Hi,
In response to the faq question
Why does the test ExceptionTest.testAssignment failed in CppUnit test
suite?
I don't know if anyone has responded to this bug yet but here is what I
discovered.
As best as I can tell when cppunit Excepiton::operator= calls
SuperClass::operator= (which really is std::exception::operator=), the
cppunit Exception object's vtable address is overwritten with that of
std::exception's vtable address. So when you call the what() method (a
call through the vtable since it is virtual), instead of calling cppunit
Exception's what(), it calls std::exception's what. This returns the
value stored in std::exception's _m_what member, which is "Unknown
exception" (the default value). So either there is a bug in
std::exception operator= or the compiler is not properly setting up the
vtable when calling std::exception operator=. The copy constructor works
fine.
You can fix the bug by either
- Don't have cppunit's class Exception inherit from std::exception and
remove all use of std::exception.
NOTE: I tried this and it worked fine. I.e. ExceptionTest.testAssignment
passed. Not really sure why you are inheriting from std::exception since
nothing in it is really used.
or
- Still have cppunit's class Exception inherit from std::exception and
use it's _m_what member instead of cppunit Exception's m_message. You
need to make these changes
* add std::exception initialization to the following cppunit Exception
constructor
Exception::Exception( std::string message,
long lineNumber,
std::string fileName ) :
std::exception ( message.c_str() ), <=== add this to initialize
std::exception's _m_what member
// m_message( message ), <== remove this not needed any more. using
std::exception to hold the message
m_lineNumber( lineNumber ),
m_fileName( fileName )
{
}
* remove m_message and all it's uses
* remove the what() method from exception.h and it's implementation from
exception.cpp. You can still call what() as it will invoke
std::exception::what() which will return the value in _m_what as a const
char *.
NOTE: I tried this and it worked fine. I.e. ExceptionTest.testAssignment
passed. However, the problem with this is that the vtable address for
cppunit Exception is wrong if operator= is ever called. Could lead to
problems down the road.
or
- Leave everything as is and get MS to fix their bug.
~greg
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