Re: [PATCH gcc/* 1/2] gcc: copy expected and optional out of rust/utils

Arsen Arsenović <[email protected]> Wed, 19 Aug 2026 14:11:10 +0200

Newsgroups	gmane.comp.gcc.patches,gmane.comp.gcc.rust
Organization	BayLibre
Message-ID	<[email protected]>

[Cleaned up CC; added Jonathan and libstdc++@ to CC]

Jakub Jelinek <[email protected]> writes:

> Please put it into gcc/ directly then.
> I really dislike other subdirs with extremely few files, it is significant
> inbalance having directories for almost nothing vs. the 1000+ files
> directory, e.g. the gcc/topics/ directory containing a single header, or
> gcc/custom-sarif-properties/ which has 6 files in it or
> gcc/sym-exec/ with 7 files in it.  All those would be better in gcc/
> directly, custom-sarif-properties with some file prefixes, sym-exec as is.

Sure, that's OK with me, but note that Jason suggested giving them their
own directory because they're pulled in from elsewhere
(https://github.com/TartanLlama/expected and
https://github.com/TartanLlama/optional, which place them in 'tl/'; we
could also place a copy of the CC0 in there).

Of course, that's an obsolete consideration if we reuse the libstdc++
implementation.

> And yes, I'd think we should based it on libstdc++ implemenntation
> rather than some third party (sure, some tweaks will be needed, we
> need to work with any C++14 implementation, so stop relying on stuff
> from <bits/c++config>).
>
> Also, I'd say we should use <expected>/<optional> directly when being
> compiled with C++23 resp. C++17, only use the extra headers as
> fallback for older C++ compilation, so that when we eventually bump
> minimum C++ version to C++17 (or much later to C++23), we can remove
> those headers.

Yes, I agree.

Jonathan, what do you think about reusing <optional> and <expected> in
gcc/?  (with the goal of eventually removing them)

That'd mean they need to be modified to work with any C++14 compiler.

Given that this is temporary, I imagine just maintaining the two
implementations separately might be okay, but I also imagine that the
temporary period will be of ~10 years for <expected> at least.

I think that the Rust FE should be able to switch to using the libstdc++
implementation quite easily, too, since the current implementation is
meant to be compatible with the standard one.
-- 
Arsen Arsenović

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