1 # $NetBSD: varname-empty.mk,v 1.5 2020/08/22 21:22:24 rillig Exp $
3 # Tests for the special variable with the empty name.
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}.
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.
12 = assigned # undefined behavior until 2020-08-22
15 != echo 'shell-output'
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
25 @echo out: ${:Ufallback}