$(info ...) in variable, with expansion in recipes

[Yann Droneaud]

Hi,

I'm a bit puzzled regarding the behavor of make: I don't understand why 
a make function is executed twice when stored in a variable which is 
expanded as part of a recipe.

See the following Makefile fragment, as info.mk:

  ifeq ($(V),1)
  Q :=
  else
  Q ?= @
  endif

  all:
        $(Q) : $(info 1)
        $(Q)$(RECIPE)
        $(Q) : $(info 3)

When make is invoked with

  $ $ ./make -f ./info.mk
  1
  3

Now, let's put some shell in RECIPE variable:

  $ make -f ./info.mk RECIPE='echo 2'
  1
  3
  2

Having 2 printed after 3 is OK here: $(info ...) in the recipe were 
expanded before each command were feed to the shell for execution.

Now, try to get 2 printed between 1 and 3:

  $ ./make -f ./info.mk RECIPE=': $(info 2)'
  1
  2
  3
  2

This way, 2 is printed twice. The second times seems to happen just
before passing to the shell the line where the variable is expanded.
That can be checked with

  $ ./make -f ./info.mk V=1 RECIPE=': $(info 2)'
  1
  2
  3
  : 
  2
  : 
  : 

So the second 2 (!) seems to be reported after recipe line

        $(Q) : $(info 1)

is executed by the shell, but before this recipe line

        $(Q)$(RECIPE)

is executed by the shell.

As I haven't done my homework, I don't know if it's an expected 
documented behavor. But it's a pity it behave this way.

Is there any workaround to have 2 printed only one ?

BTW, it seems to happen only with $(info ...), as it would be very bad
if other functions having side effect would be called twice. See for
example:

  $ ./make -f ./info.mk V=1 RECIPE=': $(shell mktemp info.XXXXXXXXX)'
  1
  3
  : 
  : info.vB12nZmM7
  : 

As you can see, hopefully, $(shell ...) is expanded once.

Regards.

-- 
Yann Droneaud
OPTEYA