Re: recursive make variables coming to POSIX

[Ralf Wildenhues]

Hi Eric,

* Eric Blake wrote on Thu, Dec 02, 2010 at 08:21:13PM CET:
> On 12/02/2010 12:10 PM, Ralf Wildenhues wrote:
> > I'm not sure if it was mentioned before in the discussion, but
> > portability-wise, there is a difference between one level of recursion
> > and arbitrary many.  IIRC then IRIX make only supported one level, i.e.,
> >   $(var1$(var2$(var3)))
> > 
> > was erroneous, but
> >   $(var1$(var2))
> > 
> > was not.  Also, with a one-character variable X
> >   $(var$X)
> > 
> > was erroneous with at least one legacy make implementation (but I think
> > it was more than one); but
> >   $(var$(X))
> > 
> > worked.
> > 
> > If you like, I can go back and verify the details.
> 
> Yes please, and I will feed that information back to the Austin Group.

Thank you.  Here we go.  With the following Makefile,

V = v
V1 = v1
V11 = v11
O = 1
ONE = 1
O1 = 11
Vr1 = $(V$(O))
Vr2 = $(V$(ONE))
Vr3 = $(V$(Z))
Vr4 = $(V$O)
Vr5 = $(V$Z)
Vrr1 = $(V$(O$(Z)))
Vrr2 = $(V$(O$(O)))
Vrr3 = $(V$(Z$(Z)))
Vrr4 = $(V$(O$Z))
Vrr5 = $(V$(Z$Z))
R = R
Vrrr = $($($($($($($($($($($($($($(R))))))))))))))
all_FLAGS = bar

all:
        @echo $(Vr1), $(Vr2), $(Vr3)
        @echo $(Vrr1), $(Vrr2), $(Vrr3)
        @echo $(Vrrr)
        @echo $(Vr4), $(Vr5)
        @echo $(Vrr4), $(Vrr5)
        @echo $(address@hidden)
        @echo $($(@)_FLAGS)

the make implementations from
  AIX 5.2, 5.3, 6.1, 7.1
  Darwin 10.4.0 (GNU make 3.81)
  FreeBSD 6.4, 7.1
  GNU
  HP-UX 10.20, 11.00, 11.11, 11.23, 11.31
  NetBSD 5.99.39
  OpenBSD 4.4
  Solaris 2.6, 7, 8, 9, 10
  Tru64 OSF 5.1D

all print:

v1, v1, v
v1, v11, v
R
v1, v
v1, v
bar
bar

IRIX 6.5 make fails over each expansion in output lines 5, 6, and 7,
e.g.:

v1, v1, v
v1, v11, v
R
UX:make: ERROR: Unmatched closing curly braces or parenthesis in line 
containing:
        $(V$O).


The last line containing $($(@)_FLAGS) is wrongly expanded to empty by
this make.


So, in summary, the parenthesization is an issue, and expanding of the
automatic $@ variable recursively.  I haven't tried to determine whether
there is an upper limit to recursive expansion (should I?).

See also this old thread:
<http://thread.gmane.org/gmane.comp.sysutils.automake.general/9943/focus=9945>

Cheers,
Ralf