Subj : Multi-Thread and memory allocation error (or bug in 5.02).
To   : borland.public.cpp.borlandcpp
From : "Martin Catney" <m.catney@andor-tech.com>
Date : Fri Aug 29 2003 06:10 pm

I am experience some problems with Borland 5.02 with multitheads and memory
allocation and deallocation. The same code on Borland Builder 6 appears to
work fine. I have included an example program which creates multiple
instances of the same class then deletes them. The class constructor creates
a new thread and allocates a large block of memory while the destructor
deallocates the memory and terminates the thread.

I get an access violation at 0x634b5e: read of address 0x4cdc058 when I run
the example. This corresponds to the line
delete[] array;
in the class destructor. If the creation and termination of the threads is
removed the example runs fine.

Does anyone spot an obvious error in my example or is this a bug in the
Run-Time Library?

Regards
Martin


#include <windows.h>
#include <process.h>
//#include <iostream.h>

//#define ASIZE 159727
#define ASIZE 159727

void _USERENTRY ThreadFunction(HANDLE hEvent)
{
  WaitForSingleObject(hEvent, INFINITE);
}

class TVMImageList
{
public:
  TVMImageList(unsigned long noImages, unsigned long size);

  ~TVMImageList();

public:
 unsigned long mSize;
 unsigned long mLength;
  int* array;
  int** thearray;
  HANDLE hEvent;
  HANDLE mThread;
  unsigned long mThreadID;
};


TVMImageList::TVMImageList(unsigned long noImages, unsigned long size)
:mSize(size), mLength(noImages)
{
  hEvent = CreateEvent(NULL, FALSE, FALSE, NULL);

  mThread = (HANDLE)_beginthreadNT(
    ThreadFunction, // pointer to thread function
    4096,  // stack size
    hEvent, // argument for new thread
    NULL,
    0,
    &mThreadID
  );
  SetThreadPriority((void*)mThread,THREAD_PRIORITY_NORMAL);

  thearray = new int*[mLength];
  for (int i =0; i<mLength;i++)
    thearray[i] = new int[size];

  for (int j=0; j < mLength ; j++){
    array = thearray[j];
    for (int i=0;i<mSize;i++)
      array[i]=i;
  }
}

TVMImageList::~TVMImageList()
{
  SetEvent(hEvent);
  WaitForSingleObject(mThread, INFINITE);
  CloseHandle(hEvent);

  for (int j=0; j < mLength ; j++){
    array = thearray[j];
    for (int i=0;i<mSize;i++)
      if(array[i]!=i){};
//       cout << "Error";
  }
  for (int j=0; j < mLength ; j++){
    array = thearray[j];
    delete[] array;
  }
  delete[] thearray;
}



void main()
{
  TVMImageList* list = new TVMImageList(10, ASIZE);
  TVMImageList* list1 = new TVMImageList(10, ASIZE);
  TVMImageList* list2 = new TVMImageList(10, ASIZE);
  TVMImageList* list3 = new TVMImageList(10, ASIZE);
  TVMImageList* list4 = new TVMImageList(10, ASIZE);
  TVMImageList* list5 = new TVMImageList(10, ASIZE);
  TVMImageList* list6 = new TVMImageList(10, ASIZE);
  TVMImageList* list7 = new TVMImageList(10, ASIZE);

  delete list7;
  delete list6;
  delete list5;
  delete list4;
  delete list3;
  delete list2;
  delete list1;
  delete list;
//  delete list8;
}

.