On Sunday, 12 June 2016 at 14:49:18 UTC, Gary Willoughby wrote:
Hmmm. I thought it looked *too* simple. Have you any idea if
there is a simple solution to this?
yes. you have to turn your refcount to pointer. ;-)
the cause of "misbehave" is the fact that there can exist several
copies of the struct made in different program points, and they
all have *independent* refcounter. but all those copies should
have the *same* refcounter. the easiest way to solve this is to
allocate refcounter separately, and only share *pointer* to it,
like this:
struct Foo {
int* refcount;
void allocResources () {
import core.stdc.stdlib : malloc;
assert(refcount is null);
refcount = cast(int*)malloc(int.size);
*refcount = 1;
// init other resources
}
this (this) { if (refcount !is null) *refcount += 1; }
// we need to do this in opAssign() and in dtor, hence the
function
private void decRef () {
if (refcount !is null) {
if ((*refcount -= 1) == 0) {
import core.stdc.stdlib : free;
free(refcount);
// free resources
}
}
}
~this (this) { decRef(); }
// yes, we need this too
void opAssign (Foo src) {
*src.refcount += 1; // it is important to increase it first,
in case `src` and `this` are sharing refcount
decRef(); // release our resources
*refcount = *src.refcount;
// copy other handles and so on
}
}
this is basically how refcounted structs are done. note that i
just typed the code into reply box, so it may not compile or
contain some small bugs, but i think you got the idea.
