Re: [Qemu-devel] [PATCH] qapi: Reduce Makefile boilerplate

[Eric Blake <eblake@redhat.com>]

On 11/15/18 4:37 PM, Eric Blake wrote:
> I'm trying to do the same thing to Makefile.objs, but when I use:
> 
> common-obj-y += $(QAPI_MODULES:%=qapi/qapi-commands-%.o)
> 
> or the longer $(patsubst %,qapi,qapi-commands-%.o,$(QAPI_MODULES))
> 
> both before and after the change, 'make print-common-obj-y | grep qapi' 
> returns identical content, but after the change, the linker fails with:
> 

> 
> So something about variable expansions is NOT playing nicely with our
> 
> dummy := $(call unnest-vars,, \
>                  stub-obj-y \
>                  chardev-obj-y \
> ...
>                  common-obj-y \

Aha - the problem is that $(QAPI_MODULES) is empty at the time 
unnest-vars tries to slurp in Makefile.objs, while it was non-empty at 
the time that Makefile directly includes it. Moving the definition of 
QAPI_MODULES into Makefile.objs solves that. v2 coming up.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org