[U-Boot] [PATCH] Reproducible U-Boot build support, using SOURCE_DATE_EPOCH

[Paul Kocialkowski <contact@paulk.fr>]

Le lundi 20 juillet 2015 ? 07:45 -0700, Vagrant Cascadian a ?crit :
> On 2015-07-20, Paul Kocialkowski wrote:
> > In order to achieve reproducible builds in U-Boot, timestamps that are defined
> > at build-time have to be somewhat eliminated. The SOURCE_DATE_EPOCH environment
> > variable allows setting a fixed value for those timestamps.
> ...
> > diff --git a/Makefile b/Makefile
> > index 37cc4c3..71aeac7 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -1231,9 +1231,10 @@ define filechk_version.h
> >  endef
> >  
> >  define filechk_timestamp.h
> > -	(LC_ALL=C date +'#define U_BOOT_DATE "%b %d %C%y"'; \
> > -	LC_ALL=C date +'#define U_BOOT_TIME "%T"'; \
> > -	LC_ALL=C date +'#define U_BOOT_TZ "%z"')
> > +	(SOURCE_DATE="$${SOURCE_DATE_EPOCH:+@$$SOURCE_DATE_EPOCH}"; \
> > +	LC_ALL=C date -u -d "$${SOURCE_DATE:-now}" +'#define U_BOOT_DATE "%b %d %C%y"'; \
> > +	LC_ALL=C date -u -d "$${SOURCE_DATE:-now}" +'#define U_BOOT_TIME "%T"'; \
> > +	LC_ALL=C date -u -d "$${SOURCE_DATE:-now}" +'#define U_BOOT_TZ "%z"' )
> >  endef
> >  
> >  $(version_h): include/config/uboot.release FORCE
> 
> This does effectively hard-code U_BOOT_TZ to UTC; may as well not call
> date for setting U_BOOT_TZ. Or conditionally set it to UTC only when
> SOURCE_DATE_EPOCH is set?

That's true, but I like how consistent those commands look. Either way,
it's not a dramatic overhead, but I agree it's slightly confusing. If
you really think it's worth it, I could simply hardcode UTC in v2. Just
let me know!

I'd rather keep everything in one call (doing UTC only when
SOURCE_DATE_EPOCH is set looks overkill).

> Any reason not to use the longhand options for date, e.g. --utc and
> --date ? They're more readable; are they less portable?

I don't think they are, but the short options look fine to me. Note that
out of those lines, two still fit in a 80 chars column. Adding long
options would make readability harder in that regard.

As far as I'm concerned, it's fine as it is, but if you really think it
would be a worthwhile addition to use the long options, let me know.
Please do check that it doesn't break portability, too.

Thanks for the review!

-- 
Paul Kocialkowski, Replicant developer

Replicant is a fully free Android distribution running on several
devices, a free software mobile operating system putting the emphasis on
freedom and privacy/security.

Website: http://www.replicant.us/
Blog: http://blog.replicant.us/
Wiki/tracker/forums: http://redmine.replicant.us/
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