Re: Kernel 5.5.4 build fail for BPF-selftests with latest LLVM

On Wed, Feb 19, 2020 at 4:30 AM Jesper Dangaard Brouer
[off-list ref] wrote:

I'm willing to help out, such that we can do either version or feature
detection, to either skip compiling specific test programs or at least
give users a proper warning of they are using a too "old" LLVM version.

...

progs/test_core_reloc_bitfields_probed.c:47:13: error: use of unknown builtin '__builtin_preserve_field_info' [-Wimplicit-function-declaration]
        out->ub1 = BPF_CORE_READ_BITFIELD_PROBED(in, ub1);

imo this is proper warning message already.