Multiply and Virtual Inheritance for Exceptions

    Are there any problems when using multiply and/or virtual inheritance
for classes used then as exception classes? I often heard that this is
a risky practice however failed to find any strong reasons.

    Also why standard exceptions do not inherit virtually (yes, this fact
suggests answer to the first question)? Usually (or at least in all
nontrivial codes I read or wrote) we have a base exception for the
hole system (application, library or even more general) and then some
few general exceptions (for specific modules - if applicable) and then
appropriate exceptions. Since it is advised to derive any exception
from std::exception (at some level) the most base exception inherits
std::exception. However this virtually disables the use of other
standard exceptions in our hierarchy since this would cause inheriting
from std::exception twice (one from our base exception class and one
from std specific exception class) which generally seems to be wrong
(it makes type casting harder for example). Virtual inheritance would
solve this problem.

    Adam Badura

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