Re: Automatic dependency resolution on generated python file

[Michal Marek <mmarek@suse.com>]

On 2016-05-24 01:02, Kieran Bingham wrote:
> Hi Kbuild / Michal,
> 
> I've been working through a problem that Jan has reported whereby if we
> modify a file included by our template  for constants.py, the generated
> file is not rebuilt.
> 
> The rule/cmd [0] to generate the python constants is
> cmd_gen_constants_py which uses the $(CPP) with $(c_flags) to create the
> output.
> 
> One benefit of this is that it already creates the $(depfile) through
> the addition of the flags provided by $(c_flags), however as yet it
> would seem that my efforts to understand how the $(depfile) gets
> included have failed.
> 
> From what I can tell, the $(call if_changed...) rule is generating my
> targets .constants.py.cmd, but the .d file is not being utilised.
> 
> By swapping $(call if_changed, ) to $(call if_changed_dep,...) I can see
> that my .constants.py.cmd [1] file now has (apparently) correct
> dependency rules being generated. However they still don't take actual
> effect. If I 'touch/modify' one of the files I have added to the
> #includes, then my target is not rebuilt (I have added
> include/linux/kieran.h for testing this specifically without rebuilding
> all other objects)

Hi Kieran,

sorry for the late reply. In case this is still relevant: For
if_changed/if_changed_dep to work, you must list the target in the
$(targets) list (without the $(obj) prefix) and add FORCE as a
prerequisite of the rule.

Michal