C / C++ / MFC

Re: Can we use registry for..

19-Jun-09 3:09

ramana.g wrote:
Is it ok if we write thousands of key-value entries into registry? How it will effect the performance of the system? Please suggest me..

Probably not a good idea. Why not put them in a file, maybe (something like) a SQLite database or an XML file?

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C^hris L^osinger19-Jun-09 3:40

C^hris L^osinger

19-Jun-09 3:40

Registry size is limited (to 25% of the paged pool). this can be changed by the user, though it's not obvious to most people how to do it. so, it's probably much better if you just write your data to a file.

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Re: Can we use registry for..

Vaclav_19-Jun-09 14:11

Vaclav_

19-Jun-09 14:11

I think it depends on how often does an ordinary user access registry.
When it is used only during the application initialization it is relatively fast. Of course it has hardware constrains, but again, to the average user (word processing, e-mail etc.) with GB’s of RAM it should make little difference. My “ancient “ PC with circa 380 MB of RAM and 1 GHz processor struggles when I do key searches.
I know this is not what you are asking. I guess to get a real answer you need to write a test program to really find out how registry interact with running application.
Good luck.
Cheers Vaclav

How to write to the part of memory with no Writeable permission

trungkiendt819-Jun-09 2:21

trungkiendt8

19-Jun-09 2:21

I have a program that write to other process's memory, but some part of that memory is NOT writeable. Can anyone tell me how to write to that part of memory, without changing the actual physical file?

Thanks and regard !

Re: How to write to the part of memory with no Writeable permission

molesworth19-Jun-09 2:36

molesworth

19-Jun-09 2:36

How exactly are you writing to the other process' memory, and why? How are you accessing the memory? how are you getting its address?

If you need to write to some memory area, e.g. a buffer, then it shouldn't be protected, so you shouldn't have problems.

If you're trying to write to protected memory, well, in general, you can't.

There are three kinds of people in the world - those who can count and those who can't...

Re: How to write to the part of memory with no Writeable permission

trungkiendt819-Jun-09 3:03

trungkiendt8

19-Jun-09 3:03

Actually, this is what i'm doing:

First, I use CreateProcess(...) to execute an application.
Then WriteProcessMemory(...) to write to that process's memory.

But in fact, some part of that process's memory space is NOT writeable. So what I want is a mechanism to write to protected memory.

Re: How to write to the part of memory with no Writeable permission

Cedric Moonen19-Jun-09 3:05

Cedric Moonen

19-Jun-09 3:05

What are you trying to do in fact ? Ok, please don't answer something like "I want to write the memory of a process"... I would like to know the higher level reason why you are trying to do something like that (specially when you want to write somewhere you don't have access to).

Cédric Moonen
Software developer

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Re: How to write to the part of memory with no Writeable permission

trungkiendt819-Jun-09 3:19

trungkiendt8

19-Jun-09 3:19

It's not a project in fact Smile | :)

I just wonder why a debugger can access and change any memory location of any (may be not some critical ) process that it's debugging.
Then I study and find out the way to access other process's mem, but hooked up with some location that CAN'T be write (with my mechanism of course Smile | :)

).
But a debugger still can write to that location. So there must be a solution or an other mechanism to do that?

Re: How to write to the part of memory with no Writeable permission

molesworth19-Jun-09 4:36

molesworth

19-Jun-09 4:36

A debugger is effectively the same process as the program it's debugging (OK, this is a very big generalisation) so it can access the memory without any problems. However, in a debugger, e.g. Visual Studio, you'll find that you still get errors if you try to access protected memory, like memory in a completely different process.

Debuggers aren't doing anything special, it's just the way they interact with the program being debugged that makes it look like they are. Smile | :)

edit : Actually, I think a lot of these kinds of questions come down to low-level stuff like assembler and computer architecture not being taught any more. Knowing what goes on under the hood can help you understand things a lot better, and often help you write better code. I've even had someone (a graduate, believe it or not) ask me "When you call a function, how does it know where to return back to?". OMG | :OMG:

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Re: How to write to the part of memory with no Writeable permission

Stuart Dootson19-Jun-09 3:08

Re: How to write to the part of memory with no Writeable permission

19-Jun-09 3:08

You might be able to with some kernel level driver? However, if some part of the virtual memory space has been marked as read-only, that's controlled by the memory management unit of the processor, so good luck with changing that....

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

norish19-Jun-09 6:04

norish

19-Jun-09 6:04

We usually dont need to access such privileged area if we do not intend to create some virus or malware thing.

But some hint in the suitable situations; Generally, higher privileged process (like memory manager of os) can change the permission of the memory attributes.
And another solution can be done like an os loader. Some debugger dose it so, I think.
Good luck hacker. Poke tongue | ;-P

project setting

transoft19-Jun-09 2:17

transoft

19-Jun-09 2:17

Hi
There are some setting in the project property like:

$(IntDir)\
$(TargetPath)
$(OutDir)\$(ProjectName).exe

Where are they defined? How can I change and add some more?

Best regards,

Re: project setting

David Crow19-Jun-09 2:48

David Crow

19-Jun-09 2:48

transoft wrote:
Where are they defined?

See here.

transoft wrote:
How can I change and add some more?

For VS6, open Project Settings (Alt+F7). Click the Custom Build tab. Click the Directory and Files buttons.

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Re: project setting

Stuart Dootson19-Jun-09 3:05

19-Jun-09 3:05

$(IntDir) and $(OutDir) are defined in the General section of your project's properties by the 'Intermediate Directory' and 'Output Directory' properties respectively.

$(TargetPath) is the 'Output File' property in the Linker->General section of the project properties.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Preprocessor question

rrrado19-Jun-09 2:08

rrrado

19-Jun-09 2:08

How can I use string constant as parameter to function requiring wchar_t* ?

#define MYSTR "abc"
// #define MYSTRW L"abc"   // I don't like this solution because I have to update the same 2 strings

wstring x(MYSTR); // error C2664

thank you

Stuart Dootson19-Jun-09 2:26

19-Jun-09 2:26

This MAKELONG macro definition will work for you.

#include <string>

#define MYSTR "abc"
#define MAKELONG2(S) L##S
#define MAKELONG(S) MAKELONG2(S)

std::wstring a(MAKELONG(MYSTR));

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

rrrado19-Jun-09 2:45

rrrado

19-Jun-09 2:45

great, thank you Big Grin | :-D

I was trying just 1st macro before and I was getting the macro's name in my string Laugh | :laugh:

Stuart Dootson19-Jun-09 3:36

19-Jun-09 3:36

Yup - been there, done that Smile | :)

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

XMLHTTP createinstance exception

CPallini19-Jun-09 2:26

CPallini

19-Jun-09 2:26

use

#define MYSTR  _T("abc")

and then accordingly define (or not) the UNICODE symbol.
Smile | :)

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Ash_VCPP19-Jun-09 2:00

Ash_VCPP

19-Jun-09 2:00

Hi All,

i am using xmlhttp request method to get some xml data from server but i am not even able to create instance of xmlhttp object.

hr=pIXMLHTTPRequest.CreateInstance("Msxml4.XMLHTTP.4.0");

above hr is returning false. Please give some solution.

Thanks A Ton
Ash_VCPP
walking over water is just knowing where the stones are.....

CPallini19-Jun-09 2:13

CPallini

19-Jun-09 2:13

It does NOT return false. It may return a failure code, usually useful to understand what happend.
Smile | :)

Ash_VCPP19-Jun-09 2:38

Ash_VCPP

19-Jun-09 2:38

yes exactly it returned some code...but hoe do i know its meaning....or can you please tell me the possible reasons of its failure

Thanks A Ton
Ash_VCPP
walking over water is just knowing where the stones are.....

CPallini19-Jun-09 3:10

CPallini

19-Jun-09 3:10

Ash_VCPP wrote:
but hoe do i know its meaning....

See, for instance [^]. You may also try to post it here.
Smile | :)