user hostile gobbledygook in top level Makefile

["Zack Weinberg" <zackw at stanford dot edu>]

So I'm trying to figure out why I can't override BOOT_CFLAGS on the
command line from the top level - not in the gcc subdirectory - and I
see this in the top Makefile.in:

EXTRA_GCC_FLAGS = \
	'AR=$(AR)' \
	'AS=$(AS)' \
	'CC=$(CC)' \
	'CXX=$(CXX)' \
	'DLLTOOL=$$(DLLTOOL_FOR_TARGET)' \
	'HOST_CC=$(CC_FOR_BUILD)' \
	'HOST_PREFIX=$(HOST_PREFIX)' \
	'HOST_PREFIX_1=$(HOST_PREFIX_1)' \
	'NM=$(NM)' \
	'RANLIB=$(RANLIB)' \
	'WINDRES=$$(WINDRES_FOR_TARGET)' \
	"GCC_FOR_TARGET=$(GCC_FOR_TARGET)" \
	"`echo 'LANGUAGES=$(LANGUAGES)' | sed -e s/.*=$$/XFOO=/`" \
	"`echo 'STMP_FIXPROTO=$(STMP_FIXPROTO)' | sed -e s/.*=$$/XFOO=/`" \
	"`echo 'LIMITS_H_TEST=$(LIMITS_H_TEST)' | sed -e s/.*=$$/XFOO=/`" \
	"`echo 'LIBGCC1_TEST=$(LIBGCC1_TEST)' | sed -e s/.*=$$/XFOO=/`" \
	"`echo 'LIBGCC2_CFLAGS=$(LIBGCC2_CFLAGS)' | sed -e s/.*=$$/XFOO=/`" \
	"`echo 'LIBGCC2_DEBUG_CFLAGS=$(LIBGCC2_DEBUG_CFLAGS)' | sed -e s/.*=$$/XFOO=/`" \
	"`echo 'LIBGCC2_INCLUDES=$(LIBGCC2_INCLUDES)' | sed -e s/.*=$$/XFOO=/`" \
	"`echo 'ENQUIRE=$(ENQUIRE)' | sed -e s/.*=$$/XFOO=/`" \
	"`echo 'BOOT_CFLAGS=$(BOOT_CFLAGS)' | sed -e s/.*=$$/XFOO=/`"

Now, unless I am sorely confused, the effect of those echo | sed
commands is to convert "BOOT_CFLAGS=-fwhatever" into
"XFOO=-fwhatever", which means the subdir makefile won't see it.

1) What is the point of doing that?  Why not just leave them out of
   the list?

2) Why are we preventing people from overriding these at the top
   level?

zw