Re: Declaring too many local variable in a function would affect the performance? - C / C++ / MFC Discussion Boards

Re: Access Voilation ...

Cedric Moonen24-Jul-07 2:37

Cedric Moonen

24-Jul-07 2:37

Where does it crashes exactly in this piece of code ? Did you put breakpoints and check if the variables are correct ?

Cédric Moonen
Software developer

Charting control [v1.2]

Re: Access Voilation ...

Programm3r24-Jul-07 2:42

Programm3r

24-Jul-07 2:42

Variables are correct, because I call the exacpt same function (database class ODBC) a few lines back, without a problem. Please note that this only occurs in the IDE run-time debugging senario. When I compile a .exe and run it, there is no problem with it.

The only programmers that are better that C programmers are those who code in 1's and 0's Green Alien | [Alien]

Programm3r
My Blog: ^_^

Re: Access Voilation ...

David Crow24-Jul-07 3:15

David Crow

24-Jul-07 3:15

Programm3r wrote:
...there is no problem with it...

...that you know of. Problems don't just go away. They can move or be masked, however.

"A good athlete is the result of a good and worthy opponent." - David Crow

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Re: Access Voilation ...

Programm3r24-Jul-07 2:40

Programm3r

24-Jul-07 2:40

Sorry .. after putting in a try and catch block I received the following:

Stack:

:004B453D CODBCDatabase::DriverConnect(this=:0012E38C, szConnStr=:0055F294, szConnStrOut=NULL, hWnd=NULL, drvConn=0 /* sqlNoPrompt */)
:0040EFD0 getDUCNames()
:60601457 OraClient9.OCIServerAttach + 0x67
:08b0698b OCI.OCIServerAttach + 0x2b
:08aa6f69 ; C:\EC-Apps\OracleClient92\BIN\SQORA32.DLL
:08aa6e09 ; C:\EC-Apps\OracleClient92\BIN\SQORA32.DLL
:08aa97f6 ; C:\EC-Apps\OracleClient92\BIN\SQORA32.DLL
:08aa8c67 ; C:\EC-Apps\OracleClient92\BIN\SQORA32.DLL
:08a942ea ; C:\EC-Apps\OracleClient92\BIN\SQORA32.DLL
:74323079 ; C:\WINDOWS\system32\ODBC32.DLL
:74322fbc ; C:\WINDOWS\system32\ODBC32.DLL
:743528f9 ; C:\WINDOWS\system32\ODBC32.DLL

Occurs here at this call:

 // getDUCNames Function
 if (!pdb.DriverConnect(lpSapDsnStr))
	return;
 // CODBCDatabase::DriverConnect function
	ret = SQLDriverConnect(m_hDbc,
....

Does this give a more descriptive explanation ??

The only programmers that are better that C programmers are those who code in 1's and 0's Green Alien | [Alien]

Programm3r
My Blog: ^_^

Re: Access Voilation ...

Cedric Moonen24-Jul-07 2:52

Cedric Moonen

24-Jul-07 2:52

You should check the documentation. It is probably normal that the function throw an exception if something goes wrong. If a function might throws an exception, you should always catch it.

If the problem doesn't occur in your exe, you should check the different pathes that you are using. Some of them might be wrong.

Cédric Moonen
Software developer

Charting control [v1.2]

Re: Access Voilation ...

Programm3r24-Jul-07 3:15

Programm3r

24-Jul-07 3:15

Thanks for the information Cedric, I'll see what I can do. Smile | :)

The only programmers that are better that C programmers are those who code in 1's and 0's Green Alien | [Alien]

Programm3r
My Blog: ^_^

Declaring too many local variable in a function would affect the performance?

Mushtaque Nizamani24-Jul-07 1:45

Mushtaque Nizamani

24-Jul-07 1:45

Hi,
If i declare too many local variables(DWORD, CString, other data type) in a function, would that make my program slow.

Best Regards,
Mushq

Mushtaque Ahmed Nizamani
Software Engineer
Ultimus Pakistan

"English is my second language; please excuse any grammatical or spelling mistakes"

Re: Declaring too many local variable in a function would affect the performance?

Anthony_Yio24-Jul-07 1:51

Anthony_Yio

24-Jul-07 1:51

Depends on what is it doing in the constructor codes of the data type.

Primitive data type should be harmless or at least not noticeable.

If you running out of memory, it would also slow down your program because of resort to virtual memory. (It will slow or crash even for whatever you do I think anyway)

Sonork 100.41263:Anthony_Yio

Re: Declaring too many local variable in a function would affect the performance?

James R. Twine24-Jul-07 2:04

James R. Twine

24-Jul-07 2:04

   Depends on the variable and how it is being used.

   For example, creating a DWORD and adding to it in a loop is has significantly different performance implications than adding to a CString in the same loop.

   I believe it boils down more to not how many variables you have, but how you are using them. Variables that manage resources for you (like CString) are easy to use incorrectly (or at least inefficiently).

   Peace!

-=- James
Please rate this message - let me know if I helped or not!<HR>If you think it costs a lot to do it right, just wait until you find out how much it costs to do it wrong!
Avoid driving a vehicle taller than you and remember that Professional Driver on Closed Course does not mean your Dumb Ass on a Public Road!
See DeleteFXPFiles

Re: Declaring too many local variable in a function would affect the performance?

jhwurmbach24-Jul-07 2:18

jhwurmbach

24-Jul-07 2:18

This Question is a typical case of "premature optimisation".

Code your program.
If its too slow determine why. A profiler would be helpful here.
Fix *that* issue.

Failure is not an option - it's built right in.

Re: Declaring too many local variable in a function would affect the performance?

David Crow24-Jul-07 3:16

David Crow

24-Jul-07 3:16

Technically, yes. Would you notice it? Probably not.

"A good athlete is the result of a good and worthy opponent." - David Crow

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

How to insert a string into the Listbox?

estherpappa24-Jul-07 1:06

estherpappa

24-Jul-07 1:06

Hi to all,
if i type the item in the edit box mean it must add into the listbox.
plz gve me ideas.

Re: How to insert a string into the Listbox?

_AnsHUMAN_ 24-Jul-07 1:14

_AnsHUMAN_

24-Jul-07 1:14

estherpappa wrote:
if i type the item in the edit box mean it must add into the listbox.

Do you mean to say that as you are typing the text in the edit box, the changes should be reflected in the list box too?

Or you mean - that once you have finished typing the text in the edit box and do some action, then only the string should be added to the list box.
If you want this then you should have a look at CListBox::SetItemText()

Somethings seem HARD to do, until we know how to do them.
Wink | ;-)

_AnShUmAn_

Re: How to insert a string into the Listbox?

ShilpiP24-Jul-07 2:27

ShilpiP

24-Jul-07 2:27

http://functionx.com/visualc/controls/listcontrol.htm[^]

Yes U Can ...If U Can ,Dream it , U can do it ...ICAN

Re: How to insert a string into the Listbox?

David Crow24-Jul-07 3:19

David Crow

24-Jul-07 3:19

If you are using MFC:

CString strText;
m_edit.GetWindowText(strText);
m_listbox.AddString(strText);

If not, a Win32 example can also be provided.

"A good athlete is the result of a good and worthy opponent." - David Crow

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Re: How to insert a string into the Listbox?

Hamid_RT31-Jul-07 20:17

Hamid_RT

31-Jul-07 20:17

Or InsertString.

WhiteSky

key codes for alphabets

prithaa24-Jul-07 0:56

prithaa

24-Jul-07 0:56

Hello,

I want to use OnKeyDown() for alphabets Caps and small. But what are the codes to use since for Up and Down arrows I have used VK_DOWN and VK_UP.

I have tried VK_A to VK_Z.But that doesn't work.

Thanks

Re: key codes for alphabets

_AnsHUMAN_ 24-Jul-07 1:25

_AnsHUMAN_

24-Jul-07 1:25

void COnlyForU::OnKeyDown(UINT nChar, UINT nRepCnt, UINT nFlags)
{
if(nChar == 'a' || nChar == 'A')
     // Some code
else if(nChar =='b' || nChar == 'B')
     // We do something else
CDialog::OnKeyDown(nChar, nRepCnt, nFlags);
}

Somethings seem HARD to do, until we know how to do them.
Wink | ;-)

_AnShUmAn_

About Threading model

siddharthsan24-Jul-07 0:55

siddharthsan

24-Jul-07 0:55

Hi,

I am using Windows CE platform for my flashlite plugin application development.In the registry file(.rgs),threading model is set to Both to support both the STA and MTA.
Because of the threading model, I am getting fatal error as ,

"Single-threaded COM objects are not properly supported on Windows CE platform, such as the Windows Mobile platforms that do not include full DCOM support. Define _CE_ALLOW_SINGLE_THREADED_OBJECTS_IN_MTA to force ATL to support creating single-thread COM object's and allow use of it's single-threaded COM object implementations. The thr Cry | :((

eading model in your rgs file was set to 'Free' as that is the only threading model supported in non DCOM Windows CE platforms."

So, I changed the apartment type is changed to free,apartment etc.
like ThreadingModel = Both
ThreadingModel = Free
ThreadingModel = Apartment

But I am getting the same error.It is related to _WIN32_WCE macro?

Please help me to solve this error...

Siddharth

Re: About Threading model

DevMentor.org24-Jul-07 12:54

DevMentor.org

24-Jul-07 12:54

Are you sure you're not doing something wrong?

I am sure single-threaded COM is supported in WinCE as this is very easy to do. COM does this by using a hidden window and a message loop to serialize the calls aka com marshalling.

Do you have the source code for the COM object, can you build it for WinCE and then try to register the com object. Possibly the existing COM object was never built to run on WinCE as some one the APIs on WinCE are light-weight and don't transfer easily from Win32 platforms.. this is what I've read as I have never developed for a WinCE platform.

You can't simpley change a COM object that was STA to MTA free threading model because then your object is not thread safe and will have all kinds of data corruption bugs! You also need to build a thread safe COM object besides the registry setting.

Also STA and MTA support has nothing to do with DCOM!

Yours Truly, The One and Only!

Re: About Threading model

Matthew Faithfull25-Jul-07 1:09

Matthew Faithfull

25-Jul-07 1:09

Seems a bit odd. I use COM on CE all the time and have never seen this problem but I suppose that's because all our stuff is multithreaded. If you have control over your CE platform it's possibly worth experimenting with putting DCOM back in. Our CE 5.0 has it, Microsoft just took it out by default because some things don't work. We have plenty of components with ThreadingModel='Both'

I would suggest you develop an empty or dummy COM object specifically targetted at CE, using the EVC4 compiler (which is fussier than the regular VC compilers) to make sure you can get the infrastructure working. Once you've got a working shell you can port the useful code into it. You could always create a free threaded component and simply wrap every entry point with the same critical section so that old single threaded code can be used internally without breaking anything. It's not highly efficient but it should work.

Nothing is exactly what it seems but everything with seems can be unpicked.

Anyone knows a tool to find C style casts ?

sixio24-Jul-07 0:24

sixio

24-Jul-07 0:24

I'd like to have a reliable method to find C style casts in the source code. They can't be easily detected like 'static_cast' and the other C++ cast operators.
If there is a tool that can do the job, please point me to it.
Thanks in advance for your help.

Re: Anyone knows a tool to find C style casts ?

James R. Twine24-Jul-07 2:11

James R. Twine

24-Jul-07 2:11

A C-style cast is generally in the form of (type)ValueToCast. If you are looking for things like that for code-review purposes, also watch out for temporaries that are created using the following syntax: type(ValueToCast).

For example:

int iValueA = (int)dDoubleValue;
int iValueB = int( dDoubleValue );
 
FuncThatTakesACString( CString( "String Literal To Make A CString From" ) );

Things things should be rather easy to do a find-in-files search on, you can even automate VS using a macro to repeat the find using a list of types.

Peace!

Re: Anyone knows a tool to find C style casts ?

DevMentor.org25-Jul-07 9:39

DevMentor.org

25-Jul-07 9:39

That fine for intrinsic C++ type which you know exist, but how about users defined types, which you are not aware of? I think our friend wants a tool that will catch all the type cast.

Yours Truly, The One and Only!

Re: Anyone knows a tool to find C style casts ?

James R. Twine25-Jul-07 11:08

James R. Twine

25-Jul-07 11:08

   Simple - you run something like Doxygen or some other documentation tool to get you all of the types that are being used by your application. You then feed that into my suggestion above.

   Brute force, yes, but it works; especially when you do not what to pay money for a good code review/analysis. Hell, lint with the right rules may do it for you.

   Peace!

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