C / C++ / MFC

Re: LogonUser() Function Issues

1-Aug-06 19:53

It's an out variable, which means you need no pass any values for it. You will get a pointer to a to a token that represents the specified user.

You can pass like

HANDLE hUser = NULL;
LogonUser(....,...,&hUser)

SaRath.

"Where I am from, there is no plan B. So, take advantage of today becuase tomorrow is not promised. - 50 Cent"

My Blog | Understanding State Pattern

Naveen1-Aug-06 19:56

Naveen

1-Aug-06 19:56

The last onr is an out parameter. I.e that varaible returnds some value from the function..

eg..

HANDLE hToken = 0;

LogonUser( ..., &htoken );

nave

Re: LogonUser() Function Issues

Programm3r1-Aug-06 20:03

Programm3r

1-Aug-06 20:03

Thanx guys ....

Smile | :)

Regards

Programm3r

DLL Issue

0xFEDE1-Aug-06 19:21

0xFEDE

1-Aug-06 19:21

Hi, everybody. I'm a little stuck. I have no experience with DLL's and I'm trying to make something with'em.
I'm programming a dll (that calls a windows dll) wich contains the functions I want to use in my app. It compiles fine. But when I build my program that uses my dll, I get the next linking stage error:

MyProgram.obj : error LNK2001: unresolved external symbol "public: unsigned short __thiscall CMyProgramApp::OpenFile(class CString)" (?OpenFile@MyProgramApp@@QAEGVCString@@@Z)

Little help?
Znx.

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Programm3r1-Aug-06 19:29

Programm3r

1-Aug-06 19:29

Hi,

OK, I could be wrong on this one but, in my dll experience, it's because it cant find a certain function. I think it is the function in the dll you wrote. I would say try including the dll into program thats calling the dll you wrote. Hope it works.

Regards

Programm3r

Programm3r1-Aug-06 19:49

Programm3r

1-Aug-06 19:49

OK, my bad .... it's not the dll it's the lib .... close enough

OMG | :OMG:

Regards

Programm3r

Sarath C1-Aug-06 19:31

1-Aug-06 19:31

You application should link with that library. which means, in your Project Properties (Settings) give lib file of the DLL. e.g SampleDLL.lib

SaRath.

"Where I am from, there is no plan B. So, take advantage of today becuase tomorrow is not promised. - 50 Cent"

My Blog | Understanding State Pattern

Remove from Heap using delete.

Naveen1-Aug-06 19:44

Naveen

1-Aug-06 19:44

u have to specify the lib file of that dll.

for that take project settings->Link tab

In the object/Library edit box give the name of the lib file. then try compiling.

nave

HakunaMatada1-Aug-06 19:00

HakunaMatada

1-Aug-06 19:00

I have the following piece of code.

char* strFile = new char[50] ;<br />
CString str( "Hello\nCoders" ) ;<br />
strFile = str.GetBuffer( str.GetLength() );<br />
std::ofstream myfile;<br />
myfile.open ("d:\\example.txt");<br />
myfile << strFile ;<br />
myfile.close() ;<br />
delete[] strFile ;

The program throws a Debug assertion error at delete[] strFile ;. The function throwing the Exception is _CrtIsValidHeapPointer(pUserData).

I was of the impression that creation with new must be followed by cleanup with delete. Seems like I am wrong or I did something wrong in the above code. Can anyone explain?

---

Hakuna-Matada Beer | [beer]

It means no worries for the rest of your days...
It's our problem free, Philosophy
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Sarath C1-Aug-06 19:14

1-Aug-06 19:14

Hakuna-Matada wrote:
char* strFile = new char[50] ;
strFile = str.GetBuffer( str.GetLength() );

when the scope of the variable ends, the destructor of the CString variable will be called. as per the implemantation of CString if you call GeBuffer, you should call ReleaseBuffer before calling any other functoins in CString else it will throw a debug asertion. Here the destructor itself a "silent" function. Hope you clear

SaRath.

"Where I am from, there is no plan B. So, take advantage of today becuase tomorrow is not promised. - 50 Cent"

My Blog | Understanding State Pattern

Naveen1-Aug-06 19:24

Naveen

1-Aug-06 19:24

In addition to what sarath said

char* strFile = new char[50] ;
strFile = str.GetBuffer( str.GetLength() ); causes a memory leak.

char* strFile = 0;
strFile = str.GetBuffer( str.GetLength() );

this is enough. And dont call delete.

nave

Sarath C1-Aug-06 19:35

1-Aug-06 19:35

In addition to Naveen said,
Use GetBuffer only if you are doing some modifications on the CString.
operator LCTSTR (const char*) has been overloaded in CString for reading purpose.

SaRath.

"Where I am from, there is no plan B. So, take advantage of today becuase tomorrow is not promised. - 50 Cent"

My Blog | Understanding State Pattern

Re: Remove from Heap using delete. [modified]

HakunaMatada1-Aug-06 19:43

HakunaMatada

1-Aug-06 19:43

Hi. Thanks for your reply. Well now I have..

char* strFile = new char[50] ;<br />
CString str( "Hello\nCoders" ) ;<br />
strFile = str.GetBuffer( str.GetLength() );<br />
str.ReleaseBuffer() ;<br />
std::ofstream myfile;<br />
myfile.open ("d:\\example.txt");<br />
myfile << strFile ;<br />
myfile.close() ;<br />
delete[] strFile ;

but it still doesn't work. As you may have noticed, I used the ReleaseBuffer as you had suggested but to no avail. Am I doing something wrong?

---

Hakuna-Matada Beer | [beer]

It means no worries for the rest of your days...
It's our problem free, Philosophy
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Sarath C1-Aug-06 20:13

1-Aug-06 20:13

why you are using the same buffy code?
This will work fine...

CString str( "Hello\nCoders" ) ;
std::ofstream myfile;
myfile.open ("d:\\example.txt");
myfile << (LPCTSTR)str;
myfile.close() ;

SaRath.

"Where I am from, there is no plan B. So, take advantage of today becuase tomorrow is not promised. - 50 Cent"

My Blog | Understanding State Pattern

Last modified: Wednesday, August 02, 2006 1:15:50 AM --

HakunaMatada1-Aug-06 21:18

HakunaMatada

1-Aug-06 21:18

Thanks for your time. Now I understand. Smile | :)

---

Hakuna-Matada Beer | [beer]

It means no worries for the rest of your days...
It's our problem free, Philosophy
<marquee behavior="alternate" scrollamount="5" scrolldelay="50"> Jig | [Dance]

Steve Echols1-Aug-06 19:25

Steve Echols

1-Aug-06 19:25

Make sure you call ReleaseBuffer after a GetBuffer or GetBufferSetLength.

This works:

<br />
	CString str( "Hello\nCoders" ) ;<br />
	std::ofstream myfile;<br />
	myfile.open ("c:\\example.txt");<br />
	myfile << str.GetBuffer( str.GetLength() ) ;<br />
	str.ReleaseBuffer();<br />
	myfile.close() ;<br />

- S
50 cups of coffee and you know it's on!

Sarath C1-Aug-06 19:34

1-Aug-06 19:34

Steve Echols wrote:
myfile << str.GetBuffer( str.GetLength() ) ;

In this code, it's not doing any editing. So that we can simply use the string object like this

myfile << (LPCTSTR) str;

SaRath.

"Where I am from, there is no plan B. So, take advantage of today becuase tomorrow is not promised. - 50 Cent"

My Blog | Understanding State Pattern

Steve Echols1-Aug-06 20:13

Steve Echols

1-Aug-06 20:13

You are correct sir. I think I was just trying to stress the ReleaseBuffer call if you call GetBuffer.

- S
50 cups of coffee and you know it's on!

Sarath C1-Aug-06 20:14

1-Aug-06 20:14

SaRath.

"Where I am from, there is no plan B. So, take advantage of today becuase tomorrow is not promised. - 50 Cent"

My Blog | Understanding State Pattern

Amar Sutar1-Aug-06 19:26

Amar Sutar

1-Aug-06 19:26

You are first allocated a buffer on the heap, of size 50. You store the pointer in strFile. Then you do a CString::GetBuffer on a CString object, and overwrite the value in strFile with this new value, thus creating a storage leak.

Also, there is no need for the parameter to GetBuffer.

When you call delete, which frees the CString buffer out
from under the CString, then the CString destructor sees a completely screwed-up heap.

LPTSTR strFile = str.GetBuffer();
std::ofstream myfile;
myfile.open ("d:\\example.txt");
myfile << strFile ;
myfile.close() ;

Amar Smile | :)