windows forms scrollbar problem? - Managed C++/CLI Discussion Boards

Managed Extensions and native code. Bug?

abartosh24-Oct-05 23:16

24-Oct-05 23:16

Hello,

I found really unexpected behaviour of calls from C++ managed extensions, to native code. Following code shows what I wanted to do:

#pragma unmanaged
class UnmanagedClass
{
public:
virtual bool unmanagedFunction() const
{
return false;
}
};

#pragma managed
void managedFunction()
{
UnmanagedClass* object = new UnmanagedClass();
bool result = object->unmanagedFunction();
}

The question is- what would be the value of "result" after
virtual function call? Well.. believe me or not, but it's TRUE!
I debuged it in disassembly window, and inside native code-
the value of EAX (AL actually) register is correctly set to FALSE (xor al, al)
When the function does return, my debuger shows that EAX value has changed- into TRUE! There must be some kind of managed wrapper between Managed Extensions code and native code.

Has anybody any idea what is going on here?
And how to solve the problem?

Re: Managed Extensions and native code. Bug?

IdUnknown26-Oct-05 9:28

IdUnknown

26-Oct-05 9:28

I got the same result you got. Don't know why.

Anyway, normally I use the #pragma managed and unmanaged to control the function compilation only and for the class, I use either __nogc or __gc to tell it if I want the class managed or unmanaged.

I tried the modified code below and it works. hope this help.

__nogc class UnmanagedClass
{
public:
virtual bool unmanagedFunction() const
{
return false;
}
};

#pragma managed
void managedFunction()
{
UnmanagedClass* object = new UnmanagedClass();
bool result = object->unmanagedFunction();
}

Re: Managed Extensions and native code. Bug?

Joel Lucsy27-Oct-05 4:26

Joel Lucsy

27-Oct-05 4:26

I believe its been mentioned somewhere that there is a bug in the compiler, or perhaps the runtime, that gets confused with bool in regards to calling unmanaged code from managed code. I believe one work around is to use BOOL instead of bool. I think what happens is that the size is wrong between the two worlds, 8bit in unmanaged, but 32bit in managed, and the translation doen't account for it. I could be wrong, of course.

--
Joel Lucsy

memory allocation problem :(

wangzhi041724-Oct-05 18:08

wangzhi0417

24-Oct-05 18:08

Initially i allocated a buffer:
void *mem = new char[512];

now i want to use 100 bytes start from mem + 10,
so i wrote like this:

void *addr = static_cast<void*>
( static_cast <size_t> mem + 10 );

error occured! so please help me

my IDE is VS.NET 2003! Confused | :confused:

-- modified at 2:08 Tuesday 25th October, 2005

Re: memory allocation problem :(

Kochise24-Oct-05 21:16

Kochise

24-Oct-05 21:16

void* size is null, better cast it on char* :

void* addr = (void*) ((char*) &mem[10]);

If it doesn't compile, try to move the (char*) casting in another location, such :

void* addr = (void*) &((char*) mem[10]);

Kochise

In Code we trust !

Re: memory allocation problem :(

toxcct24-Oct-05 22:55

toxcct

24-Oct-05 22:55

firstly, provide the error message caugth instead of saying that an error occurs. it will help use more efficiently to understand what's happenning.

secondly, be careful when posting template codes (here, with static_cast<>) because the < > are interpreted as html tag delimiters. use the & l t ; and the & g t ; codes, without spaces or check the Ignore HTML tags in this message (good for code snippets) check box at the bottom of where you type your post.

to finish, i'd suggest you this (as i don't know in what type you static_cast your pointer, i may be wrong) :

you cannot apply the + pointer addition operator on a void* operand because the operator + have to know of how many byte it will move to and void have by definition no size. what happens now if you firslty cast mem into char*, add 10 to it (to move it 10 bytes forward) and type cast it back to void* (like following) ??

void* mem = new char[512];
void* addr = static_cast<void*>(static_cast<char*>(mem)+10);

TOXCCT >>> GEII power
[toxcct][VisualCalc]

Hash string function that keeps compare properties

Kochise24-Oct-05 2:54

Kochise

24-Oct-05 2:54

Is there a hash string function that preserves the capability to compare two strings just by comparing their respective hash values ?

Currently, I have to perform a full Str.Compare("other string") in order to sort them. I had also calculated their hash value, but the sorting (Quick Sort, Bubble Sort, whatever...) fails using the hash value. The hash value is mostly random, especially on long strings.

Comparing the hash values (int) would have been quite faster, I have to perform the quickest sort possible on text files larger than 100 MB ! So please don't come with CString as a solution. It works, but asks hours to do the job. CString is perfect to manipulate UI strings, but bad for heavy duty purposes...

So, to sum up, it there a good hash function that will allow :

"Minus string" < "Plus string"
HASH("Minus string") < HASH("Plus string")

Kochise

In Code we trust !

windows forms scrollbar problem?

9ine24-Oct-05 0:14

9ine

24-Oct-05 0:14

it is the scrollbar that we are able to modify SMALLCHANGE and LARGECHANGE values. Setting them to 1 we are able to scroll thru all VALUES between MIN and MAX. !!But if we modify LARGECHANGE to say 10 we will not be able to scroll thru all VALUES? and the scrollbar it self increases in its size? whats the problem

9ine

Preventing all users from terminating a service using task manager in Windows 2003

e_prabhu24-Oct-05 0:06

e_prabhu

24-Oct-05 0:06

Hi,
I am working in Windows 2003 platform. I have a Windows service that runs in the local SYSTEM account. The service is compatible in Windows NT/Me/2k/XP/2k3.

My problem is that I need to restrict users from terminating this service using Windows Task Manager.

For this I tried to step up the previledge of the service using the AdjustTokenPrivileges API, this way I am able to restrict users from terminating the service only on NT/Me/2k/XP. Whereas in 2003 this Privileges boosting does not help and the user is able to terminate the service.

Help me with any other API that you know or a completely different approach is also acceptable.

Advance thanks to ur suggestions. Smile | :)

Re: Preventing all users from terminating a service using task manager in Windows 2003

Judah Gabriel Himango24-Oct-05 12:28

Judah Gabriel Himango

24-Oct-05 12:28

e_prabhu wrote:
My problem is that I need to restrict users from terminating this service using Windows Task Manager.

Bad idea. If you absolutely must, you could make the service restart upon close. But preventing the user from terminating the service is a huge red flag. For any code that isn't part of the OS, this is really unnecessary.

Maybe if you tell us what you are trying to do, we could help you find an alternative solution.

Tech, life, family, faith: Give me a visit.
I'm currently blogging about: Cops & Robbers
Judah Himango

Re: Preventing all users from terminating a service using task manager in Windows 2003

e_prabhu25-Oct-05 2:10

e_prabhu

25-Oct-05 2:10

Hi Judah Himango,

I am developing a windows service that monitors all the processes that are created in the system.
whenever user creates a new process, the service gets the notification from my virtual device driver. I extract the information of the process being created and if the process is a notepad (for example), I kill it from the service. So that I restrict any user from accessing a specific program.

Hence I dont want the user to terminate my service from the task manager (especially in windows 2003)and proceed with the application that I am restricting. help me with ur suggestion.

Re: Preventing all users from terminating a service using task manager in Windows 2003

Sheng Jiang 蒋晟31-Oct-05 6:10

Sheng Jiang 蒋晟

31-Oct-05 6:10

I think you can use the group policy to limit runable programs

http://blog.joycode.com/jiangsheng
http://blog.csdn.net/jiangsheng
http://bloglines.com/public/jiangsheng

Command what is yours
Conquer what is not
---Kane

C++ networking

Deon Minnie23-Oct-05 20:08

Deon Minnie

23-Oct-05 20:08

I've recently been introduced to the networking side. The first task that I must do is to write a C++ program to capture IP traffic e.g. UDP, TCP, etc.
The second task is to feed this data into an database e.g. SQL or Oracle.
The third task is then to provide reports on this information.

I will be glad if somebody could assist me in this regard.

regards

Deon

How to create Gaussian random number

bulgaa23-Oct-05 18:23

bulgaa

23-Oct-05 18:23

Hello?
I need the Gaussian random number generator.
If you have source code, share to me pls

Thank you so much

Re: How to create Gaussian random number

RichardS24-Oct-05 1:01

RichardS

24-Oct-05 1:01

Hi,

Check out "Numerical Recipes in C", Chapter 7.

regards,
Rich

"Programming today is a race between software engineers striving to build bigger and
better idiot-proof programs, and the Universe trying to produce bigger and better idiots.
So far the Universe is winning." -- Rich Cook

rookie question

Binary011022-Oct-05 16:53

Binary0110

22-Oct-05 16:53

I have this program I have to write for school that accepts two integers. hours and minutes. I then have to output the format in 6:00 format. I'm only allowed integer division and and modulus division. I've tried everything I can think of but my output still looks like this. 6:0 Any tips?

BINARY

-- modified at 23:40 Saturday 22nd October, 2005

Re: rookie question

toxcct23-Oct-05 0:23

toxcct

23-Oct-05 0:23

how do you print it ?

using printf("%2d", minutes); would help...

TOXCCT >>> GEII power
[toxcct][VisualCalc]

Re: rookie question

Christian Graus23-Oct-05 12:55

Christian Graus

23-Oct-05 12:55

That sucks - you have to either use some relatively advanced C++ stuff in iostreams, or use C ( i.e. use printf ).

Christian Graus - Microsoft MVP - C++

Re: rookie question

toxcct24-Oct-05 1:16

toxcct

24-Oct-05 1:16

Christian Graus wrote:
That sucks

it was only a suggestion. i never said to use it and nothing else...

TOXCCT >>> GEII power
[toxcct][VisualCalc]

Accessing external devices(I don't have any idea)

Alex Cutovoi21-Oct-05 6:01

Alex Cutovoi

21-Oct-05 6:01

Hi for all

I started to study how I can access external devices in C++. I've entered in MSDN and I've found a thing called HID Collections. By the description of MSDN, HID Collections are a meaningful group of HID controls and HID usages. HID Controls are a data sources and data sinks associated with a HIDClass device. After this description I don't know if this way is correct to study device access.
Iwould like an orientation about this topic. Someone can put a little bit of light in this topic for me? I'm totally newbie in this.

Thanks a lot

Fastest way to check a file exists

[d3m0n]21-Oct-05 4:32

[d3m0n]

21-Oct-05 4:32

Hi My app stalls at startup because a file in the MRU list is on a network drive that doesn't exist.
The exact filename I am trying to add is "\\blah\start.txt".
I call CRecentFileList::Add from InitInstance. This Add function goes away for about 10secs before returning failure.
So I changed my code so that the Add function is only called if the file actually exists. But every function I tried (PathFileExists, _access, CFile::Open etc etc) always stalls for these 10secs.
There must be some function I can use that will check a file exists, which returns immediately... Confused | :confused:

Any ideas?

Thanks

d3m0n

Re: Fastest way to check a file exists

toxcct21-Oct-05 4:44

toxcct

21-Oct-05 4:44

what's your code please ?

these functions are not so long for me...

TOXCCT >>> GEII power
[toxcct][VisualCalc]

Re: Fastest way to check a file exists

[d3m0n]21-Oct-05 5:00

[d3m0n]

21-Oct-05 5:00

<br />
for (POSITION pos = listFiles.GetHeadPosition(); pos; )<br />
{<br />
	CString strFile = listFiles.GetNext(pos);<br />
	if (_access(strFile, 0) != -1)	//takes 10secs if strFile is "\\blah\start.txt"<br />
		m_pmruFiles->Add(strFile);<br />
}<br />

This problem only occurs if I am connected to the network. If disconnected, it returns failure immediately.

Re: Fastest way to check a file exists

toxcct23-Oct-05 0:22

toxcct

23-Oct-05 0:22

this is not a problem a the function but the network access...

if you open a windows explorer and reach the networks around you, explorer will take several seconds to show you the first infos...

TOXCCT >>> GEII power
[toxcct][VisualCalc]

Re: Fastest way to check a file exists

[d3m0n]23-Oct-05 21:37

[d3m0n]

23-Oct-05 21:37

toxcct wrote:
this is not a problem a the function but the network access...

Yes I have come to the same conclusion. I think it is impossible to solve this problem.

Thanks for your help Smile | :)

Cheers
d3m0n

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