Justin Johansson wrote:
Jarrett Billingsley Wrote:
On Sat, Oct 3, 2009 at 5:50 PM, Justin Johansson <n...@spam.com> wrote:
How does one determine the sizeof (in bytes) of an instance of a class in D?
.sizeof works as advertised for structs, but for reference types,
.sizeof yields the sizeof the referencing variable (effectively same as size of
a pointer)
and not the size of the underlying instance.
I did try scanning the NG and read spec_D1.00.pdf. Perhaps I missed it in the
latter.
btw. I was poking under the hood of std.xml and though, wow, instances of
Element
class look humongous, and so I'm interested to how exactly how humongous.
There's no way to get it at compile-time in D1. The best you can do is
Class.classinfo.init.length.
In D2, you can use __traits(classInstanceSize, Class).
Thanks Jeremie and Jarrett for answers.
For investigative purposes (rather than adding up class member sizes in my
head),
would I get a fair answer if I copied the class data members into a struct, did
a struct
sizeof and added 4 bytes to allow for a virtual function table pointer (in the
class and
assuming the class has a VFT)?
You forgot the monitor pointer of the class, so thats (size_t.sizeof *
2) to add to the size of the struct.
I wasn't aware of the traits method either, I just made this helper
template to simplify its syntax:
template SizeOf(alias C) if(is(C == class)) {
enum ClassSizeof = __traits(classInstanceSize, C);
}
