#ifdef reduction infrastructure, based on an argument between Shaun Jackman,

Rob Landley, and others.

Currently CONFIG options are defined or undefined, so we chop out code with
#ifdefs, ala:
#ifdef CONFIG_THING
  stuff();
#endif

This creates a new header file, bb_config.h, which sets the CONFIG entry to 1
or 0, and lets us do:

  if(CONFIG_THING) stuff();

And let the compiler do dead code elimination to get rid of it.  (Note: #ifdef
will still work because for the 1 case it's a static const int, not a #define.)

1 files changed, 7 insertions, 2 deletions

diff --git a/Makefile b/Makefile
index d205bb1b6..807ab5058 100644
--- a/Makefile
+++ b/Makefile
@@ -122,7 +122,7 @@ $(ALL_MAKEFILES): %/Makefile: $(top_srcdir)/%/Makefile
 include $(patsubst %,%/Makefile.in, $(SRC_DIRS))
 -include $(top_builddir)/.depend
 
-busybox: $(ALL_MAKEFILES) .depend include/config.h $(libraries-y)
+busybox: $(ALL_MAKEFILES) .depend include/bb_config.h $(libraries-y)
         $(CC) $(LDFLAGS) -o $@ -Wl,--start-group $(libraries-y) $(LIBRARIES) -Wl,--end-group
         $(STRIPCMD) $@
 
@@ -212,6 +212,11 @@ include/config.h: .config
         fi;
         @$(top_builddir)/scripts/config/conf -o $(CONFIG_CONFIG_IN)
 
+include/bb_config.h: include/config.h
+        echo "#ifndef AUTOCONF_INCLUDED" > $@
+        sed -e 's/#undef \(.*\)/static const int \1 = 0;/' < $< >> $@
+        echo "#endif" >> $@
+
 finished2:
         @echo
         @echo Finished installing...
@@ -279,7 +284,7 @@ clean:
 
 distclean: clean
         - rm -f scripts/split-include scripts/mkdep
-        - rm -rf include/config include/config.h
+        - rm -rf include/config include/config.h include/bb_config.h
         - find . -name .depend -exec rm -f {} \;
         rm -f .config .config.old .config.cmd
         - $(MAKE) -C scripts/config clean