[PATCH 7/7] Makefile: Build with -Werror=date-time if the compilersupports it

[Josh Triplett]

GCC 4.9 and newer have a new warning -Wdate-time, which warns on any use
of __DATE__, __TIME__, or __TIMESTAMP__, which would make the build
non-deterministic.  Now that the kernel does not use any of those
macros, turn on -Werror=date-time if available, to keep it that way.

The kernel already (optionally) records this information at build time
in a single place; other kernel code should not duplicate that.

Signed-off-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
---
 Makefile | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Makefile b/Makefile
index 14d592c..188eea7 100644
--- a/Makefile
+++ b/Makefile
@@ -668,6 +668,9 @@ KBUILD_CFLAGS   += $(call cc-option,-Werror=implicit-int)
 # require functions to have arguments in prototypes, not empty 'int foo()'
 KBUILD_CFLAGS   += $(call cc-option,-Werror=strict-prototypes)
 
+# Prohibit date/time macros, which would make the build non-deterministic
+KBUILD_CFLAGS   += $(call cc-option,-Werror=date-time)
+
 # use the deterministic mode of AR if available
 KBUILD_ARFLAGS := $(call ar-option,D)
 
-- 
1.8.5.2

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