Hidden members of Class objects

Mar 06, 2024

Carl Sturtivant

Mar 06, 2024

H. S. Teoh

Mar 07, 2024

Carl Sturtivant

Mar 07, 2024

kinke

Mar 07, 2024

Richard (Rikki) Andrew Cattermole

Mar 07, 2024

Mar 26, 2024

Carl Sturtivant

On Wed, Mar 06, 2024 at 11:39:13PM +0000, Carl Sturtivant via Digitalmars-d-learn wrote: > I notice that a class with no data members has a size of two words (at 64 bits). Presumably there's a pointer to a table of virtual functions, and one more. Is the Vtable first? [...] > What is actually in these objects using that space? In D, there's a pointer to the vtable and another pointer to a Monitor object (used for synchronized methods). There was talk about getting rid of the Monitor field years ago, but nothing has happened yet. T -- MAS = Mana Ada Sistem?

On Wednesday, 6 March 2024 at 23:45:00 UTC, H. S. Teoh wrote: > In D, there's a pointer to the vtable and another pointer to a Monitor object (used for synchronized methods). There was talk about getting rid of the Monitor field years ago, but nothing has happened yet. Very interesting: is the monitor field ever touched by compiled D code at any point nowadays? Or is it just vestigial?

On Thursday, 7 March 2024 at 00:28:17 UTC, Carl Sturtivant wrote:

On Wednesday, 6 March 2024 at 23:45:00 UTC, H. S. Teoh wrote:

In D, there's a pointer to the vtable and another pointer to a Monitor object (used for synchronized methods). There was talk about getting rid of the Monitor field years ago, but nothing has happened yet.

Very interesting: is the monitor field ever touched by compiled D code at any point nowadays? Or is it just vestigial?

It's (lazily initialized and) used by the synchronized(<expression>) statement (§3 of https://dlang.org/spec/statement.html#synchronized-statement) and the mentioned synchronized class methods (https://dlang.org/spec/class.html#synchronized-methods).

On 07/03/2024 1:28 PM, Carl Sturtivant wrote: > On Wednesday, 6 March 2024 at 23:45:00 UTC, H. S. Teoh wrote: >> In D, there's a pointer to the vtable and another pointer to a Monitor object (used for synchronized methods). There was talk about getting rid of the Monitor field years ago, but nothing has happened yet. > > Very interesting: is the monitor field ever touched by compiled D code at any point nowadays? Or is it just vestigial? Yes its opt-in. https://dlang.org/spec/statement.html#synchronized-statement

March 07, 2024

Re: Hidden members of Class objects

Posted by cc
in reply to Richard (Rikki) Andrew Cattermole

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Posted in reply to Richard (Rikki) Andrew Cattermole

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On Thursday, 7 March 2024 at 00:38:30 UTC, Richard (Rikki) Andrew Cattermole wrote:

On 07/03/2024 1:28 PM, Carl Sturtivant wrote:

On Wednesday, 6 March 2024 at 23:45:00 UTC, H. S. Teoh wrote:

Very interesting: is the monitor field ever touched by compiled D code at any point nowadays? Or is it just vestigial?

Yes its opt-in. https://dlang.org/spec/statement.html#synchronized-statement

I've stumbled over the Monitor/etc sometimes writing serialization, RPC, LUA etc modules iterating over class members, looking for UDAs, after trying to separate everything out using isFunction/isTemplate/etc, on top of dealing with overload spaghetti, I now just explicitly do something dumb like this to get those edge cases out of the way:

static foreach (sym; __traits(allMembers, T))
static if (!["__ctor","__dtor","__xdtor","Monitor","factory"].canFind(sym)) {{
	...

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