Undefined symbol __rbitll on Linux ARM with 3.2.0-rc1

[oscarbenjamin]

I was testing 3.2.0-rc1 and found that it failed to build on Linux ARM in CI:
flintlib/python-flint#264

The build fails with:

2025-03-03T12:41:33.7528498Z   CC  ulong_extras/primitive_root_prime.c
2025-03-03T12:41:33.7529610Z /project/.local/src/flint-3.2.0-rc1/src/ulong_extras/revbin.c: In function ‘n_revbin’:
2025-03-03T12:41:33.7538559Z /project/.local/src/flint-3.2.0-rc1/src/ulong_extras/revbin.c:22:9: error: implicit declaration of function ‘__rbitll’ [-Werror=implicit-function-declaration]
2025-03-03T12:41:33.7539839Z    22 |     n = __rbitll(n);
2025-03-03T12:41:33.7540559Z       |         ^~~~~~~~
2025-03-03T12:41:33.7618319Z /project/.local/src/flint-3.2.0-rc1/src/ulong_extras/revbin.c: At top level:
2025-03-03T12:41:33.7625654Z cc1: note: unrecognized command-line option ‘-Wno-stringop-overread’ may have been intended to silence earlier diagnostics
2025-03-03T12:41:33.7638086Z cc1: some warnings being treated as errors
2025-03-03T12:41:33.7729840Z make: *** [build/ulong_extras/revbin.lo] Error 1

FLINT's main branch builds fine though so I guess the problem is already fixed (although I'm not sure by what).

I just want to check that the fix will make it into 3.2.0 final...

Also GitHub Actions recently added Linux ARM runners which is what I am using to test this. Are those tested in FLINT's CI?

To use the ARM runners you can just set:

runs-on: ubuntu-24.04-arm

[albinahlback]

That's weird. It should be defined according to ARM C language extension. I'll look into it before we release 3.2.0.