GMP GCC C++ Hurd cross-build failure on core-updates

[zamfofex]

Hello, Guix! I have been trying to update the Hurd packages to their latest 
commits in the hopes that I can eventually get networking with netdde 
functioning.

In <https://issues.guix.gnu.org/51770>, I got something that seemed to be 
working at first (at least it progressed farther than the status quo at the 
time), but eventually I got an error that seemed related to Mig, which I had 
not updated in that patch set.

Updating Mig required a more recent glibc than what was available in Guix at 
the time, so I worked on <https://issues.guix.gnu.org/54832> to update glibc.

Now that the recent glibc is on core-updates, I picked up my work once again. I 
updated the packages to the latest commits, and updated Mig! However, I ran 
into an issue while trying to build a system image. The issue is that GMP fails 
to cross‐compile during the ‘configure’ phase becase the cross‐compiling ‘g++’ 
is not functional.

When checking whether ‘g++’ can compile executables during ‘configure’, ‘g++’ 
is unable to link the executables because some ‘pthread_*’ symbols required by 
libstdc++ are missing from libc. And when checking using ‘readelf’, they are 
indeed missing from the cross‐built libc, which instead contains similar 
‘__pthread_*’ symbols.

I don’t know for sure what the issue is, but I highly suspect libstdc++ is 
being compiled against the native glibc headers, rather than the cross‐built 
glibc headers like it should.

Note: Currently, trying to cross‐build packages from core‐updates for the Hurd 
will fail while compiling glibc, since the Hurd package is too outdated for 
that version of glibc.

I’ll attach a diff (for core-updates) with the updated Hurd packages to this 
email. To verify the behavior I’m describing, try running:

- - - - -
./pre-inst-env guix build --target=i586-pc-gnu gmp
- - - - -

Any kind of assistance would be appreciated! Thanks in advance.

hurd.diff
Description: Binary data