Re: [Xen-devel] [RFC 2/7] WIP: Compilation with ARM DS-6 compiler

[Julien Grall <julien.grall.oss@xxxxxxxxx>]

On Thu, 14 Nov 2019, 02:15 Artem Mygaiev, <Artem_Mygaiev@xxxxxxxx> wrote:

Hi Jan,

Sorry for delayed reply

On Thu, 2019-11-07 at 08:31 +0100, Jan Beulich wrote:
> On 06.11.2019 23:08, Artem Mygaiev wrote:
> > On Wed, Nov 6, 2019 at 4:28 PM Jan Beulich <
> > jbeulich@xxxxxxxx
> > > wrote:
> > > On 06.11.2019 10:19, Andrii Anisov wrote:
> > > > --- a/Config.mk
> > > > +++ b/Config.mk
> > > > @@ -221,7 +221,9 @@ CFLAGS += -Wall -Wstrict-prototypes
> > > >
> > > >  $(call cc-option-add,HOSTCFLAGS,HOSTCC,-Wdeclaration-after-
> > > > statement)
> > > >  $(call cc-option-add,CFLAGS,CC,-Wdeclaration-after-statement)
> > > > +ifneq ($(armds),y)
> > > >  $(call cc-option-add,CFLAGS,CC,-Wno-unused-but-set-variable)
> > > > +endif
> > > >  $(call cc-option-add,CFLAGS,CC,-Wno-unused-local-typedefs)
> > > >
> > > >  LDFLAGS += $(foreach i, $(EXTRA_LIB), -L$(i))
> > >
> > > ... this would be necessary.
> >
> > I am very sorry, this patch does not have a proper description
> > indeed.
> >
> > For this particular change - arm clang does not undestand
> > -Wno-unused-but-set-variable
> > option at all, that is why it is under !$(armds)
>
> But avoiding to add options which the compiler doesn't understand
> is the purpose of using cc-option-add, rather than blindly
> adding
> them to CFLAGS. What am I missing here?

You are right, the script shall check the compiler option and avoid
including it to CFLAGS. But armclang require '--target=...' to be
specified in order to operate properly, and the proper fix shall be
something like this (instead of 'ifneq' hack above):

diff --git a/Config.mk b/Config.mk
index 01487a7..abe8e44 100644
--- a/Config.mk
+++ b/Config.mk
@@ -107,7 +107,7 @@ cc-option = $(shell if test -z "`echo 'void*p=1;' | \
 # Usage: $(call cc-option-add CFLAGS,CC,-march=winchip-c6)
 cc-option-add = $(eval $(call cc-option-add-closure,$(1),$(2),$(3)))
 define cc-option-add-closure
-    ifneq ($$(call cc-option,$$($(2)),$(3),n),n)
+    ifneq ($$(call cc-option,$$($(2) $(1)),$(3),n),n)
         $(1) += $(3)
     endif
 endef

so that CFLAGS that are already defined and include '--target=...'
option from config/arm*.mk are passed to compiler to make it happy. I
am not sure if this breaks anything else so decided to go with ugly
'ifneq' hack and check how this can be solved later on.

Why not including --target in CC variable as this was suggested for clang?

Cheers,

-- 

Julien Grall

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