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I have found a very interesting incident of memory leak in my code. Although I have not been able to find the root cause of the leak still thought to share with you all. I will really appreciate any help on this. I am rather curious to know how come a memory leak can be seen in use of CString in such a simple way.
Code:
We have a thread function:
UINT __cdecl LogWriteThread(void *pParam)
{
CLog* pLog = (CLog*)pParam;
UNUSED_ALWAYS(pParam);
try
{
pLog->LogWriteFunc();
}
.................
.................
return 0;
}
UINT __cdecl CLog::LogWriteFunc(void *pParam)
{
..........
CString cstrLogDataBuffer = m_cstrLogLine;
m_cstrLogLine = _T("");
CopyLogToFileByThread(cstrLogDataBuffer);
}
void CMpmLog::CopyLogToFileByThread(const CString& cstrLogDataBuffer)
{
....................
const long iLength = cstrLogDataBuffer.GetLength();
char *pBuffer = new char[iLength + 1];
for (long iIndex = 0;iIndex < iLength; iIndex++)
{
pBuffer[iIndex] = (char)cstrLogDataBuffer.GetAt(iIndex);
}
pBuffer[iLength] = '\0';
const unsigned int uiWriteLen = fwrite((const void *)pBuffer, sizeof(char),iLength, m_pofLogStream);
delete[] pBuffer;
....................
}
========================
If I commment call for "CopyLogToFileByThread" in function LogWriteFunc then memory leak goes away. But thats not the solution.
Manoj
Never Gives up
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The shown code part of CopyLogToFileByThread() does not change a CString object. So this can't be the source of the leak it is from a CString object.
It seems that you are accessing the m_strLogLine CString object by multiple threads. When doing so, you must use locking. To do so, you may add a CCriticalSection member to your class and use this for locking:
CSingleLock singleLock(&m_CritSection);
singleLock.Lock();
CString cstrLogDataBuffer = m_cstrLogLine;
m_cstrLogLine = _T("");
singleLock.Lock();
Use similar code when changing or reading m_strLogLine anywhere.
One more note:
Instead of converting a TCHAR string to char by casting each char, you may use WideCharToMultiByte() or the conversion provided by CString:
CStringA strLineA(cstrLogDataBuffer.GetString());
fwrite(strLineA.GetString(), sizeof(char), strLineA.GetLength(), m_pofLogStream);
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Thanks Jochen for your inputs.
1. I have used CriticalSection while accessing m_cstrLogLine but have omitted those additional lines to focus on actual business logic.
2. I agree that WideCharToMultiByte() could have been a better option to convert string but I have changed code to rule out any leak during conversion itself.
3. The CopyLogToFileByThread() is not modifying string and thats why its surprising to have memory leak from that function.
4. One more point i will like to mention here is thhat this application has been built for WinCE 6.0.
I am trying to replicate the same issue with a test application and if possible for XP.
Manoj
Never Gives up
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Manoj Kumar Rai wrote: I have found a very interesting incident of memory leak in my code.
How are you verifying this?
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"Show me a community that obeys the Ten Commandments and I'll show you a less crowded prison system." - Anonymous
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POINT Point;
::GetCursorPos(&Point);
HWND hWnd = ::WindowFromPoint(Point);
::PostMessage(hWnd, WM_KEYDOWN, 'a', NULL);
I sent a message WM_KEYDOWN to hWnd.
It is activate on Windows Notepad..
but on games like need for speed, it isn't activate..
how do i do?
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Thats because it probably doesn't use the windows message pump for keyboard and mouse interaction.
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Games like need for speed doesn't use the usual windows messages system. Your application responds when your window gets the message through WindProc and the message loop. The way which is used in games is entirely different.
A cool video :- http://www.youtube.com/watch?v=XLCe-hQ8lgE[^]
"If A is a success in life, then A=x+y+z. (Work is x; y is play; and z is keeping your mouth shut.)"
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Hello!
I had an error in my project created with QT and C++
I created Server which gets data from AudioInput and gives it to UDP Socket, there is no problem, but in Client's project I had a problem, when I tried to write data to AudioOutput device after UDP Socket gets this data from net
in my project error was in this line "int l = audioSource->read(audioBuffer,input);" in
"qaudiooutput_win32_p.cpp"
and this is Call Stack at time debugging which shows this
QtMultimediad4.dll!QAudioOutputPrivate::deviceReady() Line 579 + 0x1c bytes C++
QtMultimediad4.dll!QAudioOutputPrivate::qt_static_metacall(QObject * _o=0x00b53308, QMetaObject::Call _c=InvokeMetaMethod, int _id=1, void * * _a=0x00b51d20) Line 52 + 0x8 bytes C++
what I did wrong
PLEASE HELP!!!!! 
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Mkhitar Sargsyan wrote: what I did wrong
You forgot to tell us what the error was.
And please use <pre> tags around your code so it is readable, like so:
int l = audioSource->read(audioBuffer,input);
Veni, vidi, abiit domum
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I wrote this code.
QByteArray getdata;
getdata.resize(socket->pendingDatagramSize());
socket->readDatagram(getdata.data(),getdata.size(),&senderaddres,&senderport);
then
qbufferout.open(QIODevice::ReadWrite);
audioOutput->start(ioDeviceout);
qbufferout.write(getdata);
qbufferout.close();
but I have got error at time this function "qbufferout.write(getdata);" and error goes to this line
"int l = audioSource->read(audioBuffer,input);" this line is in the "qaudiooutput_win32_p.cpp"
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Well you still have not used <pre> tags round your code. And you still have not told us what the error is.
Veni, vidi, abiit domum
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I don't know how use this
tags
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Select your code and click on the code button above the edit box.
Veni, vidi, abiit domum
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how can I post here picture???????????
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You can't; just post the lines of code, indicate the line where the error occurs, and show the complete error message. It's only a simple matter of copy and paste.
Veni, vidi, abiit domum
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void networking::Resive()
{
QByteArray getdata;
getdata.resize(socket->pendingDatagramSize());
socket->readDatagram(getdata.data(),getdata.size(),&senderaddres,&senderport);
qbufferout.open(QIODevice::ReadWrite);
audioOutput->start(ioDeviceout);
qbufferout.write(getdata);
//after this line it hase got error and goes to this one "int l = audioSource->read(audioBuffer,input)" //this isn't my code. it is code of QT
qbufferout.close();
}
and error message is it:
"First-chance exception at 0x586d997a in networking.exe: 0xC0000005: Access violation reading location 0xab216d6b."
and call stack shows this:
"QtMultimediad4.dll!QAudioOutputPrivate::deviceReady() Line 579 + 0x1c bytes "
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Access violation means that it is trying to read a memory location that is not part of the application's address space. The only way to diagnose such an error is to step through the code with your debugger and see where the bad address is getting set, or where a good address is getting overwritten.
Veni, vidi, abiit domum
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I have a simple project that compiles in VS2005. When I compile it in VS10, I get assertion errors in the file bcmenu.cpp. bcmenu.cpp was taken from this project
http://www.codeproject.com/Articles/22/Cool-Owner-Drawn-Menus-with-Bitmaps-Version-3-03
The first few comments on that link talk about the project not working for Windows XP if compiled in VS10. Any chance, anyone else has come across this and has a solution? I see the comments but my project compiles in VS10, runs fine on Vista, 7, & 8 but crashes on XP and I cant figure out from the comments what Im doing wrong.
Please let me know. If you have a revised bcmenu.cpp file that you can email me, that would be great.
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There are some suggestions in the first message thread at the end of the article.
Veni, vidi, abiit domum
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havnig see a lot sample codes about c++11 thread like
// thread t;
if(t.joinable()){
t.join()
}
is it possible that t terminate after the if(...) test,which will result in a error when call t.join() , especially in the context of concurrency
appreciate for reading
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It is possible that the thread actually finishes/terminates between the if and the join but it won't cause an error. Even if the thread terminates the kernel maintains the thread handle and/or a result object (with the thread exit code) that can be waited (and queried for the exit code). If the thread has already terminated when you call join then join returns immediately without problems.
EDIT: some additional qotes from http://en.cppreference.com/w/cpp/thread/thread/joinable[^]
"A thread that has finished executing code, but has not yet been joined is still considered an active thread of execution and is therefore joinable."
On windows (Winapi thread functions) you can have multiple handles to the same thread and when the thread terminates all handles become signaled and you can wait any of the handles any number of times until closing the handles. On unix like systems the pthread api is more restrictive: you get a thread handle when you create a (non-detached) thread and you have to wait exactly once and only once for the thread handle. If you don't wait for the thread handle then it causes a leak, if you wait for it multiple times then its an error. Waiting for it once gets the exitcode from the temp object (associated with the thread handle) and also frees this temp object.
Both behaviors can be simulated by a framework but C++11 chose something that is near to the unix philosophy (as implementing that on all platforms is simpler and more performant and usually enough).
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Hi,
i have this Problem in custom CHeaderCtrl control.
My message map look like this:
<br />
BEGIN_MESSAGE_MAP(CHeaderCtrlEx, CHeaderCtrl)<br />
ON_WM_LBUTTONDOWN()<br />
ON_WM_MOUSEMOVE()<br />
ON_WM_LBUTTONDBLCLK()<br />
ON_REGISTERED_MESSAGE(WM_HDN_ENDDRAG, OnHdnEndDrag)<br />
END_MESSAGE_MAP()<br />
Now i want to send a message to this header control but they never received it,
i never had this before so i don't know what cause this?
In a example Project here from codeproject work this "custom header control" very nice, no problems, only in my project?
So what to check, where can be my mistake, what im doing wrong??
Thanks for any help!
regards
bosfan
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Hi,
thans for Answer, yes i have all in my class definition.
It is the same project from:
Here in Codeproject
If i start this example all works fine, but not if i use this
in a new project.
Thanks
bosfan
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bosfan wrote: It is the same project from:
Here in Codeproject
It may be worth talking to the author then.
bosfan wrote: If i start this example all works fine, but not if i use this
in a new project.
Check what you have done that is different, it may help to diagnose the problem.
Veni, vidi, abiit domum
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