C / C++ / MFC Discussion Boards

moodsey21114-Feb-06 19:27

14-Feb-06 19:27

hello... I'm kinda new in using visual C++ in a relational database. I would just like to ask help if someone has a sample code for connecting updating and closing a database. An ADODC or a DAO will work fine with me. Thanks...

--------------------------------Life is simple, You just complicate things----------------------------

-- modified at 1:44 Wednesday 15th February, 2006

Re: Relational Database

Ashutosh_shashi14-Feb-06 19:33

Ashutosh_shashi

14-Feb-06 19:33

tell the adjectly how u want to connect..
Through ODBC , DAO or .. any other way..
Then i will send u a sample code for that

Ashutosh

Re: Relational Database

moodsey21114-Feb-06 19:43

moodsey211

14-Feb-06 19:43

I'm using ADODC. But you could send me an example for a DAO. I'm choosing from the two. And i'm a little bit confuse...

-----------------------------------Life is simple, You just Complicate Things-----------------------------

Re: Relational Database

Ashutosh_shashi14-Feb-06 22:11

Ashutosh_shashi

14-Feb-06 22:11

Sample Code for DAO-----> Try this--->

CString csQuery; -->à SQL Query
CsaoDatabase pUserDB = new CDaoDatabase();

//Open DataBase in Read Only Mode
m_pUserDB->Open(Path_of_Database,FALSE, TRUE, _T(""));

CDaoRecordset m_pDaoUserRS = new CDaoRecordset(m_pUserDB);
m_pDaoUserRS->Open(AFX_DAO_USE_DEFAULT_TYPE,csQuery,dbReadOnly);

COleVariant varValue;
m_pDaoUserRS->GetFieldValue("Field_Name_of_Database",varValue);

Ashutosh

Re: Relational Database

David Crow15-Feb-06 4:12

David Crow

15-Feb-06 4:12

moodsey211 wrote:
An ADODC...

Isn't that a VB thing?

Anyway, see here.

"The greatest good you can do for another is not just to share your riches but to reveal to him his own." - Benjamin Disraeli

memory leak!!!!!!

naguu14-Feb-06 18:39

naguu

14-Feb-06 18:39

In my code i have a situation like..

char * getmestring()
{
char *str = new char[20];
str = "myname";
return str; --> str not at all release..
}
int main()
{
char name = getmestring();
cout<<name<<endl;
if(name="" !="NULL)"
="" {
="" delete="" []="" name;="" --=""> this is causing the debug assertion failed..
}
}
can u give me some idea to remove leaks in that piece of code..

nagesh

-- modified at 0:40 Wednesday 15th February, 2006

Re: memory leak!!!!!!

namaskaaram14-Feb-06 18:42

namaskaaram

14-Feb-06 18:42

char *name = getmestring();

cheerz!

dont want,dont want thinking,climbing on head and jumping grass!
(venda venda ennu vicharikumbol thellayill keyaree chadunnoda pulle!)

Re: memory leak!!!!!!

Stephen Hewitt14-Feb-06 18:55

Stephen Hewitt

14-Feb-06 18:55

naguu wrote:
char * getmestring()
{
char *str = new char[20];
str = "myname";
return str; --> str not at all release..
}

The memory you allocate with the new statement isn't being used at all. The "str = "myname";" line doesn't copy the string; it copies over the address of the memory you allocated with new with the address of the string literal "myname".

This is probably what you mean:

char * getmestring()
{
  char *str = new char[20];
  strcpy(str, "myname");
  return str; --> str not at all release..
}

Steve

Re: memory leak!!!!!!

Ashutosh_shashi14-Feb-06 19:20

Ashutosh_shashi

14-Feb-06 19:20

Try this ................
int main()
{
char *name = getmestring(); --> modify this line
cout<<name<<endl;
if(name !="NULL)
{
" name="NULL;" ---=""> Add this line
delete [] name; --> this is causing the debug assertion failed..
}
}

Inform me if success...

Ashutosh

Re: memory leak!!!!!!

namaskaaram14-Feb-06 19:42

namaskaaram

14-Feb-06 19:42

int main()
{
char *name = getmestring(); --> modify this line
cout<<name<<endl;
if(name != NULL)
{
name = NULL; ---> Add this line
delete [] name; --> this is causing the debug assertion failed..
}
}

~~assigning name =NULL and then deleting it will give u an error since u r trying to delete a block that points to the null address!!!!~~rather the code should be more like.....

int main()
{
char *name = NULL;  
name = getmestring(); 
cout<<name<<endl;

if(name != NULL)
delete [] name;

}

cheerz!

dont want,dont want thinking,climbing on head and jumping grass!
(venda venda ennu vicharikumbol thellayill keyaree chadunnoda pulle!)

-- modified at 3:35 Wednesday 15th February, 2006

Re: memory leak!!!!!!

Ryan Binns14-Feb-06 19:51

Ryan Binns

14-Feb-06 19:51

namaskaaram wrote:
assigning name =NULL and then deleting it will give u an error since u r trying to delete a block that points to the null address!!!!

No it won't. It won't do as intending, but deleteing a NULL pointer is a perfectly valid operation - it does not cause errors.

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"

Re: memory leak!!!!!!

BadKarma14-Feb-06 20:29

BadKarma

14-Feb-06 20:29

But then again there will be a memory leak

codito ergo sum

Re: memory leak!!!!!!

Ryan Binns14-Feb-06 21:27

Ryan Binns

14-Feb-06 21:27

Usually, but that's not the point I was making. His statement was that deleteing a NULL pointer causes an error because the pointer is NULL. This is not correct.

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"

Re: memory leak!!!!!!

BadKarma14-Feb-06 21:43

BadKarma

14-Feb-06 21:43

I know,

I was just trying to point out for naguu that altough setting a pointer to NULL and then deleting wont cause an error it will cause a memory leak. Which was (one of) his first problems.

To conclude:

char * getmestring()
{
char *str = new char[20];

// FROM <a href = "http://www.codeproject.com/script/comments/forums.asp?msg=1371347&forumid=1647#xx1371359xx" rel="nofollow">Stephen Hewitt</a>[<a href = "http://www.codeproject.com/script/comments/forums.asp?msg=1371347&forumid=1647#xx1371359xx" target = "_blank" rel="nofollow">^</a>]
// str = "myname";
strcpy(str, "myname"); 
return str;
}
int main()
{

// FROM <a href = "http://www.codeproject.com/script/comments/forums.asp?msg=1371347&forumid=1647#xx1371347xx" rel="nofollow">namaskaaram</a>[<a href = "http://www.codeproject.com/script/comments/forums.asp?msg=1371347&forumid=1647#xx1371347xx" target = "_blank" rel="nofollow">^</a>]
//char name = getmestring();
char *name = getmestring(); 
cout<<name<<endl;
if(name != NULL)
{
delete [] name; 
}
}

codito ergo sum

Re: memory leak!!!!!!

Ryan Binns14-Feb-06 21:48

Ryan Binns

14-Feb-06 21:48

Fair enough Smile | :)

BadKarma wrote:
//char name = getmestring();char *name = getmestring();

I assumed here he just typed into the message wrong - otherwise his code wouldn't have even compiled, much less got memory leaks Wink | ;)

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"

Re: memory leak!!!!!!

namaskaaram14-Feb-06 21:34

namaskaaram

14-Feb-06 21:34

.....yeah just tried it out!....ur right! thankz! Smile | :)

hmm,doesnt the location pointed by the pointer gets lost when made null?,so i believe we loose the dynamically created objects location dont we?so there is a mem leak right?;)
anywayz thanx for the correction! Smile | :)

cheerz!

dont want,dont want thinking,climbing on head and jumping grass!
(venda venda ennu vicharikumbol thellayill keyaree chadunnoda pulle!)

Re: memory leak!!!!!!

Ryan Binns14-Feb-06 21:44

Ryan Binns

14-Feb-06 21:44

There is usually a memory leak when you delete NULL. Not always, however. if you have a class that allocates memory using new, it's reasonably standard practice to delete it in the destructor. If you have another cleanup routine that deletes the pointer (and then sets it to NULL - always an excellent idea), then the delete in the destructor doesn't need to have a if (!NULL) check around it - it makes no difference whether the pointer is NULL or not.

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"

Re: memory leak!!!!!!

Ashutosh_shashi14-Feb-06 21:18

Ashutosh_shashi

14-Feb-06 21:18

namaskaaram wrote:
assigning name =NULL and then deleting it will give u an error since u r trying to delete a block that points to the null address!!!!
rather the code should be more like.....

Do you know basic of pointers.........?

Ashutosh

Re: memory leak!!!!!!

ThatsAlok14-Feb-06 23:11

ThatsAlok

14-Feb-06 23:11

namaskaaram wrote:
int main(){char *name = NULL; name = getmestring(); cout<<name<<endl;if(name !="NULL)delete" []="" name;}<="" blockquote="">

change it to

if(name != NULL)
delete [] name;
name=NULL

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

cheers,
Alok Gupta
VC Forum Q&A :- I/ IV

Re: memory leak!!!!!!

David Crow15-Feb-06 4:15

David Crow

15-Feb-06 4:15

Since you are using C++, why mess with char at all? Use std::string instead and you won't have these silly memory issues.

"The greatest good you can do for another is not just to share your riches but to reveal to him his own." - Benjamin Disraeli

Encryption

Tony Kurishunkal14-Feb-06 17:41

Tony Kurishunkal

14-Feb-06 17:41

Hello! I'm a c++ beginner, and i'm trying to encrypt a simple text file, but, as I search in the internet, there are a lot of algorithms that I could use... so I'm a little bit confused... Can you tell me wich one is the best for me?
The file can be encrypted / decrypted with a Key or passhrase. Maybe using a symmetric algorithm ?
Well, I hope you could help on this..... Thanks a lot!

Aby Skaria

Re: Encryption

namaskaaram14-Feb-06 18:46

namaskaaram

14-Feb-06 18:46

Jean-loup Gailly algo!.....u can get their free lib!.... Wink | ;-)

click this[^]

dont want,dont want thinking,climbing on head and jumping grass!
(venda venda ennu vicharikumbol thellayill keyaree chadunnoda pulle!)

Re: Encryption

moodsey21114-Feb-06 19:22

moodsey211

14-Feb-06 19:22

hello..! Well most often in encryption the longer the key the better. So that brute force will not be applied on your encryption algorithm. You should consider security threats before deciding which one to use.

-------------------Life is simple, You just complicate things --------------

Application crashed on client side not on my side

zahid_ash14-Feb-06 17:34

zahid_ash

14-Feb-06 17:34

Hi,

I have build the application using MFC, VC++ 6 on Windows XP. It is runnign fine in on my system. But it get crashed on the cleint side (operating system Win2K) but sometimes it worked fine .cleint is too far from me, I cannot debugg it personaly over there.

How can I check it that at which pont it is crashing.

Thanks

Regards.

Re: Application crashed on client side not on my side

Ashutosh_shashi14-Feb-06 19:30

Ashutosh_shashi

14-Feb-06 19:30

First check for any memory leak in your project-- u can use CMemoryState class for that
If it is ok the check for resource leak.
if it is ok the ckeck all the syncronization objects u r using , is there is any chance of deadlock , it may be possible if u r using timer function fo syncronization object
for locking and unlocking.
CHeck it out ...
I will try for other than these reasons for this

Ashutosh

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