There was a recent thread on this
https://lists.isocpp.org/std-proposals/2024/11/11585.php

Cheers,
Jeremy

On Wed, Dec 18, 2024 at 04:50 Jan Schultke via Std-Proposals <
std-proposals_at_[hidden]> wrote:

> I want to have break/continue statements with labels in C++. Now is the
> time.
>
> https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3355.htm has been
> accepted into C2y, with the syntax:
>
> label: for (/* ... */) {
> while (true) { break label; }
> }
>
> https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3377.pdf proposes to
> update this syntax to
>
> for label (/* ... */) {
> while (true) { break label; }
> }
>
> While N3377 may be a bit more syntactically sound (not reusing labels
> that are otherwise only goto targets, I'm not a fan of that idea.
> Putting "label:" before a loop has a lot of precedent in other
> languages (e.g. Java). Assuming that N3377 gets rejected, the syntax
> would also be a good fit for C++.
>
> There is no good solution for breaking out of nested loops, or out of
> a switch statement within a loop:
> - You can put the whole thing into a function and rely on "return",
> but that may decrease readability and add the cost of a whole new
> separate function.
> - You can use an IILE (immediately invoked lambda expression), but
> that increases indentation level, makes a new scope, and overall adds
> unwarranted complexity.
> - You can use "goto after_loop;" with some label, but goto does not
> work in constant expressions, is unconditionally banned from some
> style guides, and overall won't be the future.
> - You can use an extra bool to indicate whether the outer loop should
> continue, but this adds more mutable state to your function and
> doesn't express the idea of "just break out of both loops" clearly.
>
> Every alternative sucks, and most general purpose languages provide
> some way of breaking out of multiple loops. C++ is really behind and
> should follow in C's footsteps, with whatever syntax C2y lands on.
>
> Note that "break label" has been proposed most recently in
> https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n3879.pdf
> (was rejected), but this is because the author stupidly bunched the
> popular "break label" idea together with unpopular, novel ideas, such
> as "goto case-label" within switches, and the whole thing was thrown
> out.
>
> Since then, IIRC there have also been other proposals like "break N"
> for breaking out of N nested loops, but all of those were rejected.
>
> Anyhow, my questions for std-proposal are mainly:
> - Is anyone already working on this?
> - Is anyone interested in co-authoring?
>
> I have no doubt in my mind that a small, simple, proposal which just
> brings the syntax from C2y into C++ will pass, and we might even make
> it into C++26 if we act swiftly.
>
>
> Yours
> Jan Schultke
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