C / C++ / MFC Discussion Boards

Re: VC6 - bug - I desparately need advice

Stephen Muccione14-Jan-05 1:52

14-Jan-05 1:52

Try disabling optimizations using pragma's and sucessively narrow down the area where optimizations are disabled until you can isolate the line that the problem is on... then either fix the issue by re-writing the line or simply leave optimizations disabled for that specific line.

steve

pointer declaration

Oriented13-Jan-05 12:38

Oriented

13-Jan-05 12:38

1. what are the differences among:
CString* str;
,
CString *str;
and
(CString*) str;
?!
2. what are LPVOID,LPCTSTR,LPTSTR,LPARAM...
(u may give me a link)
thx

Re: pointer declaration

Michael Dunn13-Jan-05 12:58

Michael Dunn

13-Jan-05 12:58

These two mean the same thing:

CString* str;
CString *str;

Since whitespace is not important, they have the identical meaning. The first one is more common among C++ programmers, while the second way is more common among old-school C programers.
This:

(CString*) str;

is not a declaration at all. It's an expression statement that casts str to CString* and then throws away the result.

--Mike--
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Re: pointer declaration

LighthouseJ13-Jan-05 13:00

LighthouseJ

13-Jan-05 13:00

1. There is no difference between the first and second declarations, but the third, you are casting str, whatever it is, as a CString and therefore is dissimmilar.

2. Those are data types that are all pointers to established types. LPVOID is a pointer to any type of data. LPCTSTR translates to an LPCWSTR (constant null-terminated string of 16-bit Unicode characters) if UNICODE is defined, else it defaults to constant null-terminated 8-bit Windows ANSI characters, in other words, if UNICODE is define, you'll get a wider string. LPARAM is a message parameter. I paraphrased from a Windows Data Types page in this Visual Studio .NET help file, not a website.

If anyone wants to correct something or add, be my guest.

Re: pointer declaration

samson197813-Jan-05 14:52

samson1978

13-Jan-05 14:52

i think the two replies above this one has done question 1 enough justice.
as for LPVOID, LPCTSTR, LPTSTR, LPARAM and so on... they are Microsoft
defined macros of otherwise basic types... think of it this way....

L = LONG = long
P = represents the * (pointer)
LP = pointer of size long
VOID = void
C = const
T = TCHAR
TCHAR = char or wchar_t depending on if the UNICODE macro is defined
STR = string
PARAM = parameter

so LPVOID is just (long) pointer to void/anything
LPCTSTR is just a (long) pointer to a const string of type TCHAR

for more Microsoft defined types lookup "Windows Data Types"

Cheers

Re: pointer declaration

Ryan Binns13-Jan-05 17:47

Ryan Binns

13-Jan-05 17:47

Actually, LPVOID and PVOID are the same thing. The L doesn't mean anything any more, and is simply a hangover from the 16-bit DOS/Windows days. Back then:

PVOID was a NEAR pointer that pointed to an address in the same segment and required 16 bits of storage
LPVOID was a FAR pointer that could point to anywhere in the memory address space and required 32 bits of storage

Under Win32, there is no concept of NEAR and FAR pointers since the address space is a flat 32-bit address space and segments are not required.

Ryan

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Re: pointer declaration

toxcct13-Jan-05 22:31

toxcct

13-Jan-05 22:31

Sawjai wrote:
i think the two replies above this one has done question 1 enough justice.
as for LPVOID, LPCTSTR, LPTSTR, LPARAM and so on

and i'd conclude by saying :

<font color=#0000FF>typedef void</font>*        LPVOID;
<font color=#0000FF>typedef const</font> TCHAR* LPCTSTR;
<font color=#0000FF>typedef</font> TCHAR*       LPTSTR;
<font color=#0000FF>typedef</font> DWORD        LPARAM;
<font color=#008000>//...</font>
<font color=#0000FF>#ifdef</font> _UNICODE
    <font color=#0000FF>#define</font> TCHAR wchar_t;
<font color=#0000FF>#else</font>
    <font color=#0000FF>#define</font> TCHAR <font color=#0000FF>char</font>;
<font color=#0000FF>#endif</font>

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[toxcct][VisualCalc]

CString Problem

Dody_DK13-Jan-05 12:33

Dody_DK

13-Jan-05 12:33

I was reading the following article http://codeproject.com/clipboard/archerclipboard1.asp[^]

and when I compile the code, it give me an error
(error C2039: 'GetWindowTextA' : is not a member of 'CString')

and it says "see declaration of 'CString'"

any help with this?

thanks in advance

Re: CString Problem

ThatsAlok13-Jan-05 18:59

ThatsAlok

13-Jan-05 18:59

Dody_DK wrote:
I was reading the following article http://codeproject.com/clipboard/archerclipboard1.asp[^]

is not opening on my Ccomputer , i don't knwo why.

Dody_DK wrote:
and when I compile the code, it give me an error
(error C2039: 'GetWindowTextA' : is not a member of 'CString')

and it says "see declaration of 'CString'"

GetWindowText it Self a Win32 Api,search for it in your local copy of MSDN

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Re: CString Problem

Aamir Butt13-Jan-05 20:30

Aamir Butt

13-Jan-05 20:30

Better ask article related questions in their own forums/Message Boards. People dont like it here generally as you would have noticed by now.

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Re: CString Problem

toxcct13-Jan-05 22:40

toxcct

13-Jan-05 22:40

it seems like you call something like CString::GetWindowText().

you probably have a such lines :

CString str;
str.GetWindowText();

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

Re: CString Problem

Iain Clarke, Warrior Programmer14-Jan-05 0:34

Iain Clarke, Warrior Programmer

14-Jan-05 0:34

As others have said, questions about code in an article are best put in that article.

But I'm in a good mood.

Search MSDN for GetWindowText for all the answers you can shake a stick at.

GetWindowText is either a windows API function:
int GetWindowText( HWND hWnd, LPTSTR lpString, int nMaxCount );
Or a member function of CWnd:
int GetWindowText( LPTSTR lpszStringBuf, int nMaxCount ) const;
void GetWindowText( CString& rString ) const;

You can see the last member function takes a parameter of CString.
CString has no member function GetWindowText.

So in your code you probably have

CString str;
....
str.GetWindowText (...);

which should be:

void CMyWnd::OnSomething (...)
{
    CString str;
    ....
    GetWindowText (str);
    ....
}

Iain.

Re: CString Problem

Dody_DK15-Jan-05 0:40

Dody_DK

15-Jan-05 0:40

oki guys, since it is not the right place, so I would not talk more about it... and sorry if that disturbed you... thanks alot

Status Bar (continued)

LighthouseJ13-Jan-05 12:33

LighthouseJ

13-Jan-05 12:33

I took advice from Antony M Kancidrowski and changed my class to look like:

class C489guiApp: public CWinApp {<br />
public:<br />
	BOOL InitInstance()	{<br />
		m_pMainWnd = new C489guiFrame;<br />
		m_pMainWnd->ShowWindow(SW_SHOW);<br />
		m_pMainWnd->UpdateWindow();<br />
<br />
		pFrame = reinterpret_cast<C489guiFrame*>(m_pMainWnd);<br />
		ASSERT(pFrame != NULL);<br />
<br />
		return TRUE;<br />
	}<br />
	C489guiFrame* pFrame;<br />
	...<br />

It compiles but I get a runtime error:

Unhandled exception at 0x7c224c6c (mfc70d.dll) in 489gui.exe: 0xC0000005: Access violation reading location 0x0000000c.

The line it points to is an if statement:

if (!(pSBP->nFlags & SBPF_UPDATE) &&
	((lpszNewText == NULL && pSBP->strText.IsEmpty()) ||
	 (lpszNewText != NULL && pSBP->strText.Compare(lpszNewText) == 0)))

and then it returns true if that if statement is true, the arrow points to the last line. Am I not doing something else correctly? As before, I'm new to this so be gentle on my comprehension, thanks a lot in advance.

Re: Status Bar (continued)

KaЯl14-Jan-05 2:16

KaЯl

14-Jan-05 2:16

I think that you use a variable which isn't initialized. Is pSBP correctly set before using it? Was lpszNewText correctly initialized?

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Scrollbars in a Dialog

dlarkin7713-Jan-05 9:52

dlarkin77

13-Jan-05 9:52

Hi,

Can anybody help me out with this strange problem?

I have a dialog-based application. On the main dialog I have a CRichEditCtrl that I read the contents of a file into it.
The CRichEditCtrl has the Horizontal scroll, Vertical scroll, Auto HScroll and Auto VScroll properties set to true.

Whenever I use the vertical scrollbar, it automatically scrolls back to the top after about 5 seconds. Any suggestions as to what might be the cause of this?

Thanks very much,

dlarkin77 Confused | :confused:

Re: Scrollbars in a Dialog

Shog⁹13-Jan-05 11:46

Shog⁹

13-Jan-05 11:46

What else is going on in your dialog? Do the contents change over time? Are there user-defined messages being sent to/from it? Spy++ is your friend: what messages coincide with the reverted scrolling?

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Re: Scrollbars in a Dialog

dlarkin7714-Jan-05 7:25

dlarkin77

14-Jan-05 7:25

Thanks for the reply Shog9. Smile | :)

I found what was causing the problem. It was actually an error on my part. D'Oh! | :doh:

dlarkin77

VC++6 + VS SP6 = COMPUTATION BUG!!

Fred D.13-Jan-05 6:23

Fred D.

13-Jan-05 6:23

Hi guys,

PC : Intel PIII 700MHz with W2k SP6

I was using VC++ 6 with VisualStudio SP4 and the result of a calculation like this one..

double res = 25.5/1000; // would give you 0.025500000000, as you can expect..

Now, here’s something quite weird:
I’ve just upgraded VS to SP6 and the same calculation now gives me..

double res = 25.5/1000; // 0.025499999999999998 ????? D'Oh! | :doh:

even worse if you write:
double t2 = 5.f*0.001f; // 0.0050000002374872565 :wtf:

And it seems to be like that every time you try to compute 2 doubles or a double and an int for ex. (multiplication or division !)

as anyone noticed something similar? Wonder if there is any fix for that one.

Tx
Fred

Re: VC++6 + VS SP6 = COMPUTATION BUG!!

PJ Arends13-Jan-05 6:46

PJ Arends

13-Jan-05 6:46

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccore/html/_core_Why_Floating_Point_Numbers_May_Lose_Precision.asp[^]

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Re: VC++6 + VS SP6 = COMPUTATION BUG!!

Antony M Kancidrowski13-Jan-05 6:52

Antony M Kancidrowski

13-Jan-05 6:52

Fred D. wrote:
Wonder if there is any fix for that one

I doubt it. What you have stumbled across is inevitable with floating point arithmetic.

You need to decide what precision you want and round up to that precision after your calculation. You can then show the floating point number to the precision required.

e.g.

double res = 25.5/1000 + 0.0005;

for your example.

Ant.

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I'm coloured, yet clear.
I'm fruity and sweet.
I'm jelly, what am I? Muse on it further, I shall return! - David Walliams (Little Britain)

Re: VC++6 + VS SP6 = COMPUTATION BUG!!

Fred D.13-Jan-05 7:33

Fred D.

13-Jan-05 7:33

tx for your reply,

in your example it would actually be like that:
Double t = (25.5+0.0005)/1000; // but that still gives 0.025500499999999999 :doh:

but actually, it seems it be a display issue in the debugger viewer..
'cos even when the debugger shows a value d = 0.025500000001 where it should be 0.025500000000 when compare d with 0.025500000000, the result is true.

and a further check at the @ of the variable in the memory window, shows a correct value. TK GOD! Big Grin | :-D

Fred

Re: VC++6 + VS SP6 = COMPUTATION BUG!!

Antony M Kancidrowski13-Jan-05 12:56

Antony M Kancidrowski

13-Jan-05 12:56

Yes you still will not have the correct answer to all those decimal places. The idea is that the answer is correct to the precision that you choose. In this case 4 decimal places.

You are quite correct in the matter of it being a display issue thereafter.

Ant.

I'm hard, yet soft.
I'm coloured, yet clear.
I'm fruity and sweet.
I'm jelly, what am I? Muse on it further, I shall return! - David Walliams (Little Britain)

How to Run a executable file using c++ program

Aqueel13-Jan-05 3:56

Aqueel

13-Jan-05 3:56

Hi friends
How can i run a executable file i.e. "abc.exe" using a c++ program.
Please help me.

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Re: How to Run a executable file using c++ program

Budric B.13-Jan-05 4:13

Budric B.

13-Jan-05 4:13

system("abc.exe");

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.