Re: [PATCH bpf] libbpf: fix version identification on busybox

[Ivan Khoronzhuk]

On Thu, Sep 19, 2019 at 01:02:40PM -0700, Andrii Nakryiko wrote:
> On Thu, Sep 19, 2019 at 11:22 AM Ivan Khoronzhuk
> <ivan.khoronzhuk@xxxxxxxxxx> wrote:
> > It's very often for embedded to have stripped version of sort in
> > busybox, when no -V option present. It breaks build natively on target
> > board causing recursive loop.
> >
> > BusyBox v1.24.1 (2019-04-06 04:09:16 UTC) multi-call binary. \
> > Usage: sort [-nrugMcszbdfimSTokt] [-o FILE] [-k \
> > start[.offset][opts][,end[.offset][opts]] [-t CHAR] [FILE]...
> >
> > Lets modify command a little to avoid -V option.
> >
> > Fixes: dadb81d0afe732 ("libbpf: make libbpf.map source of truth for libbpf version")
> >
> > Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@xxxxxxxxxx>
> > ---
> >
> > Based on bpf/master
> >
> >  tools/lib/bpf/Makefile | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
> > index c6f94cffe06e..a12490ad6215 100644
> > --- a/tools/lib/bpf/Makefile
> > +++ b/tools/lib/bpf/Makefile
> > @@ -3,7 +3,7 @@
> >
> >  LIBBPF_VERSION := $(shell \
> >         grep -oE '^LIBBPF_([0-9.]+)' libbpf.map | \
> > -       sort -rV | head -n1 | cut -d'_' -f2)
> > +       cut -d'_' -f2 | sort -r | head -n1)
>
> You can't just sort alphabetically, because:
>
> 1.2
> 1.11
>
> should be in that order. See discussion on mailing thread for original commit.

if X1.X2.X3, where X = {0,1,....99999}
Then it can be:

-LIBBPF_VERSION := $(shell \
-       grep -oE '^LIBBPF_([0-9.]+)' libbpf.map | \
-       sort -rV | head -n1 | cut -d'_' -f2)
+_LBPFLIST := $(patsubst %;,%,$(patsubst LIBBPF_%,%,$(filter LIBBPF_%, \
+           $(shell cat libbpf.map))))
+_LBPFLIST2 := $(foreach v,$(_LBPFLIST), \
+               $(subst $() $(),,$(foreach n,$(subst .,$() $(),$(v)), \
+                       $(shell printf "%05d" $(n)))))
+_LBPF_VER := $(word $(words $(sort $(_LBPFLIST2))), $(sort $(_LBPFLIST2)))
+LIBBPF_VERSION := $(patsubst %_$(_LBPF_VER),%,$(filter %_$(_LBPF_VER), \
+        $(join $(addsuffix _, $(_LBPFLIST)),$(_LBPFLIST2))))

It's bigger but avoids invocations of grep/sort/cut/head, only cat/printf
, thus -V option also.

> >  LIBBPF_MAJOR_VERSION := $(firstword $(subst ., ,$(LIBBPF_VERSION)))
> >
> >  MAKEFLAGS += --no-print-directory
> > --
> > 2.17.1

--
Regards,
Ivan Khoronzhuk