[PATCH] nscd_stat.c: make the build reproducible

[Aurelien Jarno <aurelien@aurel32.net>]

nscd_stat.c uses the __DATE__ and __TIME__ macros to make sure the
client and the server use the same format. This prevents reproducible
builds and fails to build with -Werror=date-time. In addition another
build of the same file a bit later does not necessary imply a change
in the format.

Instead compute a checksum of the file in the Makefile and pass it to
the preprocessor with the -D option. Use the md5sum command limited to
20 characters to avoid changing the structure size.

Changelog:
	* math/nscd (CPPFLAGS-nscd_stat.c): Append -DNSCD_STAT_C_CHECKSUM=...
	with the checksum of nscd_stat.c computed with md5sum.
	* nscd/nscd_stat.c (compilation): Use NSCD_STAT_C_CHECKSUM instead of
	__DATE__ " " __TIME__.
---
 ChangeLog        | 7 +++++++
 nscd/Makefile    | 4 ++++
 nscd/nscd_stat.c | 2 +-
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/ChangeLog b/ChangeLog
index 289d578..8f0b24f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2016-03-08  Aurelien Jarno  <aurelien@aurel32.net>
+
+	* math/nscd (CPPFLAGS-nscd_stat.c): Append -DNSCD_STAT_C_CHECKSUM=...
+	with the checksum of nscd_stat.c computed with md5sum.
+	* nscd/nscd_stat.c (compilation): Use NSCD_STAT_C_CHECKSUM instead of
+	__DATE__ " " __TIME__.
+
 2016-03-08  H.J. Lu  <hongjiu.lu@intel.com>
 
 	[BZ #19783]
diff --git a/nscd/Makefile b/nscd/Makefile
index 50bad32..2678c6b 100644
--- a/nscd/Makefile
+++ b/nscd/Makefile
@@ -90,6 +90,10 @@ ifeq (yesyes,$(have-fpie)$(build-shared))
 LDFLAGS-nscd = -Wl,-z,now
 endif
 
+# Compute a checksum of the file to verify that the sender and the
+# receiver are using the same format.
+CPPFLAGS-nscd_stat.c += -DNSCD_STAT_C_CHECKSUM='"$(shell md5sum $< | cut -c1-20)"'
+
 # Set libof-nscd.
 cpp-srcs-left := $(nscd-modules)
 lib := nscd
diff --git a/nscd/nscd_stat.c b/nscd/nscd_stat.c
index f34c352..fa294ca 100644
--- a/nscd/nscd_stat.c
+++ b/nscd/nscd_stat.c
@@ -37,7 +37,7 @@
 
 
 /* We use this to make sure the receiver is the same.  */
-static const char compilation[21] = __DATE__ " " __TIME__;
+static const char compilation[21] = NSCD_STAT_C_CHECKSUM;
 
 /* Statistic data for one database.  */
 struct dbstat
-- 
2.7.0