[omniORB] Allocation of memory for sequence "vars"

[Visscher, Bruce]

> I have a very simple sequence that I am allocating and would like to
> check that the allocation was successful.
> 
> The IDL is :
> 
>     interface SEQ {
>     
>         enum ABC { want, more };
>         typedef sequence<ABC> ABCseq;
>     };
> 
> And the code (C++) I wish to convert is:
>  
>    SEQ::ABCseq_var me = new SEQ::ABCseq();
>     if(me == NULL) printf("ERROR\n");

This is actually wrong for 2.5 reasons. :-)

The main reason is that standard C++ will never set the null pointer to 0, but 
will instead throw an exception (std::bad_alloc, IIRC...In any case it should
be derived from std::exception so you can catch(std::exception&)).  So, the
printf should never execute anyway (some compilers might have a backwards
compatibility flag to cause new to return 0 instead).

The other reason is that the var type would be initialized to nil, not 0. So,
to check whether an object has been allocated you should use CORBA::is_nil(me)
instead.

The 0.5 reason is that the null pointer is spelled "0" in C++, not "NULL".

> 
> When I compile this, using OMNI, I get an error on the "me == 
> NULL" test
> to the effect that no such comparison is available.

....which is a good thing since this isn't correct code.

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