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Message-ID: <20260130173517.GC3520958@port70.net>
Date: Fri, 30 Jan 2026 18:35:17 +0100
From: Szabolcs Nagy <nsz@...t70.net>
To: Eleanor Bartle <eleanor@...anor-nb.com>
Cc: musl@...ts.openwall.com
Subject: Re: New C Qualifier Idea
* Eleanor Bartle <eleanor@...anor-nb.com> [2026-01-30 20:55:31 +1100]:
> Hello. I had an idea for a new C type qualifier for a future standard, but don’t know where to share it for feedback. Apologies if this is the wrong place.
>
sc22wg14 @ open-std.org is the discussion list of the standard.
you will likey need to implement it in a compiler, so gcc or
clang issue tracker can be another place to start if you have
compelling reasons why others should look into it.
a libc list cannot help much.
the proposal below is not detailed enough, does not use standard
terms and not clear what it tries to achieve at what cost.
> The qualifier is 'confine', and it would work as follows:
>
> confine char *postfix (confine char *str, uintptr_t from) {
> // ERROR: shared outside function
> // global_var = str;
>
> // OK: returned to caller
> return *str[from];
> }
>
> // ...
> char *post = postfix(str, 10);
>
> // ERROR: returned from function
> return post;
>
> The 'confine' qualifier annotates pointers to stack-allocated values in higher scopes. it would prevent these values from being shared outside the function, but not from being returned from the function; a returned 'confine' pointer behaves as a pointer to local in the calling scope, i.e. returning or saving it becomes a detectable error.
>
> Ideally the sense would be inverted, i.e. there would be a 'permit' qualifier that denotes the opposite meaning and no qualifier would mean 'confine', but that horse has long since bolted.
>
> Prior art is D's 'scope' and 'return scope' qualifiers, and Zig once entertained the idea under the name 'nocopy'.
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