[Cppunit-devel] cppunit FAQ 2.3: Why does the test ExceptionTest.testAssignment f ailed in CppUnit test

[Maxwell, J. (M. GEMS-IT) <Joh...@me...>]

Gentlefolk:

Dunno if this is a frequently answered question, but I've tracked
it down, so I thought I'd post, just in case it isn't old news:

Short form:
    The test fails because assignment of CppUnit::Exception objects
is broken.

Long form:
    In CppUnit::Exception::operator=, there's a call to
SuperClass::operator=(). Under VC++, that doesn't do anything useful,
and it *does* change the type of the object to the SuperClass. That is,
after the SuperClass::operator= call this's vtable pointer now points to
the vtable for exception, instead of the vtable for CppUnit::Exception.
So the assignment operator is broken, and the test correctly detects it
and complains.

The more interesting question, and I'm not language lawyer enough to
answer it definitively, is whether VC++'s exception class's behavior is
broken or not. I'd tend to say yes, just based on general anti-MS
prejudice,
but on the other hand, IIRC, that library was produced by PJ Plauger's
Dinkum Software... and I have a fair degree of respect for that man

I haven't devoted much effort to researching the correct answer, but a
#ifdef _MSC_VER / #endif pair wrapped around that call to
SuperClass::operator=() provides symptomic relief of pain.

cc me on replies if you want me to see them; I don't subscribe to this
list.
Use either Joh...@me... (work) or jm...@to... (home).

-John.
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