Re: [PATCH v2] Makefile: libfdt: build only the strict necessary

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 4/9/20 6:33 PM, Philippe Mathieu-Daudé wrote:
> Hi Claudio,
> 
> On 4/9/20 2:43 PM, Claudio Fontana wrote:
>> when building dtc/libfdt, we were previously using dtc/Makefile,
>> which tries to build some artifacts that are not needed,
>> and can complain on stderr about the absence of tools that
>> are not required to build just libfdt.
>>
>> Instead, build only the strict necessary to get libfdt.a .
>>
>> Remove the subdir-dtc "compatibility gunk" for recursion,
>> since we are not recursing anymore.
>>
>> Signed-off-by: Claudio Fontana <cfontana@suse.de>
>> ---
>>   Makefile  | 23 +++++++++++++----------
>>   configure |  6 +-----
>>   rules.mak |  2 ++
>>   3 files changed, 16 insertions(+), 15 deletions(-)
>>
>> v1 -> v2:
>>
>> * fix error generated when running UNCHECKED_GOALS without prior 
>> configure,
>>    for example during make docker-image-fedora. Without configure, 
>> DSOSUF is
>>    empty, and the module pattern rule in rules.mak that uses this 
>> variable
>>    can match too much; provide a default in the Makefile to avoid it.
>>
>> * only attempt to build the archive when there is a non-empty list of 
>> objects.
>>    This could be done in general for the %.a: pattern in rules.mak, 
>> but maybe
>>    there are valid reasons to build an empty .a?
>>
>> * removed some intermediate variables that did not add much value
>>    (LIBFDT_srcdir, LIBFDT_archive)
>>
>> Tested locally with 3 VPATH configurations (no-, VPATH, VPATH in src 
>> subdir),
>> and with docker-image-fedora, docker-test-debug@fedora that failed 
>> before.
>>
>> diff --git a/Makefile b/Makefile
>> index 84ef881600..92bc853b5f 100644
>> --- a/Makefile
>> +++ b/Makefile
>> @@ -4,6 +4,10 @@ ifneq ($(words $(subst :, ,$(CURDIR))), 1)
>>     $(error main directory cannot contain spaces nor colons)
>>   endif
>> +# some pattern rules in rules.mak are confused by an empty DSOSUF,
>> +# and UNCHECKED_GOALS for testing (docker-) can run without prior 
>> configure.
>> +DSOSUF ?= ".so"
>> +
>>   # Always point to the root of the build tree (needs GNU make).
>>   BUILD_DIR=$(CURDIR)
>> @@ -526,15 +530,16 @@ $(SOFTMMU_FUZZ_RULES): $(edk2-decompressed)
>>   $(TARGET_DIRS_RULES):
>>       $(call quiet-command,$(MAKE) $(SUBDIR_MAKEFLAGS) -C $(dir $@) 
>> V="$(V)" TARGET_DIR="$(dir $@)" $(notdir $@),)
>> -DTC_MAKE_ARGS=-I$(SRC_PATH)/dtc VPATH=$(SRC_PATH)/dtc -C dtc V="$(V)" 
>> LIBFDT_srcdir=$(SRC_PATH)/dtc/libfdt
>> -DTC_CFLAGS=$(CFLAGS) $(QEMU_CFLAGS)
>> -DTC_CPPFLAGS=-I$(BUILD_DIR)/dtc -I$(SRC_PATH)/dtc 
>> -I$(SRC_PATH)/dtc/libfdt
>> -
>> -.PHONY: dtc/all
>> -dtc/all: .git-submodule-status dtc/libfdt dtc/tests
> 
> I'm getting:
> 
> config-host.mak is out-of-date, running configure
> make: *** No rule to make target 'dtc/all', needed by 'config-host.h'. 
> Stop.
> 
> On second try it works.

FYI same happens when going back (previous this patch applied) but there 
is nothing we can do to prevent that afaik:

config-host.mak is out-of-date, running configure
make: *** No rule to make target 'libfdt', needed by 'config-host.h'.  Stop.

> 
> Instead of alarming users, we could keep this target as a silent no-op, 
> then remove it after some time.
> 
> For the rest, patch looks good, nice cleanup!
> 
> Regards,
> 
> Phil.
> 
>> -    $(call quiet-command,$(MAKE) $(DTC_MAKE_ARGS) 
>> CPPFLAGS="$(DTC_CPPFLAGS)" CFLAGS="$(DTC_CFLAGS)" 
>> LDFLAGS="$(QEMU_LDFLAGS)" ARFLAGS="$(ARFLAGS)" CC="$(CC)" AR="$(AR)" 
>> LD="$(LD)" $(SUBDIR_MAKEFLAGS) libfdt/libfdt.a,)
>> +LIBFDT_objdir = dtc/libfdt
>> +-include $(SRC_PATH)/dtc/libfdt/Makefile.libfdt
>> +LIBFDT_objects = $(addprefix $(LIBFDT_objdir)/, $(LIBFDT_OBJS))
>> +.PHONY: libfdt
>> +libfdt: .git-submodule-status $(LIBFDT_objdir)/libfdt.a
>> +$(LIBFDT_objdir)/libfdt.a: $(LIBFDT_objects)
>> +    $(if $(LIBFDT_objects),$(call quiet-command,rm -f $@ && $(AR) rcs 
>> $@ $^,"AR","$(TARGET_DIR)$@"),)
>> -dtc/%: .git-submodule-status
>> +$(LIBFDT_objects): | $(LIBFDT_objdir)
>> +$(LIBFDT_objdir): .git-submodule-status
>>       @mkdir -p $@
>>   # Overriding CFLAGS causes us to lose defines added in the 
>> sub-makefile.
>> @@ -563,7 +568,6 @@ slirp/all: .git-submodule-status
>>   # Compatibility gunk to keep make working across the rename of targets
>>   # for recursion, to be removed some time after 4.1.
>> -subdir-dtc: dtc/all
>>   subdir-capstone: capstone/all
>>   subdir-slirp: slirp/all
>> @@ -821,7 +825,6 @@ distclean: clean
>>       rm -rf $$d || exit 1 ; \
>>           done
>>       rm -Rf .sdk
>> -    if test -f dtc/version_gen.h; then $(MAKE) $(DTC_MAKE_ARGS) 
>> clean; fi
>>   KEYMAPS=da     en-gb  et  fr     fr-ch  is  lt  no  pt-br  sv \
>>   ar      de     en-us  fi  fr-be  hr     it  lv  nl         pl  
>> ru     th \
>> diff --git a/configure b/configure
>> index 233c671aaa..36f83ffc5a 100755
>> --- a/configure
>> +++ b/configure
>> @@ -4278,10 +4278,6 @@ EOF
>>         if test -d "${source_path}/dtc/libfdt" || test -e 
>> "${source_path}/.git" ; then
>>             fdt=git
>>             mkdir -p dtc
>> -          if [ "$pwd_is_source_path" != "y" ] ; then
>> -              symlink "$source_path/dtc/Makefile" "dtc/Makefile"
>> -              symlink "$source_path/dtc/scripts" "dtc/scripts"
>> -          fi
>>             fdt_cflags="-I\$(SRC_PATH)/dtc/libfdt"
>>             fdt_ldflags="-L\$(BUILD_DIR)/dtc/libfdt"
>>             fdt_libs="$fdt_libs"
>> @@ -8151,7 +8147,7 @@ echo "PIXMAN_CFLAGS=$pixman_cflags" >> 
>> $config_host_mak
>>   echo "PIXMAN_LIBS=$pixman_libs" >> $config_host_mak
>>   if [ "$fdt" = "git" ]; then
>> -  echo "config-host.h: dtc/all" >> $config_host_mak
>> +  echo "config-host.h: libfdt" >> $config_host_mak
>>   fi
>>   if [ "$capstone" = "git" -o "$capstone" = "internal" ]; then
>>     echo "config-host.h: capstone/all" >> $config_host_mak
>> diff --git a/rules.mak b/rules.mak
>> index 694865b63e..61eb474ba4 100644
>> --- a/rules.mak
>> +++ b/rules.mak
>> @@ -105,6 +105,8 @@ LINK = $(call quiet-command, $(LINKPROG) $(CFLAGS) 
>> $(QEMU_LDFLAGS) -o $@ \
>>   DSO_OBJ_CFLAGS := -fPIC -DBUILD_DSO
>>   module-common.o: CFLAGS += $(DSO_OBJ_CFLAGS)
>> +
>> +# Note: DSOSUF must not be empty, or these rules will try to match 
>> too much
>>   %$(DSOSUF): QEMU_LDFLAGS += $(LDFLAGS_SHARED)
>>   %$(DSOSUF): %.mo
>>       $(call LINK,$^)
>>