On Thu, Sep 19, 2019 at 7:18 AM Ivan Khoronzhuk <ivan.khoronzhuk@xxxxxxxxxx> wrote: > > On Wed, Sep 18, 2019 at 02:29:53PM -0700, Andrii Nakryiko wrote: > >On Wed, Sep 18, 2019 at 3:35 AM Ivan Khoronzhuk > ><ivan.khoronzhuk@xxxxxxxxxx> wrote: > >> > >> On Tue, Sep 17, 2019 at 04:42:07PM -0700, Andrii Nakryiko wrote: > >> >On Mon, Sep 16, 2019 at 3:59 AM Ivan Khoronzhuk > >> ><ivan.khoronzhuk@xxxxxxxxxx> wrote: > >> >> > >> >> While compile natively, the hosts cflags and ldflags are equal to ones > >> >> used from HOSTCFLAGS and HOSTLDFLAGS. When cross compiling it should > >> >> have own, used for target arch. While verification, for arm, arm64 and > >> >> x86_64 the following flags were used alsways: > >> >> > >> >> -Wall > >> >> -O2 > >> >> -fomit-frame-pointer > >> >> -Wmissing-prototypes > >> >> -Wstrict-prototypes > >> >> > >> >> So, add them as they were verified and used before adding > >> >> Makefile.target, but anyway limit it only for cross compile options as > >> >> for host can be some configurations when another options can be used, > >> >> So, for host arch samples left all as is, it allows to avoid potential > >> >> option mistmatches for existent environments. > >> >> > >> >> Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@xxxxxxxxxx> > >> >> --- > >> >> samples/bpf/Makefile | 9 +++++++++ > >> >> 1 file changed, 9 insertions(+) > >> >> > >> >> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile > >> >> index 1579cc16a1c2..b5c87a8b8b51 100644 > >> >> --- a/samples/bpf/Makefile > >> >> +++ b/samples/bpf/Makefile > >> >> @@ -178,8 +178,17 @@ CLANG_EXTRA_CFLAGS := $(ARM_ARCH_SELECTOR) > >> >> TPROGS_CFLAGS += $(ARM_ARCH_SELECTOR) > >> >> endif > >> >> > >> >> +ifdef CROSS_COMPILE > >> >> +TPROGS_CFLAGS += -Wall > >> >> +TPROGS_CFLAGS += -O2 > >> > > >> >Specifying one arg per line seems like overkill, put them in one line? > >> Will combine. > >> > >> > > >> >> +TPROGS_CFLAGS += -fomit-frame-pointer > >> > > >> >Why this one? > >> I've explained in commit msg. The logic is to have as much as close options > >> to have smiliar binaries. As those options are used before for hosts and kinda > >> cross builds - better follow same way. > > > >I'm just asking why omit frame pointers and make it harder to do stuff > >like profiling? What performance benefits are we seeking for in BPF > >samples? > > > >> > >> > > >> >> +TPROGS_CFLAGS += -Wmissing-prototypes > >> >> +TPROGS_CFLAGS += -Wstrict-prototypes > >> > > >> >Are these in some way special that we want them in cross-compile mode only? > >> > > >> >All of those flags seem useful regardless of cross-compilation or not, > >> >shouldn't they be common? I'm a bit lost about the intent here... > >> They are common but split is needed to expose it at least. Also host for > >> different arches can have some own opts already used that shouldn't be present > >> for cross, better not mix it for safety. > > > >We want -Wmissing-prototypes and -Wstrict-prototypes for cross-compile > >and non-cross-compile cases, right? So let's specify them as common > >set of options, instead of relying on KBUILD_HOSTCFLAGS or > >HOST_EXTRACFLAGS to have them. Otherwise we'll be getting extra > >warnings for just cross-compile case, which is not good. If you are > >worrying about having duplicate -W flags, seems like it's handled by > >GCC already, so shouldn't be a problem. > > Ok, lets drop omit-frame-pointer. > > But then, lets do more radical step and drop > KBUILD_HOSTCFLAGS & HOST_EXTRACFLAG in this patch: Yeah, let's do this, if you confirmed that everything still works (and I don't see a reason why it shouldn't). Thanks. > > -ifdef CROSS_COMPILE > +TPROGS_CFLAGS += -Wall -O2 > +TPROGS_CFLAGS += -Wmissing-prototypes > +TPROGS_CFLAGS += -Wstrict-prototypes > -else > -TPROGS_LDLIBS := $(KBUILD_HOSTLDLIBS) > -TPROGS_CFLAGS += $(KBUILD_HOSTCFLAGS) $(HOST_EXTRACFLAGS) > -endif > > At least it allows to use same options always for both, native and cross. > > I verified on native x86_64, arm64 and arm and cross for arm and arm64, > but should work for others, at least it can be tuned explicitly and > no need to depend on KBUILD and use "cross" fork here. Yep, I like it. > > -- > Regards, > Ivan Khoronzhuk
