Re: [XEN PATCH v4 06/18] xen/build: have the root Makefile generates the CFLAGS

[Jan Beulich <jbeulich@xxxxxxxx>]

On 15.04.2020 16:10, Anthony PERARD wrote:
> On Wed, Apr 08, 2020 at 01:50:33PM +0200, Jan Beulich wrote:
>> On 31.03.2020 12:30, Anthony PERARD wrote:
>>>  # Always build obj-bin files as binary even if they come from C source. 
>>> -$(obj-bin-y): CFLAGS := $(filter-out -flto,$(CFLAGS))
>>> +# FIXME LTO broken, but we would need a different way to filter -flto out
>>> +# $(obj-bin-y): CFLAGS := $(filter-out -flto,$(CFLAGS))
>>
>> While you mention this in the description, I'm still not overly
>> happy with it getting commented out. What's wrong with making the
>> construct simply act on c_flags?
> 
> It doesn't work.
> 
> I tried
>     $(obj-bin-y): c_flags := $(filter-out -flto,$(c_flags))
> but the $@ expansion was empty.

Hmm, yes, presumably because of having to use :=. But the old
code gives the appearance of having worked despite this fact.

> I guess we could do:
>     $(obj-bin-y): XEN_CFLAGS := $(filter-out -flto,$(XEN_CFLAGS))
> that's probably enough for now. Even if we can't test it properly.

If -flto gets added to XEN_CFLAGS (not c_flags) - why not?

Jan