Re: [Qemu-devel] [PATCH] make: automatically include dependencies in recursive subdir rules

[Andreas Färber]

Am 17.06.2012 17:20, schrieb Blue Swirl:
> On Sun, Jun 17, 2012 at 2:57 PM, Anthony Liguori <address@hidden> wrote:
>> I think I understand enough of what's going on in these rules to ensure this 
>> is
>> right.  But I could certainly use a second or third opinion...
>>
>> Signed-off-by: Anthony Liguori <address@hidden>
>> ---
>>  Makefile  |    4 ++--
>>  rules.mak |    1 +
>>  2 files changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/Makefile b/Makefile
>> index cce45fb..593bd9b 100644
>> --- a/Makefile
>> +++ b/Makefile
>> @@ -405,5 +405,5 @@ tar:
>>  Makefile: $(GENERATED_HEADERS)
>>
>>  # Include automatically generated dependency files
>> --include $(wildcard *.d audio/*.d slirp/*.d block/*.d net/*.d ui/*.d 
>> qapi/*.d)
>> --include $(wildcard qga/*.d hw/*.d hw/usb/*.d qom/*.d)
>> +# All subdir dependencies come automatically from our recursive subdir rules
>> +-include $(wildcard *.d)
> 
> include $(wildcard *.d */*.d */*/*.d */*/*/*.d)
> ?

No. Due to our directory structure not all dependency files apply to
Makefile.

Anyway, the problem is that any such "fixed" wildcard expression still
silently fails when another level gets added. We've seen that simply no
one notices, and the resulting errors are weird and non-telling.
Therefore it was suggested to have some automatic way of deducing the
dependency files from .o files. (See the "Makefile: Fix dependencies for
QOM" thread.)

>> diff --git a/rules.mak b/rules.mak
>> index 4bc5e52..8c5ef95 100644
>> --- a/rules.mak
>> +++ b/rules.mak
>> @@ -94,6 +94,7 @@ define unnest-dir
>>  $(foreach var,$(nested-vars),$(call push-var,$(var),$1/))
>>  $(eval obj := $(obj)/$1)
>>  $(eval include $(SRC_PATH)/$1/Makefile.objs)
>> +$(eval -include $(wildcard $(SRC_PATH)/$1/*.d))
> 
> This assumes a build in the source directory, s/SRC_PATH/BUILD_DIR/.

I've tested with just
+$(eval -include $(wildcard $1/*.d))
and did
$ touch include/qemu/object.h

>From what I see, using Anthony's original patch plus the modification
above (not the other ones), {i386,x86_64}-softmmu/hw/kvm/apic.o is still
not getting rebuilt despite its included hw/apic_internal.h depending on
sysbus.h -> qdev.h -> qemu/object.h.

They're being added via obj-$(CONFIG_KVM) += kvm/filename.o, not via the
recursive directory rule, so are not caught by Anthony's rule.

Maybe fix by some explicit Makefile-specific rule such as this?

diff --git a/hw/i386/Makefile.objs b/hw/i386/Makefile.objs
index d43f1df..1e8423a 100644
--- a/hw/i386/Makefile.objs
+++ b/hw/i386/Makefile.objs
@@ -11,3 +11,5 @@ obj-$(CONFIG_KVM) += kvm/clock.o kvm/apic.o
kvm/i8259.o kvm/ioapic.o kvm/i8254.o
 obj-$(CONFIG_SPICE) += qxl.o qxl-logger.o qxl-render.o

 obj-y := $(addprefix ../,$(obj-y))
+
+-include $(wildcard ../kvm/*.d)

Andreas

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