Re: C++ rtti hack

bji-ggcpp@ischo.com wrote:
::
:: And, is there value in C++ leaving the door open for such compilers
:: to exist, rather than specifying more stringent rules on how classes
:: have to be laid out, including where the vtable and rtti data for a
:: class is?

Is there a great value of closing the door for such compilers?

::
:: On the contrary ... do you think it's valuable to be able to write
:: code that simply takes a pointer to "an object" of unknown type, and
:: is able to detect the type of that object? I think it is.

I don't. :-)

For polymorphic types it might be, but can most often be solved by using
virtual functions.

For pointers to non-polymorhpic objects, you program shouled be able to
track the pointer better than "I have a pointer to some object".

:: I think
:: it's *much* more useful than allowing compilers to play silly games
:: which I highly, highly doubt any compiler writer has ever been
:: sadistic (or is it masochistic?) enough to implement in practice.

The idea with C++ is that you should not give up performance for silly
features that you don't use. The more restrictions you add to the
details of
the required implementation, the less room you leave for smart compilers.

It is possible to have a C++ implementation on machines with 9 bit
bytes, 36
bit integers, using ones complement, and 72 bit floating point. You don't
have to have a hardware stack, and vtables are not required.

C++ is this way, not by mistake but by design. If you want it the other way
round, you could go with Java.

Bo Persson

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