OpenEuphoria

Strange crash

• Posted by Matthew Lewis <matthewwalkerlewis at YAHOO.COM> Sep 12, 2002
• 382 views

I've been having this really strange crash, which I can't explain.  It's in
a function that's used as a callback for an ActiveX control.  It crashes on
this line (machine exception):

rect[3..4] += rect[1..2]

but only in certain places:

function IOleInPlaceSite_GetWindowContext( atom this, atom ppFrame, 
        atom ppDoc, atom lprcPosRect, atom lprcClipRect, atom lpFrameInfo )

    sequence rect
    integer obj_ix
    atom pframe
    
    obj_ix = get_obj_from_this( this )

    if not obj_ix then
        poke4( ppFrame, 0 )
        poke4( ppDoc, 0 )
        poke4( lprcPosRect, repeat(0, 4 ) )
        poke4( lprcClipRect, repeat( 0, 4 ) )
        poke4( lpFrameInfo, repeat( 0, 5 ) )
        -- E_UNEXPECTED
        return #800FFFF
    end if
    
    rect = obj_table[OBJ_POS][obj_ix]

    -- ************************************************
    -- WORKS OK HERE
    rect[3..4] += rect[1..2]
    -- ************************************************

    -- supply the pointer to IOleInPlaceFrame
    pframe = find( IOleInPlaceFrame_b, interface_table[I_BYTES] )
    pframe = interface_table[I_THIS][pframe]
    poke4( ppFrame, pframe )

    -- ************************************************
    -- CRASHES HERE
    --rect[3..4] += rect[1..2]
    -- ************************************************
    
    poke4( lprcPosRect, rect )
    poke4( lprcClipRect, rect )
    
    -- Fill OLEINPLACEFRAME
    poke4( lpFrameInfo, { 20, 0, obj_table[OBJ_PARENT][obj_ix],
                          0, 0 } )
    return 0
end function

I haven't been able to duplicate this elsewhere, but it reminds me of
something where win32lib crashes if you call allocate before creating
controls (at least it did at one point).  Has anyone else ever seen this?
Have any ideas about what's causing it?  Oh, I can also stop the crash by
changing the line to

rect[3] += rect[1]
rect[4] += rect[2]

or printing or somehow referring to rect differently, or simply opening up
the trace window.  It's like it didn't properly allocate space correctly or
something.

Matt Lewis