C / C++ / MFC

Mark Salsbery10-Sep-08 15:55

10-Sep-08 15:55

How can a pointer accidentally be deleted?

Mark

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

uusheikh10-Sep-08 16:00

10-Sep-08 16:00

I didnt mean 'accidentally deleted' in that way, what i meant was that, if i pass a pointer to a function, i dont want the function to take 'ownership' and delete it etc (due to bad programming on the function side, which i have no control of it). If I allocated the pointer, only i will have the ability to delete it. Other consuming functions can only process, read/write and not delete.

Can it be done?

Mark Salsbery10-Sep-08 16:04

10-Sep-08 16:04

uus831 wrote:
Can it be done?

Not without control of the consuming function.

The caller wouldn't even know if the pointer
was deleted by the consumer.

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

uusheikh10-Sep-08 16:09

10-Sep-08 16:09

I'm looking at smart pointers, auto pointers. Can it be used?

Bram van Kampen10-Sep-08 17:29

Bram van Kampen

10-Sep-08 17:29

Short Answer: NO.

Longer Answer:
You seem to be used to VB. Welcome to 'C' One of the Advantages of 'C' and 'CPP' over the likes of Basic is, that you have access at your own discression to your own dicression to all actual bytes in memory. That means, Greater Access, but also No Secret Actions which change the world around you when you're not looking. This great power comes with the great responsibility of having to put into place your own system of checks and balances to ensure that you don't use a pointer after you delete it's contents. The Standard way of dealing with this is a programming discipline of setting a pointer to NULL when de-allocated, and of duplicating a pointer only under reserve.

This is a very big subject in terms of language definition, but quite simple if you get a picture in mind about how code is laid out.

Regards Smile | :)

Bram van Kampen

uusheikh10-Sep-08 18:32

10-Sep-08 18:32

Thanks.. I get the picture now. There is simply no way.. Have to trust the programmer Smile | :)

Mark Salsbery11-Sep-08 4:23

Passing CString between DLLs

11-Sep-08 4:23

uus831 wrote:
Have to trust the programmer

Yeah. The best you can do is have a well defined,
consistent, and documented interface.

It's still up to us programmers to follow the rules,
no different than using something like the Win32 APIs.

Mark

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

uusheikh10-Sep-08 15:42

10-Sep-08 15:42

I have a DLL created in Visual Studio 2005, and going to use it in Visual Studio 2008. The function in the DLL takes CString as a parameter. Is it safe to send CString from VS08 to VS05/VC6 DLL? I think different versions of VC++ will have different internal implementation of CString and it would not be safe. Whats the best way?

Mark Salsbery10-Sep-08 16:01

10-Sep-08 16:01

The VS2005 and VS2008 sides are going to use different
CRT libraries so passing anything but const pointers
isn't going to be safe.

Also, as you mentioned, the CString implementations may be
different so passing CStrings isn't safe.

Passing LPCSTRs is safest - let the receiver make a local
CString copy from the passed pointer if necessary.

Mark

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

uusheikh10-Sep-08 16:06

10-Sep-08 16:06

What about sending std::string? Is it also NOT safe?

Bram van Kampen10-Sep-08 17:33

Bram van Kampen

10-Sep-08 17:33

What about sending it as a LPCSTR
Smile | :)

Bram van Kampen

uusheikh10-Sep-08 18:33

10-Sep-08 18:33

Maybe I should..

Mark Salsbery11-Sep-08 4:20

memory mismatch usage between duplicate instances?

11-Sep-08 4:20

uus831 wrote:
What about sending std::string?

Same as CStringT Smile | :)

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

fredsparkle10-Sep-08 14:14

fredsparkle

10-Sep-08 14:14

Got a weird one for everyone.

We have ported our MFC MDI application to VS 2005 and it is is out in beta test with some managed extensions in DLL's.

Most everyone is happy during the beta though we have a handful of users at one company reporting our new snappy product is an obsolete dog, six seconds to display a MFC drop down menu, etc.

XP 3.2GHZ hyper-threaded systems with 2GB of memory and multiple monitors 3-4

Only our application is being reported as slow, others are working fine.

We had them turn off the virtual memory page file and our application started running fine until they loaded a bunch of other applications and left ours quiescent for about 20 minutes. On re-accessing our application it would be initially slow and then pick back up its normal speed.

At this point in looking in the task manager one instance of our application would show as using 50mb of memory and the other would show using 6-8mb of memory and climb back as the user performed operations.

No other site has showed this memory imbalance between instances.

It’s like every time they need our application we are not in memory and have to be reloaded from disk. No where else have we seen this type of imbalance between instances or that we have been pushed out of memory so extremely.

Any idea's what can be causing this?

Re: memory mismatch usage between duplicate instances?

Bram van Kampen10-Sep-08 17:41

Bram van Kampen

10-Sep-08 17:41

What did you send for Beta? Debug or Release.
Did you include (Secret)ErrorReporting Structures with your Beta Version, What did they say,
Can you switch them on again.
What made you decide that the Beta Test was finished, and to go for release.

Regards, Cry | :((

Bram van Kampen

VC++ 6 with Excel Sheets

kasi1410-Sep-08 7:19

kasi14

10-Sep-08 7:19

Hi Everyone,

I am working on a VC++ 6.0 project which require me to write to an existing excel file.
I tried to search, but am not able to find out any sample code.

Can any one guide me on this?

Please direct me to some sample code.

Regards,
krish

David Crow10-Sep-08 7:57

David Crow

10-Sep-08 7:57

You can either use the Excel ODBC driver, or Excel Automation. I've provided an example of the latter a few times in this forum.

"Love people and use things, not love things and use people." - Unknown

"The brick walls are there for a reason...to stop the people who don't want it badly enough." - Randy Pausch

kasi1410-Sep-08 8:49

kasi14

10-Sep-08 8:49

Hi

Thanks for the quick responce.
Can you point me to some sample code?

Regards,
Krish

David Crow10-Sep-08 9:07

David Crow

10-Sep-08 9:07

krish99 wrote:
Can you point me to some sample code?

Search this forum for excel.application going back to 1-Jan-2007.

"Love people and use things, not love things and use people." - Unknown

"The brick walls are there for a reason...to stop the people who don't want it badly enough." - Randy Pausch

Jijo.Raj10-Sep-08 7:58

Jijo.Raj

10-Sep-08 7:58

Please check this knowledge base article - How to automate Excel using Visual C++[^]. It contains necessary code snippet about how to fill and get data.

Regards,
Jijo.

_____________________________________________________

http://weseetips.com[^] Visual C++ tips and tricks. Updated daily.

how to get the subkey value using c++

kasi1410-Sep-08 8:47

kasi14

10-Sep-08 8:47

Thanks for the sample.

Can i use Microsoft Excel 11.0 Object Library/ Microsoft Excel 10.0 Object Library with C++/VC++6
with out .Net Environment?

If i can use, where can i download Microsoft Excel 11.0 Object Library?

Regards,
Ramchandraraju KK

adhilingam10-Sep-08 5:20

adhilingam

10-Sep-08 5:20

Hi In our application the subkey will be dynamically changed, so we can't give subkey name directly. so based on the subkey name, the corresponding subkey value should be retrived. if possible please provide me a sample program to get the subkey values.

Re: how to get the subkey value using c++

Mark Salsbery10-Sep-08 6:27