Re: 64b Windows - crashes not detected

From:

phil oakleaf <news@oakleafsoftware.co.uk>

Newsgroups:

microsoft.public.vc.mfc

Date:

Thu, 20 Aug 2009 17:17:52 +0100

Message-ID:

<uubXZHbIKHA.3860@TK2MSFTNGP05.phx.gbl>

Goran wrote:

On Aug 20, 3:16 pm, phil oakleaf <n...@oakleafsoftware.co.uk> wrote:

If I have a program that compiles but crashes on 32bit but fails to
crash on 64bit then I would start by thinking it is connected (somehow)
to 64bit.

With what right do you expect any consistency when invoking undefined
behavior, such accessing bad pointers? That's your primary mistake. If
you don't understand, or fail to accept the simple truth of undefined
behavior, as defined by C and C++ programming languages, potential
difference between 64 and 32-bit environment is the least of your
problems.

(I, too have 64-bit system and work on my 32-bit code in it. It's been
~2 years now. __Not once__ did I notice a difference from a 32-bit
system WRT memory access, and I, too, produce my fair share of bugs. I
believe you are acting under hugely false presumptions.)

On Aug 20, 3:16 pm, phil oakleaf <n...@oakleafsoftware.co.uk> wrote:

Developing on a 32bit platform 99.9% of bad-pointer problems trigger the
debugger, I dont regard this as relying on luck but using the tool as an
assistant.

Well, you indeed have some cheek! You are relying on undefined
behavior (trying to, rather). How can this be called "using a tool" is
beyond me. ( And I know that 67.43% of all stats are made up on the
spot, so I doubt your 99.9 figure :-). )

Step up to the plate and provide a repro of a difference - same code
crashing under 32 and running (seemingly fine) under 64. Here's an
offer: if you do that, I'll take time to try to explain what happened.
There is no mystery in this (or any engineering) field, only our
inability to understand it.

Goran.

create a standard MFC app from scratch and add the code below

- on the 64bit machine this compiles and runs straight past the
NULL->testMe() part

- on the 32bit machine - Unhandled exception which is what I would expect

I am running VS-2005 on Windows 7 64bit

What does this code do on your 64bit machine

Look forward to hearing what happens on your system
Phil

// couple of very simple classes

class MTest
{
public:
    float m_aVal;
    float m_bVal;
    MTest():m_aVal(0),m_bVal(0) {}

};

class RoomTest
{
public:
    MTest *m_mat;

    RoomTest():m_mat(NULL) {}

    virtual MTest *getMaterial() {return m_mat;}

    virtual void testMe()
    {
        MTest *tt=getMaterial();
        tt->m_bVal=45;
        tt->m_aVal=46;
    }
};

void CcrashTestView::OnDraw(CDC* /*pDC*/)
{
    CcrashTestDoc* pDoc = GetDocument();
    ASSERT_VALID(pDoc);
    if (!pDoc)
        return;

    // just create a real one
    RoomTest testRoom;

    // NULL pointer
    RoomTest *room=NULL;

    // call testMe on the NULL Pointer
    room->testMe();

    // TODO: add draw code for native data here
}