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>>>>       bpf_core_enum_value_exists(enum e, TWO); >>>> >>>> Compiling this with clang-12 >>>> (12.0.0-++20210225092616+e0e6b1e39e7e-1~exp1~20210225083321.50) gives >>>> me the following: >>>> >>>> internal/btf/testdata/relocs.c:66:2: error: >>>> __builtin_preserve_enum_value argument 1 invalid >>>>           enum_value_exists(enum e, TWO); >>>>           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >>>> internal/btf/testdata/relocs.c:53:8: note: expanded from macro >>>> 'enum_value_exists' >>>>                   if (!bpf_core_enum_value_exists(t, v)) { \ >>>>                        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >>>> internal/btf/testdata/bpf_core_read.h:168:32: note: expanded from >>>> macro 'bpf_core_enum_value_exists' >>>>           __builtin_preserve_enum_value(*(typeof(enum_type) >>>> *)enum_value, BPF_ENUMVAL_EXISTS) >>>> >>>> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >>> >>> Andrii can comment on MACRO failures. >> >> Yeah, I ran into this a long time ago as well... >> >> I don't actually know why this doesn't work for zeroes. I've tried to >> write that macro in a bit different way, but Clang rejects it: >> >> __builtin_preserve_enum_value(({typeof(enum_type) ___xxx = >> (enum_value); *(typeof(enum_type)*)&___xxx;}), BPF_ENUMVAL_EXISTS) >> >> And something as straightforward as >> >> __builtin_preserve_enum_value((typeof(enum_type))(enum_value), >> BPF_ENUMVAL_EXISTS) >> >> doesn't work as well. >> >> Yonghong, any idea how to write such a macro to work in all cases? Or >> why those alternatives don't work? I only get " error: >> __builtin_preserve_enum_value argument 1 invalid" with no more >> details, so hard to do anything about this. > > This is a clang BPF bug. In certain number classification system, > clang considers 0 as NULL and non-0 as INTEGER. I only checked > INTEGER and hence only non-0 works. All my tests has non-zero > enum values :-( > > Will fix the issue soon. Thanks for reporting! Just pushed the fix (https://reviews.llvm.org/D97659) to llvm trunk this morning. Also filed a request (https://bugs.llvm.org/show_bug.cgi?id=49391) to backport the fix to 12.0.1 release. it is too late to be included in 12.0.0 release. Thanks! > >> >> >>> >>>> >>>> Changing the definition of the enum to >>>> >>>>       enum e { TWO = 1 } >>>> >>>> compiles successfully. I get the same result for any enum value that >>>> is zero. Is this expected? >>> >>> IIRC, libbpf will try to do relocation against vmlinux BTF. >>> So here, "enum e" probably does not exist in vmlinux BTF, so >>> the builtin will return 0. You can try some enum type >>> existing in vmlinux BTF to see what happens. >>> >>>> >>>> Best >>>> Lorenz >>>>