Thread: illegal operation

I'm working on a small program to test some file i/o. I have a class (CMything):

Code:

class CMything
{
private:
  long l1;
  long l2;
  long l3;
  RECT rc;
  char cC[30];
public:
  CMything();
  void Setl1(long lNew);
  long Getl1();
  void Setl2(long lNew);
  long Getl2();
  void Setl3(long lNew);
  long Getl3();
  void SetRC(long lL, long lT, long lR, long lB);
  LPRECT GetRC();
  void SetCC(char cNew[30]);
  char* GetCC();
  ~CMything();
};

Pretty simple and straight forward. Just a generic object that I can use in my file read/write ops. I have an array of 5 of these objects. I have 4 functions: 1 to fill the objects with data, 1 to write the data to a file, 1 to read the data in from a file and 1 to display the data read in so I can make sure everything went ok.

Code:

CMything cmThing[5];

void FillData()
{
   for(lCount=0;lCount<5;lCount++)
   {
     cmThing[lCount].SetCC("Jeff Lenoce");
     cmThing[lCount].Setl1(lCount*2);
     cmThing[lCount].Setl2(cmThing[lCount].Getl1()+1);
     cmThing[lCount].Setl3(cmThing[lCount].Getl2()+1);
     cmThing[lCount].SetRC(0,0,32,32);
   }
}

void SaveData()
{
   lSize=sizeof(CMything);
   ULONG fp=0;
   HANDLE hFile=CreateFile("cmThings.dat",GENERIC_WRITE,0,NULL,OPEN_ALWAYS,FILE_ATTRIBUTE_NORMAL,NULL);
   for(lCount=0;lCount<5;lCount++)
   {
    fp=lCount*lSize;
    WriteFile(hFile,&cmThing[lCount],lSize,&fp,NULL);
   }
  CloseHandle(hFile);
}

void ReadData()
{
  lSize=sizeof(CMything);
  ULONG fp=0;
  HANDLE hFile=CreateFile("cmThings.dat",GENERIC_READ,0,NULL,OPEN_ALWAYS,FILE_ATTRIBUTE_NORMAL,NULL);
  for(lCount=0;lCount<5;lCount++)
  {
  fp=lCount*lSize;
  ReadFile(hFile,&cmThing[lCount],lSize,&fp,NULL);
  }
  CloseHandle(hFile);
}

void DisplayData()
{
  char cL1[20], cL2[20], cL3[20], cCount[20];
  char cRL[20], cRT[20], cRR[20], cRB[20];
  char cSep[5]=" - ";
  RECT rcTest;
  for(lCount=0;lCount<5;lCount++)
  {
    char cCat[10]="My Thing";
    _ltoa(cmThing[lCount].Getl1(),cL1,10);
    _ltoa(cmThing[lCount].Getl2(),cL2,10);
    _ltoa(cmThing[lCount].Getl3(),cL3,10);
   CopyRect(&rcTest,cmThing[lCount].GetRC());
   _ltoa(rcTest.left,cRL,10);
   _ltoa(rcTest.top,cRT,10);
   _ltoa(rcTest.right,cRR,10);
   _ltoa(rcTest.bottom,cRB,10);
   _ltoa(lCount,cCount,10);
   strcat(cCat," = ");
   strcat(cCat,cCount);
   strcat(cCat,"\n");
   strcat(cCat,"Longs:");
   strcat(cCat,"\n");
   strcat(cCat,cL1);
   strcat(cCat,"\n");
   strcat(cCat,cL2);
   strcat(cCat,"\n");
   strcat(cCat,cL3);
   strcat(cCat,"\n");
   strcat(cCat,"RECTs");
   strcat(cCat,"\n");
   strcat(cCat,cRL);
   strcat(cCat,"\n");
   strcat(cCat,cRT);
   strcat(cCat,"\n");
   strcat(cCat,cRR);
   strcat(cCat,"\n");
   strcat(cCat,cRB);
   MessageBox(NULL,cCat,"Debug",NULL);
  }
}

Everything works fine until I run DisplayData(). It goes through the for loop fine until it get to (lCount==4) and then I get an invalid page fault error.

This doesn't happen if I don't populate the variables with either FillData() or ReadData(). It runs fine and just gives me a MessageBox with a bunch of 0's for my values.

My mistake is most likely then in my FillData() function, but I just don't see it.