Re: Cast to void * and back.
On May 6, 8:03 am, jasonc <jason.cipri...@gmail.com> wrote:
On May 3, 12:55 pm, James Kanze <james.ka...@gmail.com> wrote:
On May 3, 4:55 pm, "Alf P. Steinbach" <al...@start.no> wrote:
* Juha Nieminen:
Alf P. Steinbach wrote:
E.g. a 'void (*)()' can not be cast to 'void*' in standard
C++, because in standard C++ code and data live in two
logically separate address spaces.
Wouldn't that only be relevant if you are *comparing*
pointers (because if function pointers and data pointers use
their independent address spaces, then comparing the value
of a function pointer to the value of a data pointer might
give you that they are equal, even though they really
aren't; they are equal in value, but are pointing to
completely different locations)?
No, it's very strict: function pointers and data
pointers are two different kinds of beasts, and in
standard C++ never shall the two twains intermingle.
This will change in C++0x. Conditionally:-).
I'm not sure what "conditionally supported" means in
C++0x. I think it's basically an "implementation
defined" in which one of the allowed possibilities is an
error from the compiler. (And if there isn't a
diagnostic, the code is required to work.)
... really? Am I misunderstanding what you are saying
about C++0x, or does this seem like a portability
nightmare waiting to happen?
I'd say that it's a portability nightmare which has already
happened. I regularly have to modify my sources when I
encounter a new implementation of the library, because I've
forgotten to include a header for something I needed, but it
was included indirectly from another header.
(In this respect, I try to compile all my code using Sun CC
with the STLPort. The quality of the library itself is so
bad you really can't use it in production code, but it does
seem to indirectly include a lot less than any of the other
implementations I've used.)
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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