[Reproducible-builds] [RFC PATCH v2] Makefile: search for GNU date

[Paul Kocialkowski]

Le jeudi 27 août 2015 à 11:30 +0200, Andreas Bießmann a écrit :
> The SOURCE_DATE_EPOCH mechanism for reproducible builds require some date
> with -u and -d switch to print the date string of another time. In other
> words it requires some date that behaves like the GNU date.
> 
> Respect this and search a working date, error on no working version.

Looks good to me, except one nitpick, see below.

> Signed-off-by: Andreas Bießmann <andreas.devel at googlemail.com>
> ---
> This commit tries to figure out if we have a date variant
> available that supports the '-u' and '-d "@0"' switches.
> It errors on non-working variants of date.
>
> To respect *BSD host systems search for gdate and date.gnu. Those pre- and
> suffixes are widespread used for the GNU variant of a tool also avialable on
> *BSD systems.

Fair enough then, that's fine with me.

> The result is:
> 
> ---8<---
> abiessmann at punisher % PATH=$ARMv5_PATH:$PATH CROSS_COMPILE=arm-v5te-linux-gnueabi- make O=/tmp/picosam ARCH=arm include/generated/timestamp_autogenerated.h
> make[1]: Entering directory '/tmp/picosam'
>   CHK     include/generated/timestamp_autogenerated.h
>   UPD     include/generated/timestamp_autogenerated.h
> make[1]: Leaving directory '/tmp/picosam'
> abiessmann at punisher % PATH=$ARMv5_PATH:$PATH CROSS_COMPILE=arm-v5te-linux-gnueabi- make O=/tmp/picosam SOURCE_DATE_EPOCH="0" ARCH=arm include/generated/timestamp_autogenerated.h
> make[1]: Entering directory '/tmp/picosam'
> /home/abiessmann/src/u-boot/Makefile:1304: *** "Your gdate/date.gnu/date does not support the '-u' and '-d' switches like GNU date does!".  Stop.
> make[1]: Leaving directory '/tmp/picosam'
> Makefile:146: recipe for target 'sub-make' failed
> make: *** [sub-make] Error 2
> --->8---
> 
> It applies on top of http://patchwork.ozlabs.org/patch/506856/ (Makefile: Use correct timezone for U_BOOT_TZ).
> 
> Changes in v2:
> * check for '-u' and '-d "@0"' switch rather than for the GNU variant
> 
>  Makefile | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index b9b2375..b797e38 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -346,6 +346,10 @@ PERL		= perl
>  PYTHON		= python
>  DTC		= dtc
>  CHECK		= sparse
> +DATE	       := $(foreach date,gdate date.gnu date, \
> +		    $(shell _date=`which $(date)`; \
> +		      $${_date} -u -d "@0" >/dev/null 2>&1; \
> +		      test $$? -eq 0 && echo $${_date}))

First, I don't understand why you need to call date with the full path:
if which can find it, then calling the binary without its full path
should do just as well, right?

Then, correct me if I'm wrong, but calling test and using && is
overkill, you could simply do: $${_date} -u -d "@0" >/dev/null 2>&1 &&
echo $${_date}

So in the end, the whole line would look like:

DATE	       := $(foreach date,gdate date.gnu date, \
		    $($${date} -u -d "@0" >/dev/null 2>&1 \
		      && echo $${date}))

Let me know what you think (and please test it as well).

>  CHECKFLAGS     := -D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__ \
>  		  -Wbitwise -Wno-return-void -D__CHECK_ENDIAN__ $(CF)
> @@ -1281,9 +1285,9 @@ endef
>  define filechk_timestamp.h
>  	(if test -n "$${SOURCE_DATE_EPOCH}"; then \
>  		SOURCE_DATE="@$${SOURCE_DATE_EPOCH}"; \
> -		LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_DATE "%b %d %C%y"'; \
> -		LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TIME "%T"'; \
> -		LC_ALL=C date -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TZ "%z"'; \
> +		LC_ALL=C $(DATE) -u -d "$${SOURCE_DATE}" +'#define U_BOOT_DATE "%b %d %C%y"'; \
> +		LC_ALL=C $(DATE) -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TIME "%T"'; \
> +		LC_ALL=C $(DATE) -u -d "$${SOURCE_DATE}" +'#define U_BOOT_TZ "%z"'; \
>  	else \
>  		LC_ALL=C date +'#define U_BOOT_DATE "%b %d %C%y"'; \
>  		LC_ALL=C date +'#define U_BOOT_TIME "%T"'; \
> @@ -1295,6 +1299,11 @@ $(version_h): include/config/uboot.release FORCE
>  	$(call filechk,version.h)
>  
>  $(timestamp_h): $(srctree)/Makefile FORCE
> +ifneq ($(strip $(SOURCE_DATE_EPOCH)),)
> +ifeq ($(strip $(DATE)),)
> +	$(error "Your gdate/date.gnu/date does not support the '-u' and '-d' switches like GNU date does!")
> +endif
> +endif
>  	$(call filechk,timestamp.h)
>  
>  # ---------------------------------------------------------------------------

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