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i am currently following "C++ The complete reference by : Herbert Schildt"
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class staff {
string code, name;
public:
staff() : code(0000), name("Unknown") {}
You have declared code as a string, but you are passing a value of 0, which is a null pointer.
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Which is what the debugger would have shown you.
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Is it possible to link a DLL in another DLL and call its functions?
How can we do that?
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Yes, it's possible, and the same way that you access the functions of any DLL. But your question is not clear, what problem are you having.
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Hi All,
I am having Three Radio Buttons in a Dialog Based Application. The Name of the Radio Buttons are IDC_RADIO1,IDC_RADIO2 and IDC_RADIO3.
I have Grouped the First Radio Button IDC_RADIO1. I have Disabled the First Radio Button which is Grouped.
Now When I change the selection of First Radio Button to Second Radio Button I am getting Assertion. I have google and found that this a Microsoft Issue which is mentioned as same in this link.
[Q114980: FIX: Disabled DDX Radio Button Causes Infinite Loop | KnowledgeBase Archive]
https://jeffpar.github.io/kbarchive/kb/114/Q114980/
Let me know if any solutions regarding this.
Thanks in Advance
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janaswamy uday wrote: [Q114980: FIX: Disabled DDX Radio Button Causes Infinite Loop | KnowledgeBase Archive]
https://jeffpar.github.io/kbarchive/kb/114/Q114980/
Let me know if any solutions regarding this.
But it was very good written in the article you have mentioned!
Quote: RESOLUTION
To work around this problem, do one of the following:
- Arrange the group so that the first radio button is not disabled when any of
the other controls in the group are enabled.
-or-
- Call EnableWindow() to enable the radio button before DDX_Radio() is called
[for example, in DoDataExchange()].
-or-
- Write your own DDX_Radio() replacement, as shown in the sample code in the
"MORE INFORMATION" section, below.
STATUS
Microsoft has confirmed this to be a problem in Microsoft Foundation Classes,
versions 2.0 and 2.5. This problem was corrected in MFC version 3.0
MORE INFORMATION
One solution is to write your own DDX_Radio() replacement, which uses
::GetWindow() to iterate through all the controls on the dialog box until it
encounters one with style "WS_GROUP" or a handle of "NULL". The following sample
code is a substitute for DDX_Radio():
Sample Code
void AFXAPI DDX_MyRadio(CDataExchange* pDX, int nIDC, int& value)
{
HWND hWndCtrl = pDX->PrepareCtrl(nIDC);
ASSERT(::GetWindowLong(hWndCtrl, GWL_STYLE) & WS_GROUP);
ASSERT(::SendMessage(hWndCtrl, WM_GETDLGCODE, 0, 0L) &
DLGC_RADIOBUTTON);
if( pDX->m_bSaveAndValidate )
value = -1;
int iButton = 0;
do
{
if( ::SendMessage(hWndCtrl, WM_GETDLGCODE, 0, 0L) &
DLGC_RADIOBUTTON
)
{
if( pDX->m_bSaveAndValidate )
{
if( ::SendMessage(hWndCtrl, BM_GETCHECK, 0, 0L) != 0 )
{
ASSERT(value == -1);
value = iButton;
}
}
else
{
::SendMessage( hWndCtrl, BM_SETCHECK, (iButton == value), 0L
);
}
iButton++;
}
else
{
TRACE( "Warning: skipping non-radio button in group.\n" );
}
hWndCtrl = ::GetWindow( hWndCtrl, GW_HWNDNEXT );
} while(hWndCtrl!=NULL &&
!(GetWindowLong(hWndCtrl,GWL_STYLE)&WS_GROUP));
}
Remember to replace the following lines in your CDialog::DoDataExchange():
DDX_Radio(pDX, IDC_RADIO1, m_iRadio);
with:
DDX_MyRadio(pDX, IDC_RADIO1, m_iRadio);
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Hi I have worked but this is not working.
My Requirement is to Disable the Group Radio button but still I am getting Assertion even after doing with
//{{AFX_DATA_MAP(CMyDialog)
DDX_MyRadio(pDX, IDC_RADIO1, m_iRadio);
//}}AFX_DATA_MAP
and the below Function
// DDX_MyRadio(), which is a modified DDX_Radio().
//
void AFXAPI DDX_MyRadio(CDataExchange* pDX, int nIDC, int& value)
// must be first in a group of auto radio buttons
{
HWND hWndCtrl = pDX->PrepareCtrl(nIDC);
ASSERT(::GetWindowLong(hWndCtrl, GWL_STYLE) & WS_GROUP);
ASSERT(::SendMessage(hWndCtrl, WM_GETDLGCODE, 0, 0L) &
DLGC_RADIOBUTTON);
if( pDX->m_bSaveAndValidate )
value = -1; // value if none found
// walk all children in group
int iButton = 0;
do
{
if( ::SendMessage(hWndCtrl, WM_GETDLGCODE, 0, 0L) &
DLGC_RADIOBUTTON
)
{
// control in group is a radio button
if( pDX->m_bSaveAndValidate )
{
if( ::SendMessage(hWndCtrl, BM_GETCHECK, 0, 0L) != 0 )
{
ASSERT(value == -1); // only set once
value = iButton;
}
}
else
{
// select button
::SendMessage( hWndCtrl, BM_SETCHECK, (iButton == value), 0L
);
}
iButton++;
}
else
{
TRACE( "Warning: skipping non-radio button in group.\n" );
}
hWndCtrl = ::GetWindow( hWndCtrl, GW_HWNDNEXT );
} while(hWndCtrl!=NULL &&
!(GetWindowLong(hWndCtrl,GWL_STYLE)&WS_GROUP));
}
Thanks
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Then try to use another "workaround"!
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Hi Victor,
Could you please let me know the possible solution. This is very Urgent requirement to me.
Help me out please.
Thanks
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Try one of the other workarounds.
The difficult we do right away...
...the impossible takes slightly longer.
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There must be another reason for the assertion because you are very probable not using MFC 2.x shipped with the Microsoft C compiler versions 1.x:
Last Modified: 07-MAY-2001
-------------------------------------------------------------------------------
The information in this article applies to:
- The Microsoft Foundation Classes (MFC), used with:
- Microsoft Visual C++ for Windows, 16-bit edition, versions 1.0, 1.5
- Microsoft Visual C++, 32-bit Editions, version 1.0
Quote: Now When I change the selection of First Radio Button to Second Radio Button I am getting Assertion
How do you change the selection? Where does the assertion occur (MFC source file name, line, and in which function)?
Anyway, a radio button group is intended to have exactly one member checked. When activating a button, all other buttons will be unchecked. But a disabled button can't be checked or unchecked. If you need to disable a radio button, you must first ensure that it is not checked (usually by checking another button of the group).
The same applies when disabling a button in the template: It must not be set to checked.
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Hi Jochen Arndt,
Thank you very much for your support. I got it now and I am not getting any assertion after
"you must first ensure that it is not checked (usually by checking another button of the group)."
Thank you very much once again.
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We have a device that returns data from a 2D grid thus each data value is indexed by its row and column. The number of rows and columns is not fixed, as the device can be reconfigured, but in normal use the number of rows and columns does not change. We store the data values in memory for subsequent retrieval.
Our problem is how to convert a row + column pair {x,y} into an address in the memory. This sounds trivial:
offset = x * (total_number_of_columns) + y;
However, we have to do this very very quickly, and using as little processor power as possible. A multiplication is not good. We do not need to store the values contiguously as row, row, row etc. We do have limited memory so cannot be too wasteful.
One way is to store the data values in a grid whose number of columns is always a power of 2. Thus if our device generates 20 rows and 50 columns of data, we store them in a 20 rows by 64 columns grid. This means the data is not packed tightly in memory. To convert {x,y} into a memory location:
offset = x << 6 + y;
The quickest way I can think of is to use a look up table:
offset = lookup[x] + y;
Thus lookup is the offset to the start of each row in memory.
So, my question is how can we do this as fast and simply as possible? Is there a quicker way?
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The performance of integer multiplications depend on the used CPU architecture and generation.
With most x86 and compatible CPUs integer multiplications are 2 - 4 times slower than additions which can be usually ignored. Using a lookup table will be then not significantly faster or even slower.
However, with other (mainly RISC) CPU's, the operation can be up to 40 times slower than additions.
Quote: The quickest way I can think of is to use a look up table
The quickest way is using a shift operation because that is executed on registers while a lookup table requires loading from memory.
Just compare the methods (in pseudo code):
; Classic method
load r1, x
mul r1, total_number_of_columns
add r1, y
; Shift
load r1, x
shl r1, shift_count
add r1, y
; Lookup table
load r1, x
; Assuming item size is a power of 2
; Otherwise a multiplication is used here!
shl r1, sizeof(item)
; EDIT: Must be of course according to the table item size
shl r1, TABLE_ITEM_SIZE_SHIFT
load r1, [lookup_table + r1]
add r1, y Note that some of the above operations might require two assembly instructions (especially on RISC CPU's) when operations can be only performed on registers and not with memory addresses.
modified 29-Mar-18 9:00am.
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There may be, depending on the processor and number of columns and size of elements. Some processors give fast access to separate bytes of a register (or in the first place form a larger register by adjoining several smaller registers), then perhaps you can form an address almost for free by creating y in the low byte and x in the high byte of the address (likely with an offset otherwise the matrix has to start at 0). This applies to z80 and 8086 and probably some other old CISC architectures (not modern x86 though - it's still possible but no longer actually fast). On a RISC architecture that sort of trick usually doesn't exist. It also typically wastes a lot of memory (you can use the gaps of course but they're fragmented).
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Before using such micro-optimisations, I would ensure that we have used all higher-level optimisations, first. For example:
- How are the data received?
Are they stored in memory in order of reception, or does some processing (e.g. address calculation) need to be performed? - How are the data processed?
Is the access pattern sequential? random?
If a single pass through the data is performed, is it possible to store the data (see question 1 above) in the order of processing, and thereby avoid all indexing?
You may be able to think of other optimisations, based on your knowledge of the hardware and the problem.
Ad astra - both ways!
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Can you please suggest me Best Free tool to detect
1. Application Hang issues in C++ code
2. Memory leaks/ access violation
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Using Code Gear /RAD studio. Please advise
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I had a memory allocated out side a try block and I am trying to delete in finally?
Should there be any issue with this. I am getting access violation while deleting
char *heap = new char [50];
try
{
......
}
finally(...)
{
delete[] heap;
}
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It should work when not modifying (which includes deleting) the heap pointer inside the try block.
If you are not doing such (just comment the code inside the try block to check it), you should tell us which compiler you are using because finally is not defined by the C++ standard.
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I am using RAD Studio code gear
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