Re: [PATCH] coverage: filter out lib{fdt,elf}-temp.o

[Jan Beulich <jbeulich@xxxxxxxx>]

On 22.01.2024 11:54, Anthony PERARD wrote:
> On Mon, Jan 22, 2024 at 11:04:41AM +0100, Jan Beulich wrote:
>> On 19.01.2024 16:25, Anthony PERARD wrote:
>>> On Fri, Jan 19, 2024 at 09:43:30AM +0100, Michal Orzel wrote:
>>>> Is my understanding correct that by switching from extra-y to targets we 
>>>> are preventing these objects to
>>>> appear in non-init-objects (and thus having COV_FLAGS appended) while 
>>>> retaining the proper if_changed behavior?
>>>>
>>>> According to docs/misc/xen-makefiles/makefiles.rst:
>>>> Any target that utilises if_changed must be listed in $(targets),
>>>> otherwise the command line check will fail, and the target will
>>>> always be built.
>>>
>>> Indeed, and $(extra-y) is added to $(targets) via
>>> $(targets-for-builtin).
>>>
>>> While switching from $(extra-y) to $(targets) prevents the objects from
>>> been added to $(non-init-objets), it doesn't matter because "libelf.o"
>>> is in that variable, so $(COV_FLAGS) is added to $(_c_flags) and its
>>> value is used in all the prerequisites of "libelf.o" which includes
>>> "libelf-temp.o" and for example "libelf-dominfo.o". So the only thing
>>> preventing $(COV_FLAGS) from been added when building "libelf-tools.o"
>>> for example is that we set `COV_FLAGS:=` for "libelf.o".
>>
>> Yet doesn't that (again) mean things should actually work as-is, [...]
> 
> No, because I've explain how it should work, in the hypothetical world
> where we have `targets += libelf-temp.o $(libelf-objs)`.

Yes and no: Why would the COV_FLAGS propagation to prereqs not work today?
Whether libelf-*.o are prereqs to libelf-temp.o or to libelf.o shouldn't
matter, nor should it matter whether libelf-temp.o or libelf.o (or both)
are listed in $(targets). As soon as either libelf-temp.o or libelf.o has
COV_FLAGS overridden (to empty), libelf-*.o ought to be built with empty
COV_FLAGS. What am I missing?

Jan