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authorMasahiro Yamada <yamada.masahiro@socionext.com>2017-12-10 01:02:29 +0900
committerMasahiro Yamada <yamada.masahiro@socionext.com>2017-12-16 11:12:53 +0900
commit033dba2ec06c47a9fe1b190bc3281058fb20738d (patch)
treed187e007d9082ab05d482238f9d2e7ddc937c37d /scripts/Makefile.lib
parent73a4f6dbe70a1b93c11e2d1d6ca68f3522daf434 (diff)
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kbuild: prepare to remove C files pre-generated by flex and bison
In Linux build system convention, pre-generated files are version- controlled with a "_shipped" suffix. During the kernel building, they are simply shipped (copied) removing the suffix. This approach can reduce external tool dependency for the kernel build, but it is tedious to manually regenerate such artifacts from developers' point of view. (We need to do "make REGENERATE_PARSERS=1" every time we touch real source files such as *.l, *.y) Some months ago, I sent out RFC patches to run flex, bison, and gperf during the build. In the review and test, Linus noticed gperf-3.1 had changed the lookup function prototype. Then, the use of gperf in kernel was entirely removed by commit bb3290d91695 ("Remove gperf usage from toolchain"). This time, I tested several versions of flex and bison, and I was not hit by any compatibility issue except a flaw in flex-2.6.3; if you generate lexer for dtc and genksyms with flex-2.6.3, you will see "yywrap redefined" warning. This was not intentional, but a bug, fixed by flex-2.6.4. Otherwise, both flex and bison look fairly stable for a long time. This commit prepares some build rules to remove the _shipped files. Also, document minimal requirement for flex and bison. Rationale for the minimal version: The -Wmissing-prototypes option of GCC warns "no previous prototype" for lexers generated by flex-2.5.34 or older, so I chose 2.5.35 as the required version for flex. Flex-2.5.35 was released in 2008. Bison looks more stable. I did not see any problem with bison-2.0, released in 2004. I did not test bison-1.x, but bison-2.0 should be old enough. Tested flex versions: 2.5.35 2.5.36 2.5.37 2.5.39 2.6.0 2.6.1 2.6.2 2.6.3 (*) 2.6.4 (*) flex-2.6.3 causes "yywrap redefined" warning Tested bison versions: 2.0 2.1 2.2 2.3 2.4 2.4.1 2.5.1 2.6 2.6.1 2.6.2 2.6.3 2.6.4 2.6.5 2.7 2.7.1 3.0 3.0.1 3.0.2 3.0.3 3.0.4 Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Diffstat (limited to 'scripts/Makefile.lib')
-rw-r--r--scripts/Makefile.lib20
1 files changed, 17 insertions, 3 deletions
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index ee528e30f80f..0f9ef3fbbaf5 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -186,8 +186,6 @@ $(foreach m, $(notdir $1), \
$(addprefix $(obj)/, $(foreach s, $3, $($(m:%$(strip $2)=%$(s)))))))
endef
-ifdef REGENERATE_PARSERS
-
# LEX
# ---------------------------------------------------------------------------
LEX_PREFIX = $(if $(LEX_PREFIX_${baseprereq}),$(LEX_PREFIX_${baseprereq}),yy)
@@ -195,9 +193,15 @@ LEX_PREFIX = $(if $(LEX_PREFIX_${baseprereq}),$(LEX_PREFIX_${baseprereq}),yy)
quiet_cmd_flex = LEX $@
cmd_flex = $(LEX) -o$@ -L -P $(LEX_PREFIX) $<
+ifdef REGENERATE_PARSERS
.PRECIOUS: $(src)/%.lex.c_shipped
$(src)/%.lex.c_shipped: $(src)/%.l
$(call cmd,flex)
+endif
+
+.PRECIOUS: $(obj)/%.lex.c
+$(filter %.lex.c,$(targets)): $(obj)/%.lex.c: $(src)/%.l FORCE
+ $(call if_changed,flex)
# YACC
# ---------------------------------------------------------------------------
@@ -206,19 +210,29 @@ YACC_PREFIX = $(if $(YACC_PREFIX_${baseprereq}),$(YACC_PREFIX_${baseprereq}),yy)
quiet_cmd_bison = YACC $@
cmd_bison = $(YACC) -o$@ -t -l -p $(YACC_PREFIX) $<
+ifdef REGENERATE_PARSERS
.PRECIOUS: $(src)/%.tab.c_shipped
$(src)/%.tab.c_shipped: $(src)/%.y
$(call cmd,bison)
+endif
+
+.PRECIOUS: $(obj)/%.tab.c
+$(filter %.tab.c,$(targets)): $(obj)/%.tab.c: $(src)/%.y FORCE
+ $(call if_changed,bison)
quiet_cmd_bison_h = YACC $@
cmd_bison_h = bison -o/dev/null --defines=$@ -t -l -p $(YACC_PREFIX) $<
+ifdef REGENERATE_PARSERS
.PRECIOUS: $(src)/%.tab.h_shipped
$(src)/%.tab.h_shipped: $(src)/%.y
$(call cmd,bison_h)
-
endif
+.PRECIOUS: $(obj)/%.tab.h
+$(filter %.tab.h,$(targets)): $(obj)/%.tab.h: $(src)/%.y FORCE
+ $(call if_changed,bison_h)
+
# Shipped files
# ===========================================================================