build system: remove KBUILD_STR()

2020-04-29T12:52:19+00:00

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 ..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 Signed-off-by: Denys Vlasenko

- need to pass the PATH down to the gcc-version check to be able to find the correct cc.

2007-06-25T10:41:01+00:00

Fixes make PATH="$CROSS_BIN:$PATH" CROSS_COMPILE=foo- like invocations that previously failed to resolve since the information about the path set by the user was lost.

- add hostcc-option checker

2007-01-23T11:44:14+00:00

Trailing whitespace removal over entire tree

2007-01-11T17:20:00+00:00

build system overhaul

2006-10-05T10:17:08+00:00

forks/busybox/scripts/Kbuild.include, branch master

build system: remove KBUILD_STR()

- need to pass the PATH down to the gcc-version check to be able to find the correct cc.

- add hostcc-option checker

Trailing whitespace removal over entire tree

build system overhaul