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SubjectRe: [PATCH v2 1/1] libbpf: replace typeof with __typeof__
On Wed, Jun 8, 2022 at 6:50 AM Daniel Borkmann <daniel@iogearbox.net> wrote:
>
> Hi James,
>
> On 6/8/22 8:40 AM, James Hilliard wrote:
> > It seems the gcc preprocessor breaks when typeof is used with
> > macros.
> >
> > Fixes errors like:
> > error: expected identifier or '(' before '#pragma'
> > 106 | SEC("cgroup/bind6")
> > | ^~~
> >
> > error: expected '=', ',', ';', 'asm' or '__attribute__' before '#pragma'
> > 114 | char _license[] SEC("license") = "GPL";
> > | ^~~
> >
> > Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
> > ---
> > Changes v1 -> v2:
> > - replace typeof with __typeof__ instead of changing pragma macros
> > ---
> > tools/lib/bpf/bpf_core_read.h | 16 ++++++++--------
> > tools/lib/bpf/bpf_helpers.h | 4 ++--
> > tools/lib/bpf/bpf_tracing.h | 24 ++++++++++++------------
> > tools/lib/bpf/btf.h | 4 ++--
> > tools/lib/bpf/libbpf_internal.h | 6 +++---
> > tools/lib/bpf/usdt.bpf.h | 6 +++---
> > tools/lib/bpf/xsk.h | 12 ++++++------
> > 7 files changed, 36 insertions(+), 36 deletions(-)
> >
> > diff --git a/tools/lib/bpf/bpf_core_read.h b/tools/lib/bpf/bpf_core_read.h
> > index fd48b1ff59ca..d3a88721c9e7 100644
> > --- a/tools/lib/bpf/bpf_core_read.h
> > +++ b/tools/lib/bpf/bpf_core_read.h
> > @@ -111,7 +111,7 @@ enum bpf_enum_value_kind {
> > })
> >
> > #define ___bpf_field_ref1(field) (field)
> > -#define ___bpf_field_ref2(type, field) (((typeof(type) *)0)->field)
> > +#define ___bpf_field_ref2(type, field) (((__typeof__(type) *)0)->field)
> > #define ___bpf_field_ref(args...) \
> > ___bpf_apply(___bpf_field_ref, ___bpf_narg(args))(args)
> >
>
> Can't we just add the below?
>
> #ifndef typeof
> # define typeof __typeof__
> #endif

From what I can tell it's not actually missing, but rather is
preprocessed differently
as the errors seem to be macro related.

I did also find this change which seems related:
https://github.com/torvalds/linux/commit/8faf7fc597d59b142af41ddd4a2d59485f75f88a

>
> Thanks,
> Daniel

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