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authorJean-Philippe Brucker <jean-philippe@linaro.org>2020-03-12 17:19:45 +0100
committerDenys Vlasenko <vda.linux@googlemail.com>2020-04-29 14:52:19 +0200
commited8af51b600fd16d22c6663a241547c3a9d7f2b4 (patch)
treecefe5aea5aaf30a1d96de97184aba405825ea509 /scripts/Kbuild.include
parentb9943741c26e1e597edc142066f428540d1f1207 (diff)
downloadbusybox-ed8af51b600fd16d22c6663a241547c3a9d7f2b4.tar.gz
build system: remove KBUILD_STR()
When using GNU Make >=4.3, the KBUILD_STR() definition interferes badly with dependency checks during build, and forces a complete rebuild every time Make runs. In if_changed_rule, Kconfig checks if the command used to build a file has changed since last execution. The previous command is stored in the generated .<file>.o.cmd file. For example applets/.applets.o.cmd defines a "cmd_applets/applets.o" variable: cmd_applets/applets.o := gcc ... -D"KBUILD_STR(s)=#s" ... Here the '#' should be escaped with a backslash, otherwise GNU Make interprets it as starting a comment, and ignore the rest of the variable. As a result of this truncation, the previous command doesn't equal the new command and Make rebuilds each target. The problem started to appear when GNU Make 4.3 (released January 2020), introduced a backward-incompatible fix to macros containing a '#'. While the above use of '#', a simple Make variable, still needs to be escaped, a '#' within a function invocation doesn't need to be escaped anymore. As Martin Dorey explained on the GNU Make discussion [1], the above declaration is generated from make-cmd, defined as: make-cmd = $(subst \#,\\\#,$(subst $$,$$$$,$(call escsq,$(cmd_$(1)))) Since GNU Make 4.3, the first argument of subst should not have a backslash. make-cmd now looks for literally \# and doesn't find it, and as a result doesn't add the backslash when generating .o.cmd files. [1] http://savannah.gnu.org/bugs/?20513 We could fix it by changing make-cmd to "$(subst #,\#,...)", but to avoid compatibility headaches, simply get rid of the KBUILD_STR definition, as done in Linux by b42841b7bb62 ("kbuild: Get rid of KBUILD_STR"). Quote the string arguments directly rather than asking the preprocessor to quote them. Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Diffstat (limited to 'scripts/Kbuild.include')
-rw-r--r--scripts/Kbuild.include1
1 files changed, 1 insertions, 0 deletions
diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index 6ec1809a2..5b4db5c2c 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -4,6 +4,7 @@
# Convinient variables
comma := ,
squote := '
+quote := "
empty :=
space := $(empty) $(empty)