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Re: [std-proposals] Fwd: Extension to runtime polymorphism proposed

From: Thiago Macieira <thiago_at_[hidden]>
Date: Wed, 08 Apr 2026 09:27:36 -0700
On Wednesday, 8 April 2026 03:36:01 Pacific Daylight Time Muneem via Std-
Proposals wrote:
> I will email an extensive document describing how everything's assembly
> code will look like

Assembly isn't important at this stage. We need only the abstract machine and
the language syntactic rules. You may use assembly to justify why the changes
to the abstract machine and syntax must be done, but mind you that they are a
weak justification because a sufficiently smart compiler could achieve them too.

> 2. xvalues!? like I dont get it, like isn't an xvalue overloaded using T&&,
> so the rules in point 1 should apply.

Since C++11, we have had not 2, but 5 value categories:

rvalue
lvalue
xvalue
glvalue
prvalue

xvalues can "decay" into a glvalue or an rvalue. So, what are the rules for
your new value category? Take a look at N3055 to see how it was proposed. See
[basic.lval] for the current text. See [conv.lval] to see one of the
conversion rules where you must insert yourself.

-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
  Principal Engineer - Intel Data Center - Platform & Sys. Eng.

Received on 2026-04-08 16:27:43