Leandro Lucarella wrote:
Andrei Alexandrescu, el 7 de octubre a las 14:16 me escribiste:
Sean Kelly wrote:
== Quote from Andrei Alexandrescu (seewebsiteforem...@erdani.org)'s article
dsimcha wrote:
== Quote from Andrei Alexandrescu (seewebsiteforem...@erdani.org)'s article
It is a bad idea because distinguishing between release of (expensive)
resources from dangerous memory recycling is the correct way to obtain
deterministic resource management within the confines of safety.
This is based on two faulty assumptions:
1. Memory is cheap. (Not if you are working with absurd amounts of data).
2. Garbage collection is never a major bottleneck. (Sometimes it's a
worthwhile
tradeoff to add a few manual delete statements to code and sacrifice some safety
for making the GC run less often.)
malloc.
So for placement construction of a class, I guess it would look something like:
auto x = cast(MyClass) malloc(MyClass.classinfo.init.length);
x.__ctor( a, b, c ); // construct
...
x.__dtor();
free( cast(void*) x );
Is that right?
Yes, I think so, but I haven't checked all the details. For example
I'm not sure whether __ctor copies .init over the memory before
running the user-defined constructor, or expects that to have been
done already.
My understanding from Walter is that __ctor(x, y, z) are simply the
functions this(x, y, z) as written by the user, so you'd need to
memcpy the .init by hand before calling __ctor.
What I don't understand is why you're willing to make that hard to do
manual memory management in D. Do you see that you're making the
programmer's job deliberately for no reason? D needs conservative GC,
which means slow GC; by definition. D is a system programming language, so
it's expected to be fast, but because of the GC there will be often
situations where you have to do manual MM. Why are you making that much
harder?
You know that in the search for safety you'll be making much more unsafe
(or bug-prone) to do manual MM?
You seem to be asserting that without additional built-in language
support, manual memory management is unduly difficult. Why so?
Andrei
