Simplest way to reverse the order of strings in a make variable

Let's say you have a variable in a makefile fragment like the following:

MY_LIST=a b c d

How do I then reverse the order of that list? I need:

$(warning MY_LIST=${MY_LIST})

to show

MY_LIST=d c b a

Edit: the real problem is that

ld -r some_object.o ${MY_LIST}

produces an a.out with undefined symbols because the items in MY_LIST are actually archives, but in the wrong order. If the order of MY_LIST is reversed, it will link correctly (I think). If you know a smarter way to get the link order right, clue me in.

From stackoverflow Ben Collins

• If it's GNU Makefile, you could may be run shell with $(shell echo $MY_LIST | rev).

  Your dependency issue looks weird. You could make bigger archives first, like ((c d) a b), but the compiler usually cope with that.

  Ben Collins : Heh. Nice try :-) rev reverses all the characters, too, not just the strings. echo 'lib1.a lib2.a lib3.a' | rev results in "a.3bil a.2bil a.1bil"

  elmarco : oups :) it works with your example though!

  Ben Collins : I went ahead and accepted your answer, cuz it made me think of the real answer.

  elmarco : thanks :) Awk is good at that too: echo one two three | awk '{ for (i=NF; i>0; i--) { printf "%s ", $i; } printf "\n" }'
  From elmarco

• Doh! I could have just used a shell script-let:

  (for d in ${MY_LIST}; do echo $$d; done) | tac

  elmarco : $ for d in one two three; do echo $d; done | tac three two one Superflous \n. But it's cool to learn about tac.
  From Ben Collins

• You can also define search groups with ld:

  ld -r foo.o -( a.a b.a c.a -)
  

  Will iterate through a.a, b.a, and c.a until no new unresolved symbols can be satisfied by any object in the group.

  If you're using gnu ld, you can also do:

  ld -r -o foo.o --whole-archive bar.a
  

  Which is slightly stronger, in that it will include every object from bar.a regardless of whether it satisfies an unresolved symbol from foo.o.

  From ajax

• A solution in pure GNU make:

  default: all

  foo = please reverse me

  reverse = $(if $(1),$(call reverse,$(wordlist 2,$(words $(1)),$(1)))) $(firstword $(1))

  all : @echo $(call reverse,$(foo))

  Gives:

  $ make

  me reverse please

  From $pageUsers[$post.author].name