bug#63267: gcc-toolchain is missing libstdc++.so

[John Kehayias via Bug reports for GNU Guix <bug-guix@gnu.org>]

Hi Christopher,

On Thu, May 04, 2023 at 11:05 AM, Christopher Rodriguez wrote:
>
> Sorry for the spam; Resending this without the bugs address, but with
> the issue's address.
>
> Christopher Rodriguez <yewscion@gmail.com> writes:
>
>>
>> Hello All,
>>
>> I noticed today that libstdc++.so.1 (and some others), which used to be
>> part of gcc:lib, are not included in any of the outputs of the
>> superceding `gcc-toolchain` package.
>>
>> Is there another method for getting these needed shared libraries in a
>> guix system at this point? It's entirely possible I'm missing something.
>>
>> I am CCing guix-devel@gnu.org per podiki[m]'s request.
>>
>> Thanks!

Thanks for opening this and cc'ing; this has come up with some
frequency on IRC, especially recently. In discussing there today, the
current reasoning is that usually one will just call g++ which knows
how to find libstdc++. So, gcc-toolchain does not include gcc:lib as
part of what it makes available.

I think what we (and when this comes up, others) are getting at are
some edge cases or different use cases where one wants to directly get
at libstdc++. Previously it was more direct to use gcc:lib; of course
one still can in code and/or cli with the proper call. For example,
guix build -e "(@@ (gnu packages gcc) gcc)" will download/build/show
the lib output of the (hidden) gcc package. Though I'm not sure how to
select just the lib output here.

My use case currently is in the FHS container where a binary wants to
find some libraries directly. Previously one would include the gcc:lib
package output in the guix shell call. Now some of those libraries can
be found elsewhere, like libgccjit, but libstdc++ seems to be the
trickier one. Open to other suggestions/workarounds, or thoughts on if
it is worthwhile to include gcc:lib in the gcc-toolchain package (or
make a gcc-toolchain:lib output?).

Thanks all!
John