RFA/RFC: Pass --cache-file=/dev/null on to subconfigures

[Nick Clifton <nickc at redhat dot com>]

Hi Guys,

  I am regularly encountering problems rebuilding my toolchains
  because the config.cache file in one or more of the sub-directories
  is inconsistent:

configure: error: run `make distclean' and/or `rm ./config.cache' and start over
  
  This is annoying because it stops the automated build process and I
  have to manually remove the cache file before I can resume it.
  Since I am not worried about the time it takes to rerun the
  configure script in these sub-directories I would like to be able to
  build the entire toolchain without using any caches.

  In theory I can specify "--cache-file=/dev/null" when configuring
  the toolchain.  Unfortunately the top level configure file strips
  out all --cache-file arguments before invoking configure in any of
  the sub-directories.  Although this might be reasonable for a
  configure cache that is specified via an absolute path, it is
  unreasonable when the user is trying to disable caches altogether.

  So I have created the patch below.  It simply allows
  --cache-file=/dev/null to be passed on to the configure scripts in
  the sub-directories.  I have run a gcc bootstrap without problems
  and so I would like to apply the patch.

  Any comments or reasons why the patch should not be applied ?

Cheers
  Nick

./ChangeLog
2009-09-25  Nick Clifton  <nickc@redhat.com>

	* configure.ac: Pass any --cache-file=/dev/null option on to
	subconfigures.
	* configure: Regenerate.

Index: configure.ac
===================================================================
--- configure.ac	(revision 152111)
+++ configure.ac	(working copy)
@@ -2632,9 +2632,11 @@
 
 # Base args.  Strip norecursion, cache-file, srcdir, host, build,
 # target, nonopt, and variable assignments.  These are the ones we
-# might not want to pass down to subconfigures.  Also strip
-# program-prefix, program-suffix, and program-transform-name, so that
-# we can pass down a consistent program-transform-name.
+# might not want to pass down to subconfigures.  The exception being
+# --cache-file=/dev/null, which is used to turn off the use of cache
+# files altogether, and which should be passed on to subconfigures.
+# Also strip program-prefix, program-suffix, and program-transform-name,
+# so that we can pass down a consistent program-transform-name.
 baseargs=
 keep_next=no
 skip_next=no
@@ -2673,6 +2675,13 @@
   esac
 
   case "$ac_arg" in
+    --cache-file=/dev/null | \
+    -cache-file=/dev/null )
+      # Handled here to avoid the test to skip args below.
+      baseargs="$baseargs '$ac_arg'"
+      # Assert: $separate_arg should always be no.
+      keep_next=$separate_arg
+      ;;
     --no*)
       continue
       ;;