[Buildroot] [PATCH 2/7] pkg-infra: assign BR_NO_CHECK_HASH_FOR so it is recursively-expanded
Yann E. MORIN
yann.morin.1998 at free.fr
Fri May 1 15:26:48 UTC 2015
arnout, All,
On 2015-05-01 15:07 +0200, Arnout Vandecappelle spake thusly:
> On 29/04/15 00:39, Yann E. MORIN wrote:
> > Currently, assigning to BR_NO_CHECK_HASH_FOR in conditionals, but
> > referencing vairaible assigned to later, fails. Here's a failing
> variable
>
> > test-case, which is the reduced test-case of how we handle
> > BR_NO_CHECK_HASH_FOR for now:
> >
> > export FOO
> >
> > ifeq ($(BAR_V),)
> > BAR_V=1
> > else
> > FOO += $(BAR_S)
> > endif
>
> I think the test case is too complicated - in fact the conditional construct
> has nothing to do with it.
Yup, right, I know. However, I wanted a reduced test-case that still
ressembled our current code base.
> The culprit is appending to it, which means we never
> explicitly set it to recursively expanded. Exported variables that are not
> defined explicitly for some reason default to be immediately expanded rather
> than recursively.
Exactly. However, there's nothing like so explained in the make manual.
> export FOO
> FOO += $(BAR)
> $(warning FOO='$(FOO)' BAR='$(BAR)')
> BAR = BAR
> $(warning FOO='$(FOO)' BAR='$(BAR)')
> default:
>
> Will give
>
> /tmp/Makefile:3: FOO=' ' BAR=''
> /tmp/Makefile:5: FOO=' ' BAR='BAR'
>
> while explicitly setting FOO to be recursively expanded:
>
> export FOO =
>
> will give
>
> /tmp/Makefile:3: FOO=' ' BAR=''
> /tmp/Makefile:5: FOO=' BAR' BAR='BAR'
Do you prefere I use your even-more-simplified test-case, or may I keep
the reduced test-case I provided that ressemble our current code-path?
> >
> > BAR_S = bar-$(BAR_V).tar
> >
> > all:
> > @echo "BAR_S=\"$(BAR_S)\""
> > @$(SHELL) -c 'echo "FOO=\"$${FOO}\""'
> >
> > Run it with:
> >
> > $ make
> > BAR_S="bar-1.tar"
> > FOO=""
> > $ make BAR_V=2
> > BAR_S="bar-2.tar"
> > FOO=" "
> >
> > Now, change the firstline to read:
> >
> > export FOO =
> >
> > And we now get:
> >
> > $ make
> > BAR_S="bar-1.tar"
> > FOO=""
> > $ make BAR_V=2
> > BAR_S="bar-2.tar"
> > FOO=" bar-2.tar"
> >
> > This new behaviour will be needed later for Xenomai, which handles the
> > version string in an unusual way.
> >
> > (Note how there's a leading space in both cases? In Buildroot, we do not
> > care that extra space, it is simply ignored).
>
> The leading space is there because += always inserts a space, even if the
> variable was empty before.
Yes, I know. I'll ditch that comment.
> > Signed-off-by: "Yann E. MORIN" <yann.morin.1998 at free.fr>
> > Cc: Arnout Vandecappelle <arnout at mind.be>
> > Cc: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
> > ---
> > package/pkg-download.mk | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/package/pkg-download.mk b/package/pkg-download.mk
> > index a38062e..f0651db 100644
> > --- a/package/pkg-download.mk
> > +++ b/package/pkg-download.mk
> > @@ -56,7 +56,9 @@ domainseparator = $(if $(1),$(1),/)
> > github = https://github.com/$(1)/$(2)/archive/$(3)
> >
> > # Expressly do not check hashes for those files
> > -export BR_NO_CHECK_HASH_FOR
> > +# It needs to be assigned so as to be a recursively-expanded variable, and
> > +# so that it can be assigned inside conditionals.
>
> # Exported variables default to immediately expanded,
I would avoid stating that. That's the behaviour we observed, but
nothing is said about that in the make manual. If a future version of
make changes that behaviour, the comment would be wrong.
However, I'll ditch the comment about conditionals.
> # but we need it to be
> # recursively-epxanded, so explicitly define it.
>
>
> With all that,
>
> Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout at mind.be>
Regards,
Yann E. MORIN.
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