[ECOS] Multiple Inheritance used in eCos class Cyg_Thread

[Nick Garnett]

Donald Walton <dwalton@dramail.com> writes:

> I would be interested to know the type of testing eCos has been through.
> If it has been successfully tested as part of an embedded aviation
> system, I would agree with you.  If it has been tested as part of the
> embedded system for a printer or digital camera, I would have to
> disagree with you.

eCos has been used is a number of mission critical applications
including automotive and satellite systems. It has certainly been used
in aviation, but probably not in anything safety critical.

> 
> When it comes to developing embedded systems that are safety critical,
> one cannot be too careful.
> 
> If there is little interest in using eCos in safety critical systems,
> leave it as it is.  However, companies and individuals planning to use
> it in areas where safety is important may want to rework the area where
> there is multiple inheritance or plan to accept the cost of extensive
> testing.  In such situations, this can be an additional risk factor for
> a project.

The edict against multiple inheritance is presumably against using it
to develop new application code. In the case of eCos, MI is used only
within the kernel, applications do not have access to the classes
involved, and it is used in a very restricted and controlled
way. There is absolutely no possibility of application code
encountering MI under normal circumstances.

Looking at it a different way: if eCos were a closed source OS,
distributed only as a binary library, then you would not know that MI
were being used internally. The same is true now, even though you can
see the source, the use of MI is not visible.

Very little development now goes on in the kernel, it has been stable
for many years. So the fear that some sort of programming mistake
using MI will introduce a bug is very remote. Changing the kernel to
eliminate MI is much more likely to destabilize it.


-- 
Nick Garnett                                     eCos Kernel Architect
http://www.ecoscentric.com                The eCos and RedBoot experts


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