On Thu, 2024-09-12 at 09:05 +0800, Hou Tao wrote:
[...]
> > progs/cpumask_failure.c:19:33: error: use of undeclared identifier 'BTF_FIELDS_MAX'; did you mean 'BTF_KIND_MAX'?
> > 19 | struct kptr_nested_array_2 d_2[BTF_FIELDS_MAX + 1];
> > | ^~~~~~~~~~~~~~
> > | BTF_KIND_MAX
> >
> > [...]
>
> BTF_FIELDS_MAX should be defined in vmlinux.h. Could you please check
> whether or not it is present ? It seems that BPF CI reports the same
> problem for build-x86_64-llvm-17/build-x86_64-llvm-18 [1], but others
(did you mean to specify a ling for [1] ?)
> build are OK. Do you know is there anything special about
> build-x86_64-llvm-17/18 ?
>
Hm, this is interesting. I use LLVM 20.0.0git.
For BTF_FIELDS_MAX to be present in vmlinux.h it first has to be
present in vmlinux DWARF. However, the following output is empty:
$ llvm-dwarfdump vmlinux | grep BTF_FIELDS_MAX
While picking some other enum literal:
$ llvm-dwarfdump vmlinux | grep BTF_KIND_INT
DW_AT_name ("BTF_KIND_INT")
DW_AT_name ("BTF_KIND_INT")
...
Produce output.
Looks like LLVM20 drops info about BTF_FIELDS_MAX for some reason.
I will take a look at compiler internals, but you would need some
workaround for the test, unfortunately.
