Cannot get the offset of static members of a struct
struct X
{
__gshared public:
int x;
}
X.x.offsetof < invalid.
We can clearly get a pointer to the static struct X since &X.x is
effectively the address of X(regardless nomenclature and
terminology issues in D trying to hide this).
e.g.,
auto p = cast(X*)&X.x;
will, for all practical purposes be a pointer to X.
auto GetStaticAddress(T)()
{
mixin("auto p = cast(T*)&T."~__traits(allMembers, T)[0]~";");
return p;
}
Of course, assuming that the first member is at the same location
as the start of the struct and the elements are laid out in the
same positions(not sure if this is guaranteed, but probably is).
Would be much nicer if we could just take the address of a static
struct
This is pretty useful for simplification:
auto GetStaticAddress(T)()
{
mixin("auto p = cast(T*)&T."~__traits(allMembers, T)[0]~";");
return p;
}
auto GetOpts(T)(string[] args)
{
import std.getopt, std.meta, std.traits;
auto t = GetStaticAddress!(T)();
string combine()
{
string s = "";
foreach(m; AliasSeq!(__traits(allMembers, T)))
{
mixin("enum a = __traits(getAttributes, T."~m~")[0];");
mixin("s ~= \"`"~a~"`, &"~T.stringof~"."~m~", \";");
}
return s;
}
enum s = combine();
mixin("return getopt(args, "~s~");");
}
struct X
{
align(1):
__gshared public static:
@("A") bool A;
@("B") string B;
@("C") string[] C;
};
which allows us to do
GetOps!X(args)
vs
getop(args, "A", &X.A, "B", &X.B, "C", &X.C);
Could be improved to only deal with special argument attributes
on X's fields and allow for non-static strucs(for the general
case of mapping). Sort of a map between attribute space on a type
and some function.
