RE: [PATCH 2/4] bpftool: Complete libbfd feature detection

[Roberto Sassu <roberto.sassu@huawei.com>]

> From: Quentin Monnet [mailto:quentin@isovalent.com]
> Sent: Wednesday, July 20, 2022 10:08 PM
> On Tue, 19 Jul 2022 at 18:06, Roberto Sassu <roberto.sassu@huawei.com>
> wrote:
> >
> > Commit 6e8ccb4f624a7 ("tools/bpf: properly account for libbfd variations")
> > sets the linking flags depending on which flavor of the libbfd feature was
> > detected.
> >
> > However, the flavors except libbfd cannot be detected, as they are not in
> > the feature list.
> >
> > Complete the list of features to detect by adding libbfd-liberty and
> > libbfd-liberty-z.
> >
> > Fixes: 6e8ccb4f624a7 ("tools/bpf: properly account for libbfd variations")
> > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> > ---
> >  tools/bpf/bpftool/Makefile | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
> > index 6b5b3a99f79d..4b09a5c3b9f1 100644
> > --- a/tools/bpf/bpftool/Makefile
> > +++ b/tools/bpf/bpftool/Makefile
> > @@ -93,8 +93,10 @@ INSTALL ?= install
> >  RM ?= rm -f
> >
> >  FEATURE_USER = .bpftool
> > -FEATURE_TESTS = libbfd disassembler-four-args libcap clang-bpf-co-re
> > -FEATURE_DISPLAY = libbfd disassembler-four-args libcap clang-bpf-co-re
> > +FEATURE_TESTS = libbfd libbfd-liberty libbfd-liberty-z \
> > +               disassembler-four-args libcap clang-bpf-co-re
> > +FEATURE_DISPLAY = libbfd libbfd-liberty libbfd-liberty-z \
> > +                 disassembler-four-args libcap clang-bpf-co-re
> 
> Do you know if there is a way to fold the different feature-libbfd-*
> features into a single one for FEATURE_DISPLAY? Or should the various
> features be all moved under feature-libbfd with multiple attempts,
> like you did for disassembler-four-args in patch 1? My concern is that
> users may think some features could be missing when they compile and
> see that detection fails for some items.

I thought about retrying. Hovewer, bpftool Makefile uses the
different flavors to determine exactly which linking flags to use.
Transparent retrying means that this information is lost.

Also very interesting, Ubuntu uses feature-libbfd for the shared
library, feature-libbfd-liberty-z for the static one. 

Roberto