Fixing a memory leak

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6 total messages Started by Terry Fri, 11 Apr 2003 17:41

#17058

Author: Terry
Date: Fri, 11 Apr 2003 17:41

60 lines
2419 bytes

I have a function that i am calling like this

    int FileSize;
    PeopleType *People = (PeopleType*)ReadFileToBuffer("Database.dat",
&FileSize);

//--------------------------------------------------------------------
-------
char* TForm1::ReadFileToBuffer(char *FileName, int *FileSize)
//
// Returns:
//  CharPointerToData if Successful
//  NULL if Failed
{
 HANDLE FileHandle = CreateFile(FileName, GENERIC_READ,
FILE_SHARE_READ,
                          NULL, OPEN_EXISTING,

FILE_ATTRIBUTE_NORMAL|FILE_FLAG_SEQUENTIAL_SCAN,
                          NULL);

 if(FileHandle == INVALID_HANDLE_VALUE || FileHandle == NULL) return
NULL;

 *FileSize = (int)GetFileSize( FileHandle, NULL );

 if( *FileSize == 0xFFFFFFFF )
 {
  CloseHandle( FileHandle );
  return NULL;
 }

 char* pBuffer = new char[*FileSize];

 DWORD NumberOfBytesRead;

 if(ReadFile(FileHandle, (void*)pBuffer, (DWORD)*FileSize,
&NumberOfBytesRead, NULL) == 0)
 {
  CloseHandle( FileHandle );
  delete[] pBuffer;
  return NULL;
 }

 CloseHandle( FileHandle );
 return pBuffer;
}
//--------------------------------------------------------------------
-------

The problem is when i create the pBuffer here, i get a resource leak
because i am
not deleting the pBuffer.  Can someone give me some advice on how to
delete this
so i don't get a memory leak.  I tried deleting in the form
OnDestroy(), but that
does no good.


Thanks.

Re: Fixing a memory leak

#17059

Author: JD
Date: Fri, 11 Apr 2003 17:50

13 lines
1124 bytes

Try this:

    PeopleType *People = (PeopleType*) ReadFileToBuffer "Database.dat", &FileSize);
    if( People )
      {
      // use People;
      delete People;
      }

BTW: It is permissable to delete a NULL pointer in C++

~ JD

Re: Fixing a memory leak

#17061

Author: Remy Lebeau (TeamB)
Date: Fri, 11 Apr 2003 19:35

26 lines
1525 bytes

"JD" <nospam@nospam.com> wrote in message
news:3e970049$1@newsgroups.borland.com...

> Try this:
<snip>

That is not valid.  The memory was allocated as a char[] but then you're
freeing it as a People* instead.  They must match.  So the memory has to be
freed as a char* using delete[] instead:

    char *pBuf = ReadFileToBuffer("Database.dat", &FileSize);
    if( pBuf )
    {
        PeopleType *People = (PeopleType*)pBuf;
        // use People as needed

        delete[] pBuf;
    }

> BTW: It is permissable to delete a NULL pointer in C++

Yes.


Gambit

Re: Fixing a memory leak

#17062

Author: Terry
Date: Fri, 11 Apr 2003 20:15

20 lines
1424 bytes

Thanks JD, let me give it a shot.


"JD" <nospam@nospam.com> wrote in message
news:3e970049$1@newsgroups.borland.com...
>
> Try this:
>
>     PeopleType *People = (PeopleType*) ReadFileToBuffer
"Database.dat", &FileSize);
>     if( People )
>       {
>       // use People;
>       delete People;
>       }
>
> BTW: It is permissable to delete a NULL pointer in C++
>
> ~ JD
>

Re: Fixing a memory leak

#17064

Author: Terry
Date: Fri, 11 Apr 2003 23:24

22 lines
1635 bytes

Great, thanks a lot, no more codeguard errors.

"Remy Lebeau (TeamB)" <gambit47@yahoo.com> wrote in message
news:3e971900$1@newsgroups.borland.com...
>
> > Try this:
> <snip>
>
> That is not valid.  The memory was allocated as a char[] but then
you're
> freeing it as a People* instead.  They must match.  So the memory
has to be
> freed as a char* using delete[] instead:
>
>     char *pBuf = ReadFileToBuffer("Database.dat", &FileSize);
>     if( pBuf )
>     {
>         PeopleType *People = (PeopleType*)pBuf;
>         // use People as needed
>
>         delete[] pBuf;
>     }

Re: Fixing a memory leak

#17068

Author: JD
Date: Sat, 12 Apr 2003 01:30

18 lines
1300 bytes

"Remy Lebeau \(TeamB\)" <gambit47@yahoo.com> wrote:
>
>"JD" <nospam@nospam.com> wrote in message
>news:3e970049$1@newsgroups.borland.com...
>
>> Try this:
><snip>
>
> That is not valid.  The memory was allocated as a char[] but
> then you're freeing it as a People* instead.


>        They must match.

I did not know that (obviousely)

~ JD

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