Am 17.03.2013 16:20, schrieb Jakob Ovrum:
On Saturday, 16 March 2013 at 14:40:58 UTC, D-ratiseur wrote:
new is overriden in TUObject because the purpose of the library is to
bypass the garbage collector and to bypass the GC you have to
override new and delete.(at least according to the manual:
articles,mem managment).
The documentation on this is old and misleading.
Overloading of new and delete is deprecated (the delete operator in its
entirety is deprecated).
Having them overloadable was not a very good idea. The current approach
is to have "new" always mean GC memory, which is why there is no need
for delete. This way, code that uses 'new' won't break horribly or leak
depending on the type involved, important for generic code. Code that
doesn't use the GC has to be designed for it; you can't just remove the
GC under everyone's noses and expect things to work.
For different kinds of memory, you should simply use a different
allocator. For example, here's a rough approximation of a pair of
functions using malloc/free for class allocation:
T alloc(T)() if(is(T == class))
{
enum size = __traits(classInstanceSize, T);
auto p = enforceEx!OutOfMemoryError(malloc(size));
return emplace!T(p[0 .. size]);
}
void dealloc(T)(ref T obj) if(is(T == class))
{
free(cast(void*)obj);
obj = null;
}
It can easily be overloaded to support all types.
In the future, Phobos will have a custom memory allocator library, which
modules like std.container will use, though to which extent is not clear
(for example, will it also use the custom allocator for exception
objects?). Nevertheless it will probably be a good base for other
libraries to easily support non-GC allocators.
You still can't replace evertything with custom alloc templates and have
nice syntax. There are at least two cases where it does not work nicely:
1) Arrays (no new T [size] syntax)
2) Inner classes (a template can't automatically capture the outer class)
So I think overloading new and delete actually has its place. But the
way it is currently implemented in D is useless in my eyes.
Kind Regards
Benjamin Thaut
