As various people pointed out, ccache is a great win for people compiling
a lot of kernels. (For info on ccache, see ccache.samba.org)
Unfortunately, when a kernel tree is moved around / cloned / symlinked,
the compiler cache doesn't have many hits, since some header files use
BUG(), which in turn uses __FILE__, which currently includes the absolute
path to the header file.
The appended patch solves this problem by including the headers a relative
path which will not change when the tree is moved.
I'd like to get comments if
o the patch breaks anything for someone and
o it's considered useful enough for inclusion
--Kai
# This is a BitKeeper generated patch for the following project:
# Project Name: Linux kernel tree
# This patch format is intended for GNU patch command version 2.5 or higher.
# This patch includes the following deltas:
# ChangeSet 1.553 -> 1.554
# Rules.make 1.21 -> 1.22
#
# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 02/05/19 kai@tp1.ruhr-uni-bochum.de 1.554
# kbuild: Improve interaction with ccache
#
# Use relativ paths on the command line, thus __FILE__
# in an include file looks like "../../include/linux/foo.h" instead of
# "/home/kai/kernel/v2.5/linux-2.5.make-work/include/linux/foo.h".
#
# The latter is unnecessarily long and in particular changes when
# you move your source tree around, thus causing cache misses with
# ccache.
# --------------------------------------------
#
diff -Nru a/Rules.make b/Rules.make
--- a/Rules.make Sun May 19 18:50:41 2002
+++ b/Rules.make Sun May 19 18:50:41 2002
@@ -49,13 +49,28 @@
MOD_SUB_DIRS := $(sort $(subdir-m) $(both-m))
ALL_SUB_DIRS := $(sort $(subdir-y) $(subdir-m) $(subdir-n) $(subdir-))
+empty :=
+space := $(empty) $(empty)
+
+ifeq ($(TOPDIR),$(CURDIR))
+ RELDIR := ./
+ TOPDIR_REL := ./
+else
+ RELDIR := $(subst $(TOPDIR)/,,$(CURDIR))
+ TOPDIR_REL := $(subst $(space),,$(foreach d,$(subst /, ,$(RELDIR)),../))
+endif
+
#
# Common rules
#
# export_flags will be set to -DEXPORT_SYMBOL for objects in $(export-objs)
-c_flags = $(CFLAGS) $(EXTRA_CFLAGS) $(CFLAGS_$(*F).o) -DKBUILD_BASENAME=$(subst $(comma),_,$(subst -,_,$(*F))) $(export_flags)
+c_flags = $(subst $(TOPDIR)/,$(TOPDIR_REL), \
+ $(CFLAGS) $(EXTRA_CFLAGS) $(CFLAGS_$(*F).o) \
+ -DKBUILD_BASENAME=$(subst $(comma),_,$(subst -,_,$(*F))) \
+ $(export_flags) \
+ )
cmd_cc_s_c = $(CC) $(c_flags) -S $< -o $@
@@ -78,7 +93,9 @@
# the Makefiles to these standard rules. -- rmk, mec
ifdef USE_STANDARD_AS_RULE
-a_flags = $(AFLAGS) $(EXTRA_AFLAGS) $(AFLAGS_$(*F).o)
+a_flags = $(subst $(TOPDIR)/,$(TOPDIR_REL), \
+ $(AFLAGS) $(EXTRA_AFLAGS) $(AFLAGS_$(*F).o) \
+ )
cmd_as_s_S = $(CPP) $(a_flags) $< > $@
@@ -375,5 +392,5 @@
if_changed = $(if $(strip $? \
$(filter-out $($(1)),$(cmd_$@))\
$(filter-out $(cmd_$@),$($(1)))),\
- @echo $($(1)); $($(1)); echo 'cmd_$@ := $($(1))' > .$@.cmd)
+ @echo '$($(1))'; $($(1)); echo 'cmd_$@ := $($(1))' > .$@.cmd)
-
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This archive was generated by hypermail 2b29 : Thu May 23 2002 - 22:00:18 EST