The following piece of code runs without error on Windows 4.0 (service
pack 2) and is terminated with a dialog message under 3.51 (service pack
4).

The program calls CopyRect with an uninitilized pointer, which attempts
to read from memory location 0.  I realize that NT 4.0 moved code to
ring zero to enhance performance.  How much did they move?  Will NT 4.0
allow writes to location 0 as well?  Is NT no longer a memory access
protected Operating System?

#include <afxwin.h>
int main ()
{
    RECT    dstRect;
    LPRECT  srcRect;

    srcRect = 0;

    CopyRect (&dstRect, srcRect);

    return 1;

    >>Only by attempting the absurd do we achieve the impossible<<

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Felix,
A couple points to note:
CopyRect arguments go like this: CopyRect (destination, source)
  - all you printfs were stated backwards.

I know all about return codes... It' very difficult to check them when
your application is terminated (NT 3.51) with a "Application Error".
The instruction at "0x?????" referenced memory at "0x0000000". The
memory could not be "read".

So I'll re-ask the original question.  Does NT4.0 check and report
memory access violations?  CopyRect() was just an example.  CopyRect()
was part of an argument to a constructor where it was not possible to
check a return code.  And yes I know about exception handling...

The reason this problem was discovered at all is because we have some
developers coding in 4.0 and others with 3.51.  The code ran without a
hitch under 4.0 and dies a sudden death under 3.51.

        Thanks,  Frank

Frank,

 > So I'll re-ask the original question.  Does NT4.0 check and report
 > memory access violations?  CopyRect() was just an example.

Yes, access violations are checked and reported. CopyRect() was not a
good example because it validates its arguments before trying
anything; that's why I included direct access through a pointer.

If an app works on 4.0 and dies a sudden death under 3.51, my first
suspicion would be that is uses NT4-only functionality or something
like that.

Cheers,
Felix.

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