| Message ID | 20200117105358.607910-11-anthony.perard@citrix.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | xen: Build system improvements | expand |
On 17.01.2020 11:53, Anthony PERARD wrote: > We would like to calculate CFLAGS once and before calling Rules.mk, > so the variable CFLAGS needs to have the same value across the whole > build. Thus we need a new variable where some flags can change > depending on the target name. > > Both the dependency and __OBJECT_FILE__ are such flags that change > depending on the target, so there are move out of $(CFLAGS). I'm afraid I don't understand: Being a delayed expansion (or "recursively expanded") variable, what problem is there when CFLAGS references $@? Is there a plan to change the variable's flavor? If so, I'd like to ask for this to be mentioned here. "Calculate once", at least to me, doesn't imply this. > @@ -141,9 +137,16 @@ endif > # Always build obj-bin files as binary even if they come from C source. > $(obj-bin-y): CFLAGS := $(filter-out -flto,$(CFLAGS)) > > +c_flags = -MMD -MF $(@D)/.$(@F).d \ > + $(CFLAGS) \ > + '-D__OBJECT_FILE__="$@"' > + > +a_flags = -MMD -MF $(@D)/.$(@F).d \ > + $(AFLAGS) Is there a reason both get extended over multiple lines? > --- a/xen/include/Makefile > +++ b/xen/include/Makefile > @@ -64,7 +64,7 @@ compat/%.h: compat/%.i Makefile $(BASEDIR)/tools/compat-build-header.py > mv -f $@.new $@ > > compat/%.i: compat/%.c Makefile > - $(CPP) $(filter-out -Wa$(comma)% -M% %.d -include %/include/xen/config.h,$(CFLAGS)) $(cppflags-y) -o $@ $< > + $(CPP) $(filter-out -Wa$(comma)% -M% %.d -include %/include/xen/config.h,$(c_flags)) $(cppflags-y) -o $@ $< I think this wants to continue to reference $(CFLAGS) and instead have the -M% and %.d patterns dropped. Similarly I guess as-insn in Config.mk could then have these two patterns dropped. Jan
On Thu, Jan 30, 2020 at 02:29:42PM +0100, Jan Beulich wrote: > On 17.01.2020 11:53, Anthony PERARD wrote: > > We would like to calculate CFLAGS once and before calling Rules.mk, > > so the variable CFLAGS needs to have the same value across the whole > > build. Thus we need a new variable where some flags can change > > depending on the target name. > > > > Both the dependency and __OBJECT_FILE__ are such flags that change > > depending on the target, so there are move out of $(CFLAGS). > > I'm afraid I don't understand: Being a delayed expansion (or > "recursively expanded") variable, what problem is there when CFLAGS > references $@? Is there a plan to change the variable's flavor? If > so, I'd like to ask for this to be mentioned here. "Calculate once", > at least to me, doesn't imply this. If I rewrite the first paragraph thus, would that be better? In a later patch, we want to calculate the CFLAGS in xen/Makefile, then export it. So have Rules.mk use a CFLAGS from the environment variables. This will mean that if Rules.mk or a Makefile modify CFLAGS for a target, the modification propagates to other targets. Thus we will need a different variable name than the one from the environment which can have a different value for each target. > > @@ -141,9 +137,16 @@ endif > > # Always build obj-bin files as binary even if they come from C source. > > $(obj-bin-y): CFLAGS := $(filter-out -flto,$(CFLAGS)) > > > > +c_flags = -MMD -MF $(@D)/.$(@F).d \ > > + $(CFLAGS) \ > > + '-D__OBJECT_FILE__="$@"' > > + > > +a_flags = -MMD -MF $(@D)/.$(@F).d \ > > + $(AFLAGS) > > Is there a reason both get extended over multiple lines? Beside that it looks cleaner to me, not really. > > --- a/xen/include/Makefile > > +++ b/xen/include/Makefile > > @@ -64,7 +64,7 @@ compat/%.h: compat/%.i Makefile $(BASEDIR)/tools/compat-build-header.py > > mv -f $@.new $@ > > > > compat/%.i: compat/%.c Makefile > > - $(CPP) $(filter-out -Wa$(comma)% -M% %.d -include %/include/xen/config.h,$(CFLAGS)) $(cppflags-y) -o $@ $< > > + $(CPP) $(filter-out -Wa$(comma)% -M% %.d -include %/include/xen/config.h,$(c_flags)) $(cppflags-y) -o $@ $< > > I think this wants to continue to reference $(CFLAGS) and instead have > the -M% and %.d patterns dropped. Similarly I guess as-insn in Config.mk > could then have these two patterns dropped. It's probably a good idea to keep using CFLAGS, I'll look into it. As to change as-insn, I can move it out of Config.mk and then change it. I'll look into that as well. Thanks,
On 03.02.2020 13:17, Anthony PERARD wrote: > On Thu, Jan 30, 2020 at 02:29:42PM +0100, Jan Beulich wrote: >> On 17.01.2020 11:53, Anthony PERARD wrote: >>> We would like to calculate CFLAGS once and before calling Rules.mk, >>> so the variable CFLAGS needs to have the same value across the whole >>> build. Thus we need a new variable where some flags can change >>> depending on the target name. >>> >>> Both the dependency and __OBJECT_FILE__ are such flags that change >>> depending on the target, so there are move out of $(CFLAGS). >> >> I'm afraid I don't understand: Being a delayed expansion (or >> "recursively expanded") variable, what problem is there when CFLAGS >> references $@? Is there a plan to change the variable's flavor? If >> so, I'd like to ask for this to be mentioned here. "Calculate once", >> at least to me, doesn't imply this. > > If I rewrite the first paragraph thus, would that be better? > > In a later patch, we want to calculate the CFLAGS in xen/Makefile, > then export it. So have Rules.mk use a CFLAGS from the environment > variables. This will mean that if Rules.mk or a Makefile modify > CFLAGS for a target, the modification propagates to other targets. > Thus we will need a different variable name than the one from the > environment which can have a different value for each target. I think this is better, yes, albeit I'm still a little unhappy about the uses of "target" here: It makes it look to me as if this was primarily about things like abc.o: CFLAGS += ... where, unless its rule invokes make, I don't think the adjustment would propagate anywhere. Instead aiui what you refer to is solely an effect from the subdir traversal the build system does? >>> @@ -141,9 +137,16 @@ endif >>> # Always build obj-bin files as binary even if they come from C source. >>> $(obj-bin-y): CFLAGS := $(filter-out -flto,$(CFLAGS)) >>> >>> +c_flags = -MMD -MF $(@D)/.$(@F).d \ >>> + $(CFLAGS) \ >>> + '-D__OBJECT_FILE__="$@"' >>> + >>> +a_flags = -MMD -MF $(@D)/.$(@F).d \ >>> + $(AFLAGS) >> >> Is there a reason both get extended over multiple lines? > > Beside that it looks cleaner to me, not really. Apparently a matter of taste then. I generally consider trailing backslashes a little "unclean", and hence would prefer to avoid them if I can. >>> --- a/xen/include/Makefile >>> +++ b/xen/include/Makefile >>> @@ -64,7 +64,7 @@ compat/%.h: compat/%.i Makefile $(BASEDIR)/tools/compat-build-header.py >>> mv -f $@.new $@ >>> >>> compat/%.i: compat/%.c Makefile >>> - $(CPP) $(filter-out -Wa$(comma)% -M% %.d -include %/include/xen/config.h,$(CFLAGS)) $(cppflags-y) -o $@ $< >>> + $(CPP) $(filter-out -Wa$(comma)% -M% %.d -include %/include/xen/config.h,$(c_flags)) $(cppflags-y) -o $@ $< >> >> I think this wants to continue to reference $(CFLAGS) and instead have >> the -M% and %.d patterns dropped. Similarly I guess as-insn in Config.mk >> could then have these two patterns dropped. > > It's probably a good idea to keep using CFLAGS, I'll look into it. > As to change as-insn, I can move it out of Config.mk and then change it. > I'll look into that as well. Thank you. Jan
diff --git a/xen/Rules.mk b/xen/Rules.mk index d20521cc9ec1..c98d5372f3db 100644 --- a/xen/Rules.mk +++ b/xen/Rules.mk @@ -57,7 +57,6 @@ CFLAGS += -Werror -Wredundant-decls -Wno-pointer-arith $(call cc-option-add,CFLAGS,CC,-Wvla) CFLAGS += -pipe -D__XEN__ -include $(BASEDIR)/include/xen/config.h CFLAGS-$(CONFIG_DEBUG_INFO) += -g -CFLAGS += '-D__OBJECT_FILE__="$@"' ifneq ($(CONFIG_CC_IS_CLANG),y) # Clang doesn't understand this command line argument, and doesn't appear to @@ -70,9 +69,6 @@ AFLAGS-y += -D__ASSEMBLY__ ALL_OBJS := $(ALL_OBJS-y) -# Get gcc to generate the dependencies for us. -CFLAGS-y += -MMD -MF $(@D)/.$(@F).d - CFLAGS += $(CFLAGS-y) # allow extra CFLAGS externally via EXTRA_CFLAGS_XEN_CORE CFLAGS += $(EXTRA_CFLAGS_XEN_CORE) @@ -141,9 +137,16 @@ endif # Always build obj-bin files as binary even if they come from C source. $(obj-bin-y): CFLAGS := $(filter-out -flto,$(CFLAGS)) +c_flags = -MMD -MF $(@D)/.$(@F).d \ + $(CFLAGS) \ + '-D__OBJECT_FILE__="$@"' + +a_flags = -MMD -MF $(@D)/.$(@F).d \ + $(AFLAGS) + built_in.o: $(obj-y) $(extra-y) ifeq ($(obj-y),) - $(CC) $(CFLAGS) -c -x c /dev/null -o $@ + $(CC) $(c_flags) -c -x c /dev/null -o $@ else ifeq ($(CONFIG_LTO),y) $(LD_LTO) -r -o $@ $(filter-out $(extra-y),$^) @@ -154,7 +157,7 @@ endif built_in_bin.o: $(obj-bin-y) $(extra-y) ifeq ($(obj-bin-y),) - $(CC) $(AFLAGS) -c -x assembler /dev/null -o $@ + $(CC) $(a_flags) -c -x assembler /dev/null -o $@ else $(LD) $(LDFLAGS) -r -o $@ $(filter-out $(extra-y),$^) endif @@ -173,7 +176,7 @@ SRCPATH := $(patsubst $(BASEDIR)/%,%,$(CURDIR)) %.o: %.c Makefile ifeq ($(CONFIG_ENFORCE_UNIQUE_SYMBOLS),y) - $(CC) $(CFLAGS) -c $< -o $(@D)/.$(@F).tmp + $(CC) $(c_flags) -c $< -o $(@D)/.$(@F).tmp ifeq ($(CONFIG_CC_IS_CLANG),y) $(OBJCOPY) --redefine-sym $<=$(SRCPATH)/$< $(@D)/.$(@F).tmp $@ else @@ -181,11 +184,11 @@ else endif rm -f $(@D)/.$(@F).tmp else - $(CC) $(CFLAGS) -c $< -o $@ + $(CC) $(c_flags) -c $< -o $@ endif %.o: %.S Makefile - $(CC) $(AFLAGS) -c $< -o $@ + $(CC) $(a_flags) -c $< -o $@ SPECIAL_DATA_SECTIONS := rodata $(foreach a,1 2 4 8 16, \ $(foreach w,1 2 4, \ @@ -206,13 +209,13 @@ $(filter %.init.o,$(obj-y) $(obj-bin-y) $(extra-y)): %.init.o: %.o Makefile $(OBJCOPY) $(foreach s,$(SPECIAL_DATA_SECTIONS),--rename-section .$(s)=.init.$(s)) $< $@ %.i: %.c Makefile - $(CPP) $(filter-out -Wa$(comma)%,$(CFLAGS)) $< -o $@ + $(CPP) $(filter-out -Wa$(comma)%,$(c_flags)) $< -o $@ %.s: %.c Makefile - $(CC) $(filter-out -Wa$(comma)%,$(CFLAGS)) -S $< -o $@ + $(CC) $(filter-out -Wa$(comma)%,$(c_flags)) -S $< -o $@ # -std=gnu{89,99} gets confused by # as an end-of-line comment marker %.s: %.S Makefile - $(CPP) $(filter-out -Wa$(comma)%,$(AFLAGS)) $< -o $@ + $(CPP) $(filter-out -Wa$(comma)%,$(a_flags)) $< -o $@ -include $(DEPS_INCLUDE) diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile index 1044c2298a05..7f1427630b96 100644 --- a/xen/arch/arm/Makefile +++ b/xen/arch/arm/Makefile @@ -121,10 +121,10 @@ $(TARGET)-syms: prelink.o xen.lds rm -f $(@D)/.$(@F).[0-9]* asm-offsets.s: $(TARGET_SUBARCH)/asm-offsets.c - $(CC) $(filter-out -flto,$(CFLAGS)) -S -o $@ $< + $(CC) $(filter-out -flto,$(c_flags)) -S -o $@ $< xen.lds: xen.lds.S - $(CC) -P -E -Ui386 $(AFLAGS) -o $@ $< + $(CC) -P -E -Ui386 $(a_flags) -o $@ $< sed -e 's/xen\.lds\.o:/xen\.lds:/g' <.xen.lds.d >.xen.lds.d.new mv -f .xen.lds.d.new .xen.lds.d diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile index 461d1f3dc2a6..472e3fadb719 100644 --- a/xen/arch/x86/Makefile +++ b/xen/arch/x86/Makefile @@ -225,7 +225,7 @@ efi/boot.init.o efi/runtime.o efi/compat.o efi/buildid.o efi/relocs-dummy.o: $(B efi/boot.init.o efi/runtime.o efi/compat.o efi/buildid.o efi/relocs-dummy.o: ; asm-offsets.s: $(TARGET_SUBARCH)/asm-offsets.c $(BASEDIR)/include/asm-x86/asm-macros.h - $(CC) $(filter-out -Wa$(comma)% -flto,$(CFLAGS)) -S -o $@ $< + $(CC) $(filter-out -Wa$(comma)% -flto,$(c_flags)) -S -o $@ $< asm-macros.i: CFLAGS += -D__ASSEMBLY__ -P @@ -241,12 +241,12 @@ $(BASEDIR)/include/asm-x86/asm-macros.h: asm-macros.i Makefile $(call move-if-changed,$@.new,$@) xen.lds: xen.lds.S - $(CC) -P -E -Ui386 $(filter-out -Wa$(comma)%,$(AFLAGS)) -o $@ $< + $(CC) -P -E -Ui386 $(filter-out -Wa$(comma)%,$(a_flags)) -o $@ $< sed -e 's/.*\.lds\.o:/$(@F):/g' <.$(@F).d >.$(@F).d.new mv -f .$(@F).d.new .$(@F).d efi.lds: xen.lds.S - $(CC) -P -E -Ui386 -DEFI $(filter-out -Wa$(comma)%,$(AFLAGS)) -o $@ $< + $(CC) -P -E -Ui386 -DEFI $(filter-out -Wa$(comma)%,$(a_flags)) -o $@ $< sed -e 's/.*\.lds\.o:/$(@F):/g' <.$(@F).d >.$(@F).d.new mv -f .$(@F).d.new .$(@F).d diff --git a/xen/arch/x86/mm/Makefile b/xen/arch/x86/mm/Makefile index d87dc0aa6eeb..a2431fde6bb4 100644 --- a/xen/arch/x86/mm/Makefile +++ b/xen/arch/x86/mm/Makefile @@ -12,10 +12,10 @@ obj-$(CONFIG_HVM) += p2m-ept.o p2m-pod.o obj-y += paging.o guest_walk_%.o: guest_walk.c Makefile - $(CC) $(CFLAGS) -DGUEST_PAGING_LEVELS=$* -c $< -o $@ + $(CC) $(c_flags) -DGUEST_PAGING_LEVELS=$* -c $< -o $@ guest_walk_%.i: guest_walk.c Makefile - $(CPP) $(filter-out -Wa$(comma)%,$(CFLAGS)) -DGUEST_PAGING_LEVELS=$* -c $< -o $@ + $(CPP) $(filter-out -Wa$(comma)%,$(c_flags)) -DGUEST_PAGING_LEVELS=$* -c $< -o $@ guest_walk_%.s: guest_walk.c Makefile - $(CC) $(filter-out -Wa$(comma)%,$(CFLAGS)) -DGUEST_PAGING_LEVELS=$* -S $< -o $@ + $(CC) $(filter-out -Wa$(comma)%,$(c_flags)) -DGUEST_PAGING_LEVELS=$* -S $< -o $@ diff --git a/xen/arch/x86/mm/hap/Makefile b/xen/arch/x86/mm/hap/Makefile index b14a9aff93d2..22e7ad54bd33 100644 --- a/xen/arch/x86/mm/hap/Makefile +++ b/xen/arch/x86/mm/hap/Makefile @@ -6,10 +6,10 @@ obj-y += nested_hap.o obj-y += nested_ept.o guest_walk_%level.o: guest_walk.c Makefile - $(CC) $(CFLAGS) -DGUEST_PAGING_LEVELS=$* -c $< -o $@ + $(CC) $(c_flags) -DGUEST_PAGING_LEVELS=$* -c $< -o $@ guest_walk_%level.i: guest_walk.c Makefile - $(CPP) $(filter-out -Wa$(comma)%,$(CFLAGS)) -DGUEST_PAGING_LEVELS=$* -c $< -o $@ + $(CPP) $(filter-out -Wa$(comma)%,$(c_flags)) -DGUEST_PAGING_LEVELS=$* -c $< -o $@ guest_walk_%level.s: guest_walk.c Makefile - $(CC) $(filter-out -Wa$(comma)%,$(CFLAGS)) -DGUEST_PAGING_LEVELS=$* -S $< -o $@ + $(CC) $(filter-out -Wa$(comma)%,$(c_flags)) -DGUEST_PAGING_LEVELS=$* -S $< -o $@ diff --git a/xen/arch/x86/mm/shadow/Makefile b/xen/arch/x86/mm/shadow/Makefile index ff03a9937f9b..23d3ff10802c 100644 --- a/xen/arch/x86/mm/shadow/Makefile +++ b/xen/arch/x86/mm/shadow/Makefile @@ -7,10 +7,10 @@ obj-y += none.o endif guest_%.o: multi.c Makefile - $(CC) $(CFLAGS) -DGUEST_PAGING_LEVELS=$* -c $< -o $@ + $(CC) $(c_flags) -DGUEST_PAGING_LEVELS=$* -c $< -o $@ guest_%.i: multi.c Makefile - $(CPP) $(filter-out -Wa$(comma)%,$(CFLAGS)) -DGUEST_PAGING_LEVELS=$* -c $< -o $@ + $(CPP) $(filter-out -Wa$(comma)%,$(c_flags)) -DGUEST_PAGING_LEVELS=$* -c $< -o $@ guest_%.s: multi.c Makefile - $(CC) $(filter-out -Wa$(comma)%,$(CFLAGS)) -DGUEST_PAGING_LEVELS=$* -S $< -o $@ + $(CC) $(filter-out -Wa$(comma)%,$(c_flags)) -DGUEST_PAGING_LEVELS=$* -S $< -o $@ diff --git a/xen/include/Makefile b/xen/include/Makefile index 433bad9055b2..83131c2472f5 100644 --- a/xen/include/Makefile +++ b/xen/include/Makefile @@ -64,7 +64,7 @@ compat/%.h: compat/%.i Makefile $(BASEDIR)/tools/compat-build-header.py mv -f $@.new $@ compat/%.i: compat/%.c Makefile - $(CPP) $(filter-out -Wa$(comma)% -M% %.d -include %/include/xen/config.h,$(CFLAGS)) $(cppflags-y) -o $@ $< + $(CPP) $(filter-out -Wa$(comma)% -M% %.d -include %/include/xen/config.h,$(c_flags)) $(cppflags-y) -o $@ $< compat/%.c: public/%.h xlat.lst Makefile $(BASEDIR)/tools/compat-build-source.py mkdir -p $(@D)