vserver 1.9.5.x5

[linux-2.6.git] / scripts / Makefile.lib

diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 3a7663b..6e75ced 100644 (file)
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -232,3 +232,30 @@ descend =$(Q)$(MAKE) -f $(if $(KBUILD_SRC),$(srctree)/)scripts/Makefile.build ob
 # Usage:
 # $(Q)$(MAKE) $(build)=dir
 build := -f $(if $(KBUILD_SRC),$(srctree)/)scripts/Makefile.build obj
+
+# filechk is used to check if the content of a generated file is updated.
+# Sample usage:
+# define filechk_sample
+#      echo $KERNELRELEASE
+# endef
+# version.h : Makefile
+#      $(call filechk,sample)
+# The rule defined shall write to stdout the content of the new file.
+# The existing file will be compared with the new one.
+# - If no file exist it is created
+# - If the content differ the new file is used
+# - If they are equal no change, and no timestamp update
+
+define filechk
+       $(Q)set -e;                             \
+       echo '  CHK     $@';                    \
+       mkdir -p $(dir $@);                     \
+       $(filechk_$(1)) $(2) > $@.tmp;          \
+       if [ -r $@ ] && cmp -s $@ $@.tmp; then  \
+               rm -f $@.tmp;                   \
+       else                                    \
+               echo '  UPD     $@';            \
+               mv -f $@.tmp $@;                \
+       fi
+endef
+