Memory Leak

[saravanaram]

Hi all, in mfc dialog based application i have the following function. void Reverse() { // TODO: Add your control notification handler code here int nIndex, nStrLength, nWordIndex; TCHAR *pStrWord, *pStrFinal, ch; UpdateData(TRUE); nStrLength = m_strInput.GetLength(); pStrWord = new TCHAR [nStrLength + 1]; pStrFinal = new TCHAR [nStrLength + 1]; *pStrWord = '\0'; *pStrFinal = '\0'; nWordIndex = 0; for (nIndex = 0;nIndex < nStrLength; nIndex++) { ch = m_strInput.GetAt(nIndex); if ( ch != ' ' || nIndex == nStrLength ) { pStrWord[nWordIndex] = m_strInput.GetAt(nIndex); nWordIndex++; } if ( ch == ' ' ) { pStrWord[nWordIndex++] = ' '; pStrWord[nWordIndex] = '\0'; _tcscat(pStrFinal,_tcsrev(pStrWord)); nWordIndex=0; } if ( nIndex == (nStrLength - 1) ) { pStrWord[nWordIndex++] = ' '; pStrWord[nWordIndex] = '\0'; _tcscat(pStrFinal,_tcsrev(pStrWord)); nWordIndex = 0; } } pStrFinal = _tcsrev(pStrFinal); pStrFinal[nStrLength] = '\0'; m_strOutput = pStrFinal; UpdateData(FALSE); delete [] pStrWord; delete [] pStrFinal; } I get error when deleting pStrFinal could anyone tell me why this happens. can any one of you explain me how to dump memory and to verify it.

[Stephane Rodriguez]

With pStrFinal = _tcsrev(pStrFinal);, you are messing your pointer away. I recommend to use the MFC CString class instead (since you said it's a MFC dialog). This hides all this memory allocation mess.

[Hari Krishnan Noida]

Hi, Regarding the technique of dumping in-memory statistics, is given below Note: memstate1 takes snapshot of pre-memory leak and memstate2 takes snapshot of post-memory leak. finally, memstate3 makes the statistics based on both the snapshots. CMemoryState memState1, memState2, memState3; void CHello::MakeMemoryLeak() { memState1.Checkpoint(); LPCTSTR strMemoryLeak = new char[50]; memState2.Checkpoint(); memState3.Difference(memState1, memState2); memState3.DumpStatistics(); } Hope this Helps Regards ~Hari~

[David Crow]

saravanaram wrote: I get error when deleting pStrFinal... So what's the error? I suspect the problem lies within the following line, but can't know for sure without stepping through the code. pStrFinal = _tcsrev(pStrFinal);

[Hari Krishnan Noida]

Hi David, if you see the memory contents of (pStrWord), it contains 5 (CD - valid memory allocated) and 4 FD(padded memory, # may differ) (Note: Assume that nStrLength is 5) Following code lines, are writing on unallocated memory. pStrWord[nWordIndex++] = ' '; //This causes the problem. pStrWord[nWordIndex] = '\0'; _tcscat(pStrFinal,_tcsrev(pStrWord)); as well, pStrFinal = _tcsrev(pStrFinal); //This assignment also causes the problem. Actually, he has to allocate the extra one byte of memory to put the space character (' '). Hopefully, I am right. regards ~Hari~

[David Crow]

Good observation.