GCC/Rust libgrust-v2/to-submit branch (was: [PATCH 2/3] build: Add libgrust as compilation modules)

[Thomas Schwinge <thomas@codesourcery.com>]

Hi!

Arthur and Pierre-Emmanuel have prepared a GCC/Rust libgrust-v2/to-submit
branch: <https://github.com/Rust-GCC/gccrs/tree/libgrust-v2/to-submit>.
In that one, most of the issues raised have been addressed, and which
I've now successfully "tested" in my different GCC configurations,
requiring just one additional change (see end of this email).  I'm using
"tested" in quotes here, as libgrust currently is still missing its
eventual content, and still is without actual users, so we may still be
up for surprises later on.  ;-)

On 2023-10-27T22:41:52+0200, I wrote:
> On 2023-09-27T00:25:16+0200, I wrote:
>> don't we also directly need to
>> incorporate here a few GCC/Rust master branch follow-on commits, like:
>>
>>   - commit 171ea4e2b3e202067c50f9c206974fbe1da691c0 "fixup: Fix bootstrap build"
>>   - commit 61cbe201029658c32e5c360823b9a1a17d21b03c "fixup: Fix missing build dependency"
>
> I've not yet run into the need for these two.  Let's please leave these
> out of the upstream submission for now, until we understand what exactly
> these are necessary for.

(Still the same.)

> However:
>
>>   - commit 6a8b207b9ef7f9038e0cae7766117428783825d8 "libgrust: Add dependency to libstdc++"
>
> ... this one definitely is necessary right now; see discussion in
> <https://inbox.sourceware.org/8734xv24dd.fsf@euler.schwinge.homeip.net>
> "Disable target libgrust if we're not building target libstdc++".

This one still isn't in the GCC/Rust libgrust-v2/to-submit branch -- but
having now tested that branch, I'm now no longer seeing the respective
build failure.  Isn't that change "libgrust: Add dependency to libstdc++"
still necessary, conceptually?  (Maybe we're just lucky, currently?)
I'll be sure to re-test in my different GCC configurations once libgrust
gains actual content and use.  (..., which might then re-expose the
original problem?)

> And:
>
>> (Not sure if all of these are necessary and/or if that's the complete
>> list; haven't looked up the corresponding GCC/Rust GitHub PRs.)
>>
>>> --- a/gcc/rust/config-lang.in
>>> +++ b/gcc/rust/config-lang.in
>>
>>> +target_libs="target-libffi target-libbacktrace target-libgrust"
>>
>> Please don't add back 'target-libffi' and 'target-libbacktrace' here;
>> just 'target-libgrust'.  (As is present in GCC/Rust master branch, and
>> per commit 7411eca498beb13729cc2acec77e68250940aa81
>> "Rust: Don't depend on unused 'target-libffi', 'target-libbacktrace'".)
>
> ... that change is necessary, too.

That's still unchanged in the GCC/Rust libgrust-v2/to-submit branch;
please apply to 'gcc/rust/config-lang.in':

    -target_libs="target-libffi target-libbacktrace target-libgrust"
    +target_libs=target-libgrust

Then, still should re-order the commits so that (re)generation of
auto-generated files comes before use of libgrust (so that later
bisection doesn't break), and move the 'contrib/gcc_update' update into
the commit that adds the auto-generated files.


Grüße
 Thomas
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