kbuild: add %.lex.c and %.tab.[ch] to 'targets' automatically

Files generated by if_changed* must be added to 'targets' to include
*.cmd files.  Otherwise, they would be regenerated every time.

The build system automatically adds objects to 'targets' where
appropriate, such as obj-y, extra-y, etc. but does nothing for
intermediate files.  So, each Makefile needs to add them by itself.

There are some common cases where objects are generated by chained
rules.  Lexers and parsers are compiled like follows:

   %.lex.o <- %.lex.c <- %.l
   %.tab.o <- %.tab.c <- %.y

They are common patterns, so it is reasonable to take care of them
in the core Makefile instead of requiring each Makefile to do so.

At this moment, you cannot delete 'target += zconf.lex.c' in the
Kconfig Makefile because zconf.lex.c is included from zconf.tab.c
instead of being compiled separately.  It should be deleted after
Kconfig is more refactored.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Frank Rowand <frowand.list@gmail.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 77cce68c4d63..36f7990c5701 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -538,6 +538,17 @@ $(call multi_depend, $(multi-used-m), .o, -objs -y -m)
 targets += $(multi-used-m)
 targets := $(filter-out $(PHONY), $(targets))
 
+# Add intermediate targets:
+# When building objects with specific suffix patterns, add intermediate
+# targets that the final targets are derived from.
+intermediate_targets = $(foreach sfx, $(2), \
+				$(patsubst %$(strip $(1)),%$(sfx), \
+					$(filter %$(strip $(1)), $(targets))))
+# %.lex.o <- %.lex.c <- %.l
+# %.tab.o <- %.tab.[ch] <- %.y
+targets += $(call intermediate_targets, .lex.o, .lex.c) \
+	   $(call intermediate_targets, .tab.o, .tab.c .tab.h)
+
 # Descending
 # ---------------------------------------------------------------------------