Re: make-4.0 allows empty ARFLAGS to be passed to ar

[Paul Smith]

On Mon, 2013-10-21 at 18:03 +0100, Ken Moffat wrote:
> 2. Unfortunately, rules.mak *is* adding -rR to the MAKEFLAGS -
> 
> # Don't use implicit rules or variables
> # we have explicit rules for everything
> MAKEFLAGS += -rR

>  I'll attach rules.mak.  Is this a qemu bug which just happened to
> work in make-3.82, or a make problem ?

It's a qemu bug, that just happened to work with make-3.82.  By adding
the -R flag they are stating they don't want to use ANY default variable
values.  However they are relying on the default variable value for
ARFLAGS to be set.  If they want to use -R they should set ARFLAGS to an
acceptable value in their makefile.

In previous versions of GNU make adding those flags wouldn't take effect
in the current instance of make; it would only be in effect in a
sub-make; that bug/mis-feature was fixed in GNU make 4.0.  Now adding
those flags in a makefile takes effect immediately, within that same
instance of make.  From the NEWS for GNU make 4.0:

* Setting the -r and -R options in MAKEFLAGS inside a makefile now works as
  expected, removing all built-in rules and variables, respectively.