user hostile gobbledygook in top level Makefile

[Alexandre Oliva]

On Nov 19, 2000, "Zack Weinberg" <zackw@stanford.edu> wrote:

> So I'm trying to figure out why I can't override BOOT_CFLAGS on the
> command line from the top level

You can.  Or, at least, you're supposed to be able to do it.

> I see this in the top Makefile.in:

> 	"`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.

You're sorely confused :-)

Note the `$$'.  The purpose seems to be to replace `BOOT_CFLAGS=' with
`XFOO=', as long as $(BOOT_CFLAGS) is empty.  I.e., if you set
BOOT_CFLAGS to non-empty, it will be passed down, but if you don't
override it (note that it's not set in the top-level Makefile), you
don't get the definition in the sub-directory overridden by the
non-definition in the top level.

-- 
Alexandre Oliva   Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
Red Hat GCC Developer                  aoliva@{cygnus.com, redhat.com}
CS PhD student at IC-Unicamp        oliva@{lsd.ic.unicamp.br, gnu.org}
Free Software Evangelist    *Please* write to mailing lists, not to me