C / C++ / MFC

1-Oct-07 17:50

I am making project in vc++ and i got problem of the unhandled violation in vc++ MFC.

whenever I create the object of other class in same class and then I use it for some operation then I got this error. My Error is like below.........

0xC0000005: Access violation reading location 0xccccccd0.

Plz kindly Reply me if you have any solution.

Thanks in Advance.

Ashish Bhatt

zakkas24831-Oct-07 18:06

1-Oct-07 18:06

Plz post Some code that u write in your application.
so i can help.
Smile | :)

hiren thakkar

ashishbhatt1-Oct-07 18:17

1-Oct-07 18:17

I have Classes like below

TestRTMPDlg ///Main Dialog class

RTMPBuffer
RTMPClient
RTMPSocket

When i declare object of RTMPBuffer class in RTMPClient class in header file and then I call the function of RTMPBuffer class then i got the run time error like.......

/////////////////////////////

Unhandled exception at 0x004196c8 in TestRTMP.exe: 0xC0000005: Access violation reading location 0xccccccd0.

//////////////////////////////////

Plz Reply yar if u got some solution.
ok bye.

Ashish Bhatt

Ontanggabe Parulian1-Oct-07 18:40

1-Oct-07 18:40

Probably you have a pointer variable which did not intialized properly. Or you try to copy variable to another variable which was not reserved using "new". Check your RTMPBuffer class.

Ian

zakkas24831-Oct-07 18:41

1-Oct-07 18:41

ashish , when u got the error then u got abort retry box. then click retry button then press
alt + 7 then u got call stack. click line in call stack one by one . then u got the line on which got error . send me that line.

if code is not large then mail me. i will check it.

hiren

zakkas24831-Oct-07 18:48

1-Oct-07 18:48

try this link this may be useful for u.
http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=1080309&SiteID=1[^]

send me the line on which u got the error.

hiren

Stephen Hewitt1-Oct-07 19:08

Stephen Hewitt

1-Oct-07 19:08

You've posted no source and no call stack; how can we possibly help given such limited data?

Steve

ashishbhatt1-Oct-07 19:10

1-Oct-07 19:10

////////////////RTMPClient.cpp/////////////////

#include "StdAfx.h"
#include "RTMPClient.h"
#include "RTMPBuffer.h"
#include "VSocket.h"

RTMPClient::RTMPClient(void)
{
//m_sock =NULL;
m_buff = new RTMPBuffer();
}

RTMPClient::~RTMPClient(void)
{
}
BOOL RTMPClient::SendRectangle(RECT &rect)
{
char str[100];
sprintf(str," In RTMPClient Bottom %d,Right %d",rect.bottom ,rect.right);
MessageBox(NULL,CString(str),CString("TestRTMP"),0);

RECT sharedRect;
{
//omni_mutex_lock l(m_regionLock);
//sharedRect = m_server->GetSharedRect();
}

sharedRect.left = 0;
sharedRect.top = 0;
sharedRect.right = 1280;
sharedRect.bottom = 1024;

BOOL res = IntersectRect(&rect, &rect, &sharedRect);

if(res)
{
sprintf(str," In RTMPClientBottom %d,Right %d",rect.bottom ,rect.right);
//MessageBox(NULL,CString(str),CString("TestRTMP"),0);

}

// Get the buffer to encode the rectangle

m_buff->TranslateRect(rect,m_sock,sharedRect.left,sharedRect.top);

//UINT bytes = m_buff->TranslateRect(rect,m_sock,sharedRect.left,sharedRect.top);

// Send the encoded data
// return m_socket->SendQueued((char *)(m_buffer->GetClientBuffer()), bytes);

return TRUE;
}

///////////////RTMPClient.h//////////////////////
#include "RTMPBuffer.h"
#include "VSocket.h"
#pragma once

class RTMPClient
{
public:
RTMPClient(void);
~RTMPClient(void);

BOOL SendRectangle(RECT &rect);

public:

RTMPBuffer *m_buff;
VSocket *m_sock;
};

Stephen Hewitt1-Oct-07 19:24

Stephen Hewitt

1-Oct-07 19:24

You haven't indicated where the crash is occuring! If you don't know run it in a debugger and find out.

Steve

ashishbhatt1-Oct-07 19:28

1-Oct-07 19:28

In RTMPClient.cpp file
Program Crash on this line.......

//////////////////////////////////

UINT bytes = m_buff->TranslateRect(rect,m_sock,sharedRect.left,sharedRect.top);

//////////////////////////////////

it shows the unhandled exception like below......

/////////////////////////////////////////

TestRTMP.exe: 0xC0000005: Access violation writing location 0xcccccccc.

//////////////////////////////////////

zakkas24831-Oct-07 19:26

1-Oct-07 19:26

on which line u got the error..

may be in this line?

m_buff->TranslateRect(rect,m_sock,sharedRect.left,sharedRect.top);

hiren

ashishbhatt1-Oct-07 19:30

1-Oct-07 19:30

yes on this line i got error

if i initialize it with new operator in constructor then also it gives same error.

zakkas24831-Oct-07 19:35

1-Oct-07 19:35

i think it is due to m_sock . which is not being initialize yet..
make simple function without any arument then try that function .i think u will defiantly not get any error.

Stephen Hewitt1-Oct-07 19:37

Stephen Hewitt

1-Oct-07 19:37

I can't see a memory write operation on this line. Show the call stack and the machine code around the crash.

Steve

David Crow2-Oct-07 2:28

David Crow

2-Oct-07 2:28

ashishbhatt wrote:
char str[100];
sprintf(str," In RTMPClient Bottom %d,Right %d",rect.bottom ,rect.right);
MessageBox(NULL,CString(str),CString("TestRTMP"),0);

May I suggest:

CString str;
str.Format(" In RTMPClient Bottom %d,Right %d", rect.bottom , rect.right);
AfxMessageBox(str);

ashishbhatt wrote:
m_buff->TranslateRect(rect,m_sock,sharedRect.left,sharedRect.top);

What is the value of m_buff at this point?

"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 read bytes from winsock efficiently

Cedric Moonen1-Oct-07 20:58

Cedric Moonen

1-Oct-07 20:58

I think the best advice one can give you is to learn to use your debugger. This kind of errors can be easily fixed and quite quickly if you know how to use the debugger (and certainly much faster than asking on a forum).

So, press F5 to start your debugger. You will be able to set breakpoints in your code with F9 (breakpoints are points in your program where the execution will stop, allowing you to inspect the variables). Then, first localize where the crash occurs (and the callstack can be usefull there) and then you can inspect the different variables to see if everything is as expected.

Cédric Moonen
Software developer

Charting control [v1.2]

Ontanggabe Parulian1-Oct-07 17:20

1-Oct-07 17:20

Dear all,

I am in project of developing ISO 8583 Client Simulator. I got a problem here about how to read response message from the host. The response can contain NULL character any where within the bytes sequence and I never know how long the message is. The only thing about to know the message length is I must read the first two bytes of the message. And the remaining bytes actually is the message it self. Now, I want to create a variable to save the message and I must reserver the memory using "new". But how can I reserve the memory exactly as the message length it self, while the only one way to know the message length is to read the first two bytes of the message.

I am waiting any one response soon.

Ian

chandu0041-Oct-07 19:27

chandu004

1-Oct-07 19:27

yah your problem seems to be solvable. even i faced the same problem few days ago.but some more details are required.
1.what could be the maximum length of a mesage.
2.as you said, first two bytes contain the message length, we can conclude that, the size cannot exceed 16 bits, i.e. 0xffff. did you try taking an array of that size and see?
like,
char data[0xffff].
3.if this is possible, then you can comfortably take an array and use a stack pointer, to find the end of the message.

Ontanggabe Parulian1-Oct-07 19:41

1-Oct-07 19:41

This is snippet of my codes:

void CIsoMsg::mfc_voidGetByteRq(char *ld_pchrDst)<br />
{<br />
	int ld_intByteRqLen;<br />
	ld_intByteRqLen = this->md_strCompIsoMsg.length() >> 1;<br />
<br />
	char *ld_pchrByteRq = new char[ld_intByteRqLen];<br />
	for(int i=0; i < ld_intByteRqLen; ld_pchrByteRq[i++]=0);<br />
	this->mfc_voidHex2Byte((char*)this->md_strCompIsoMsg.c_str(), ld_pchrByteRq, 0, ld_intByteRqLen);<br />
<br />
	int ld_intTCPByteRqLen = ld_intByteRqLen + 2;<br />
	char *ld_pchrTCPByteRq = new char[ld_intTCPByteRqLen];<br />
	<br />
<big>	if(ld_intByteRqLen <= 255)<br />
	{<br />
		ld_pchrTCPByteRq[0] = 0;<br />
		ld_pchrTCPByteRq[1] = ld_intByteRqLen;<br />
	}<br />
	else<br />
	{<br />
		ld_pchrTCPByteRq[0] = ld_intByteRqLen / 256;<br />
		ld_pchrTCPByteRq[1] = ld_intByteRqLen % 256;<br />
	}</big><br />
	for(int i=2, j=0; i < ld_intTCPByteRqLen; i++, j++)<br />
	{<br />
		ld_pchrTCPByteRq[i] = ld_pchrByteRq[j];<br />
	}<br />
	<br />
	memcpy(ld_pchrDst, ld_pchrTCPByteRq, ld_intTCPByteRqLen);<br />
<br />
	delete [] ld_pchrByteRq;<br />
	delete [] ld_pchrTCPByteRq;<br />
}<br />
<br />
<br />
void CIsoMsg::mfc_voidHex2Byte(char *ld_pchrScr, char *ld_pchrDest, int ld_intStartOffset,int ld_intLen)<br />
{<br />
	char ld_chrBuf1[2], *ld_pchrBuf2;<br />
	ld_chrBuf1[1]=0;<br />
	int ld_intShiftLeft;<br />
	for(int i=0; i < (ld_intLen * 2); i++)<br />
	{<br />
		if(i%2 == 1) ld_intShiftLeft = 0; <br />
		else ld_intShiftLeft = 4;<br />
		ld_chrBuf1[0] = ld_pchrScr[ld_intStartOffset+i];<br />
        ld_pchrDest[i>>1] =  ld_pchrDest[i>>1] | strtol(ld_chrBuf1,&ld_pchrBuf2,16) << ld_intShiftLeft;<br />
	}<br />
}

There are two function I attached here. The length of those message (the first two bytes) is not as simple like the maximum is 0xffff. But it use the algorithm which I show you above (BIG formatted).
So I can't know the exactly length by conclude it would be 0xffff length.

Ian

Re: (Revision)How to read bytes from winsock efficiently

chandu0041-Oct-07 19:48

chandu004

1-Oct-07 19:48

can you just comment your code and repost it.
meanwhile, i will try to hand run it.

Ontanggabe Parulian1-Oct-07 20:17

1-Oct-07 20:17

Sory, here I repost the source code again cause the previous is not complete. The source code here is modified from the previous so you can run it on your machine. The certain variables here I initialized so it meet the testing environment that I used.

void main()<br />
{<br />
int ld_intByteRqLen;<br />
<br />
// ld_strCompIsoMsg is the actual message<br />
string ld_strCompIsoMsg("600015800002003020058020C010040010000000000333000002500021001500325577911013392824D12041011646435036343333373730313030303030303039323739393435357556C9933721414F0006303030333539");<br />
ld_intByteRqLen = ld_strCompIsoMsg.length() >> 1;<br />
<br />
char *ld_pchrByteRq = new char[ld_intByteRqLen];<br />
for(int i=0; i < ld_intByteRqLen; ld_pchrByteRq[i++]=0);<br />
<br />
// Convert the actual message to Byte<br />
this->mfc_voidHex2Byte((char*)this->md_strCompIsoMsg.c_str(), ld_pchrByteRq, 0, ld_intByteRqLen);<br />
<br />
// ld_intTCPByteRqLen added by 2 caused the first two bytes contain the message length<br />
int ld_intTCPByteRqLen = ld_intByteRqLen + 2;<br />
<br />
// ld_pchrTCPByteRq is the final message that will be passed through the network<br />
char *ld_pchrTCPByteRq = new char[ld_intTCPByteRqLen];<br />
<br />
// Here the algorithm of how the first two bytes save the message length<br />
if(ld_intByteRqLen <= 255)<br />
{<br />
ld_pchrTCPByteRq[0] = 0;<br />
ld_pchrTCPByteRq[1] = ld_intByteRqLen;<br />
}<br />
else<br />
{<br />
ld_pchrTCPByteRq[0] = ld_intByteRqLen / 256;<br />
ld_pchrTCPByteRq[1] = ld_intByteRqLen % 256;<br />
}<br />
<br />
// I concatenate the ld_pchrByteRq to the ld_pchrTCPByteRq<br />
// Using looping cause I can't use strcat while the string value contain NULL<br />
for(int i=2, j=0; i < ld_intTCPByteRqLen; i++, j++)<br />
{<br />
ld_pchrTCPByteRq[i] = ld_pchrByteRq[j];<br />
}<br />
<br />
// The TCPByteRq is the message that will be passed through the network<br />
// Here I printed its contain using loop for ant type cast to int (cause it can contain NULL)<br />
for(int i=0; i < ld_intTCPByteRqLen; i++) cout << "ld_pchrTCPByteRq[" << i << "] = " << (int)ld_pchrTCPByteRq[i] << endl;<br />
<br />
delete [] ld_pchrByteRq;<br />
delete [] ld_pchrTCPByteRq;<br />
}<br />
<br />
void mfc_voidHex2Byte(char *ld_pchrScr, char *ld_pchrDest, int ld_intStartOffset,int ld_intLen)<br />
{<br />
char ld_chrBuf1[2], *ld_pchrBuf2;<br />
ld_chrBuf1[1]=0;<br />
int ld_intShiftLeft;<br />
for(int i=0; i < (ld_intLen * 2); i++)<br />
{<br />
if(i%2 == 1) ld_intShiftLeft = 0; <br />
else ld_intShiftLeft = 4;<br />
ld_chrBuf1[0] = ld_pchrScr[ld_intStartOffset+i];<br />
ld_pchrDest[i>>1] = ld_pchrDest[i>>1] | strtol(ld_chrBuf1,&ld_pchrBuf2,16) << ld_intShiftLeft;<br />
}<br />
}

Ian

obviously 0xffff, i.e 65535.

David Crow2-Oct-07 2:30

David Crow

2-Oct-07 2:30

chandu004 wrote:
1.what could be the maximum length of a mesage.

What's the maximum value that two bytes can hold? Roll eyes | :rolleyes:

"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

chandu0042-Oct-07 2:38

chandu004

2-Oct-07 2:38

obviously 0xffff, i.e 65535.
any thing wrong? Rose | [Rose]