1# $NetBSD: varname-empty.mk,v 1.5 2020/08/22 21:22:24 rillig Exp $
2#
3# Tests for the special variable with the empty name.
4#
5# The variable "" is not supposed to be assigned any value.
6# This is because it is heavily used in the .for loop expansion,
7# as well as to generate arbitrary strings, as in ${:Ufallback}.
8
9# Until 2020-08-22 it was possible to assign a value to the variable with
10# the empty name, leading to all kinds of unexpected effects.
11?=	default
12=	assigned	# undefined behavior until 2020-08-22
13+=	appended
14:=	subst
15!=	echo 'shell-output'
16
17# The .for loop expands the expression ${i} to ${:U1}, ${:U2} and so on.
18# This only works if the variable with the empty name is guaranteed to
19# be undefined.
20.for i in 1 2 3
21NUMBERS+=	${i}
22.endfor
23
24all:
25	@echo out: ${:Ufallback}
26	@echo out: ${NUMBERS}
27