Hello Carsten,
after spending some time I have found the problematic code. Actually, I
still do not know what is the real problem but let me explain first.
I have learned that the '.osb' file format involves the following kind of
code:
1. On writing: OSGExceptionBinaryDataHandler.inl, function void
putValue(const Real32& value)
Real32 v = osgHostToNet<Real32>(value);
which melts down to (OSGBaseFunctions.inl)
template <> inline
OSG::Real32 osgSwapBytes<Real32>(OSG::Real32 src)
{
UInt8* pStart = reinterpret_cast<UInt8*>(&src);
UInt8* pEnd = reinterpret_cast<UInt8*>(&src) + sizeof(Real32);
std::reverse(pStart, pEnd);
return src;
}
I could verify that everything is fine to the point of the return call.
However, variable v is not correctly intialized afterwards.
2. On reading the function getValues(Real32* value, UInt32 size) throw
(ReadError) is called in the same source file as above. A similar function
call takes place in this file which is also unsecure (with respect to my
platform):
value[i] = osgNetToHost<Real32>(value[i])
In order to check it more thoroughly, I modified the code in
OSGExceptionBinaryDataHandler in the following way:
Wrpt. to 1)
// Real32 v = osgHostToNet<Real32>(value);
UInt8 buffer[sizeof(Real32)];
memcpy(buffer, reintepret_cast<const void*>(&value), sizeof(Real32));
std::reverse(buffer, buffer+sizeof(Real32));
put(buffer, sizeof(Real32));
Wrpt. 2)
//value[i] = osgNetToHost<Real32>(value[i]);
std::reverse(reinterpret_cast<UInt8*>(&value[i]),
reinterpret_cast<UInt8*>(&value[i])+sizeof(Real32));
With these small modifications, I'm not facing any of the reported problems
anymore.
Unfortunately, I'm not an expert in these matters and can't tell what the
real reason for the problem is. Interestingly, I added the following code
for testing:
Wrpt 1.
if (::boost::math::isnan(v))
__asm int 3;
Wrpt 2.
if (::boost::mathisnan(value[i])
__asm int 3;
These interrupts get be called in the original code. As I have told, I do
not know the exact rules about copying float (doubles) numbers in case of
leaving the valid range of numbers. What I know is that the math coprocessor
is always good for surprises especilly folded by the optimization flags of
the compiler.
So, what to do. I would recommend to go for a little more secure way for the
osgHostToNet and osgNetToHost functions. At least on my platform (win32,
win64) I'm expecting more trouble in this area, so.
What do you think? Gerry, in case you are listening, do you know the
background for this stuff? What is your opinion?
Best,
Johannes
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