On 1/29/16 9:35 PM, Matt Elkins wrote:
On Saturday, 30 January 2016 at 02:09:55 UTC, Steven Schveighoffer wrote:
I figured out a way to have them. You just have to guarantee you don't
copy the actual "pointer" out of the struct:
https://forum.dlang.org/post/mk5k4l$s5r$1...@digitalmars.com
Unfortunately, that won't work for what I was trying to do. The stuff I
elided in the comments were more pointers to other Foo instances, used
to create a linked-list (of stack-allocated objects); these would still
break under the conditions Ali described. I was only storing the this
pointer so that blitted objects could deduce where they came from
(trying to turn the post-blit constructor into a copy-constructor).
Ah, so you were actually counting on the postblit to have an *invalid*
pointer to begin with :) Yeah, that isn't going to work. In D, it's
legal to do something like memcpy struct data (with no postblit), and
this is done quite often in many places because of that.
Thanks, though. I'm thinking that maybe D just can't express these
semantics without substantial overhead. While somewhat disappointing (I
came into D with stars in my eyes :)), it's not enough by itself to make
me go back to C++, at least not just yet. Not when I can just use a few
static ifs to do what previously required careful template crafting that
I wouldn't understand 3 months later. On the other hand, I'm falling
behind on my library books since I no longer have any time for reading
during compilations ;).
There are some really smart people who frequent these forums, if you
post your actual use case, you may get an answer that you hadn't thought of.
I saw you were trying to implement something like std::unique_ptr? There
is http://dlang.org/phobos/std_typecons.html#.Unique
Not sure if it helps.
-Steve
