Re: [GSoC] gccrs Unicode support

[Thomas Schwinge <thomas@codesourcery.com>]

Hi!

(By the way, this GSoC project is being discussed in GCC/Rust Zulip:
<https://gcc-rust.zulipchat.com/#narrow/stream/327528-GSoC/topic/Unicode.20support>.)

I'm now also putting Mark Wielaard in CC; he once also started discussing
this topic, "thinking of importing a couple of gnulib modules to help
with UTF-8 processing [unless] other gcc frontends handle [these things]
already in a way that might be reusable".  See the thread starting at
<https://inbox.sourceware.org/gcc/YPQrMBHyu3wRpT5o@wildebeest.org>
"rust frontend and UTF-8/unicode processing/properties".

On 2023-03-15T16:18:18+0100, Jakub Jelinek via Gcc <gcc@gcc.gnu.org> wrote:
> On Wed, Mar 15, 2023 at 11:00:19AM +0000, Philip Herron via Gcc wrote:
>> Excellent work on getting up to speed on the rust front-end. From my
>> perspective I am interested to see what the wider GCC community thinks
>> about using https://www.gnu.org/software/libunistring/ library within GCC
>> instead of rolling our own, this means it will be another dependency on GCC.
>>
>> The other option is there is already code in the other front-ends to do
>> this so in the worst case it should be possible to extract something out of
>> them and possibly make this a shared piece of functionality which we can
>> mentor you through.
>
> I don't know what exactly Rust FE needs in this area, but e.g. libcpp
> already handles whatever C/C++ need from Unicode support POV and can handle
> it without any extra libraries.
> So, if we could avoid the extra dependency, it would be certainly better,
> unless you really need massive amounts of code from those libraries.
> libcpp already e.g. provides mapping of unicode character names to code
> points, determining which unicode characters can appear at the start or
> in the middle of identifiers, etc.

So that's exactly the answer that I supposed you or someone else would
give.  ;-)

That means, GCC/Rust has some investigation to do: whether what libcpp
contains is (a) sufficient for its needs, and (b) whether that code can
be reused/extracted/refactored in a sensible way, into GCC-level shared
source code file, to be used by several front ends (possibly via libcpp).
(I suppose GCC/Rust shouldn't link in libcpp directly.)


Thanks for the input, all!


Grüße
 Thomas
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