--- Comment #8 from jima at cadence dot com 2007-03-21 20:58 ---
I tried using placement-new and explicit destructor calls to
delineate the lifetime of the allocator's internal class objects explicitly,
such that their lifetimes do not overlap with any references to the
same storage vi
--- Comment #7 from jima at cadence dot com 2007-03-21 16:13 ---
(In reply to comment #6)
> ... the proper way is to start a new object lifetime using placement new.
Are you referring only to internal operations in MyHeap::Malloc (in the demo
program), or do you mean that the overall sc
--- Comment #6 from rguenth at gcc dot gnu dot org 2007-03-21 09:58 ---
This is related to PR29286, the C++ aliasing rules are disputedly different
from
the C ones. So at the moment you cannot implement an allocator in C++ (and in
C in general). That said, the proper way is to start a
--- Comment #5 from jima at cadence dot com 2007-03-21 02:31 ---
(In reply to comment #4)
> (In reply to comment #3)
>... Why do you think 1 or 2 more
> instructions will be a hit, most of the problems you are going to hit into now
> is cache issues anyways unless you do a better malloc
--- Comment #4 from pinskia at gcc dot gnu dot org 2007-03-21 01:40 ---
(In reply to comment #3)
> Can you point me to a description of the C++ aliasing rules?
You can find some of it on http://gcc.gnu.org/bugs.html under the non bug
section. There are a lot more pages on then I can
--- Comment #3 from jima at cadence dot com 2007-03-21 01:32 ---
Can you point me to a description of the C++ aliasing rules?
Is the memcpy() workaround specific to GCC, or is memcpy
part of the standard with special rules regarding aliasing?
(I ask because our code base has to work on
--- Comment #2 from pinskia at gcc dot gnu dot org 2007-03-21 01:14 ---
Note memcpy is the only way to be aliasing safe in this case, oh and make sure
you don't cast the incomming pointer from malloc or from your free.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31289
--- Comment #1 from pinskia at gcc dot gnu dot org 2007-03-21 01:13 ---
This is definitely a C/C++ aliasing violation as you are first accessing it as
a MyHeap::Node and then as derived.
Here is how I would fix it for the first one I would change it to:
void * newnode = malloc(bytes_
