Re: [PATCH v2 1/4] build: add make macro for making file from file.in

[Jürgen Groß <jgross@xxxxxxxx>]

On 14.11.25 12:42, Andrew Cooper wrote:
> On 14/11/2025 11:32 am, Juergen Gross wrote:
> > diff --git a/Config.mk b/Config.mk
> > index e1556dfbfa..d21d67945a 100644
> > --- a/Config.mk
> > +++ b/Config.mk
> > @@ -159,6 +159,19 @@ define move-if-changed
> >         if ! cmp -s $(1) $(2); then mv -f $(1) $(2); else rm -f $(1); fi
> >   endef
> >   
> > +PATH_FILES := Paths
> > +INC_FILES := $(foreach f, $(PATH_FILES), $(XEN_ROOT)/config/$(f).mk)
> > +
> > +include $(INC_FILES)
> > +
> > +BUILD_MAKE_VARS := $(foreach f, $(PATH_FILES), $(shell awk '$$2 == ":=" { 
> > print $$1; }' $(XEN_ROOT)/config/$(f).mk.in))
> > +
> > +# Replace @xxx@ markers in $(1).in with $(xxx) variable contents, write to $(1)
> > +define apply-build-vars
> > + $(1): $(1).in
> > +       sed $$(foreach v, $$(BUILD_MAKE_VARS), -e 's#@$$(v)@#$$($$(v))#g') <$$< 
> > >$$@
> > +endef
> Shouldn't this write to a tmp file, and use move-if-changed?  Most of
> the time the markers won't have changed, and we'll want to short circuit
> dependent rules.
I can see this being an advantage when e.g. generating header files, as
those being generated again would potentially cause lots of rebuilds.

In this case I can hardly see any case where make wouldn't do the right
thing already. Either the *.in file is newer than the generated file due
to a git update or a manual edit, so make will regenerate the target (and
this is what we want), or the *.in file hasn't changed, so make won't
regenerate the file as it is newer than the *.in file already.

Or did I miss some aspect?

What IS needed is probably a dependency on $(PATH_FILES) in case someone
did a new ./configure call without a make distclean.


Juergen

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