[comp.lang.c++] C++ 2.0 on HPollo DN10000

rihaczek@jellosub.luftfahrt.uni-stuttgart.de (Clemens Rihaczek) (05/16/91)

Hi, there!

Sorry, I've only recently started programming in C++, so this might 
be a stupid question.  Anyway, here is an attempt to describe my problem:

Say, there are two classes, one called Object (just some plain-vanilla
class) and one called ObjectArray (hosting an array of pointers to instances
of class Object).  This is what they might look like:

class Object
	{
	inline double& ObjVal() { return obj_val; }
	...
	double obj_val;	
	}

class ObjectArray
	{
	inline Object*& operator[](unsigned int index) { return elements[index]; }
	...
	Object* * elements;
	}

Now, when I use the following piece of code on an Apollo DN10000,  

	ObjectArray oa(...);
	oa[i]->ObjVal() = ....;

oa[i]'s obj_val member turns out to have some crud value like 2.277e-308
(smallest double?). Turning off the optimizer helps a little, the values
become slightly 'more reasonable', but, hey -- junk is junk.

Introducing a dummy variable op (an Object pointer)

	ObjectArray oa(...);
	Object* op;
	op = oa[i];
	op->ObjVal() = ....;

solves the problem and the contents of the obj_val member reads ok.

Both versions work fine on an Apollo DN3500.

 *** WHY? ***

Please excuse my ignorance, conserve energy (no flames...)


-- 

Clemens Rihaczek                   ISD (Department for Statics and 
                                   Dynamics of Aerospace Structures)
                                   University of Stuttgart 
                                   Pfaffenwaldring 27
fax:      +49 711-685-3706         7000 Stuttgart 80, West Germany.
voice:    +49 711-685-3899
Internet: rihaczek@dogmatix.luftfahrt.uni-stuttgart.de (129.69.110.10)