.

"When I was born I was so surprised that I didn't talk for a year and a half." - Gracie Allen

Re: Using Created() CListBox

gokings4-Aug-04 5:24

gokings

4-Aug-04 5:24

The crux of the matter is that I want to display a popup menu, but the CMenu class has limitations making it unsuitable for my needs. Someone suggested that I use a Listbox instead of a Menu. From this I assumed that a Listbox could exist independently of a dialog box. Realizing that this is not the case makes everything fall into place.

As for not knowing what to do with a Listbox once it was created, in the context of my question I meant how to cause it to interact with the user. It seems to me that it could be attached at run time to any window, such as a FrameWnd, but perhaps it must be part of a dialog as you indicate.

As far as examples being everywhere, if what you say is true, there are no examples of doing what I wanted to do, as it can't be done. I don't need an example of creating a Listbox on a dialog, a monkey could figure that out without an example.

Yes, I am aware of handling ON_LBN_SELCHANGE, but I was hoping that there was a "modal" alternative.

Regards

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