7d6be9ffc4
Before 2020-08-22, the command line argument '=cmline-plain' triggered undefined behavior, just like the assignment '=assigned' in the Makefile.
27 lines
811 B
Makefile
27 lines
811 B
Makefile
# $NetBSD: varname-empty.mk,v 1.5 2020/08/22 21:22:24 rillig Exp $
|
|
#
|
|
# Tests for the special variable with the empty name.
|
|
#
|
|
# The variable "" is not supposed to be assigned any value.
|
|
# This is because it is heavily used in the .for loop expansion,
|
|
# as well as to generate arbitrary strings, as in ${:Ufallback}.
|
|
|
|
# Until 2020-08-22 it was possible to assign a value to the variable with
|
|
# the empty name, leading to all kinds of unexpected effects.
|
|
?= default
|
|
= assigned # undefined behavior until 2020-08-22
|
|
+= appended
|
|
:= subst
|
|
!= echo 'shell-output'
|
|
|
|
# The .for loop expands the expression ${i} to ${:U1}, ${:U2} and so on.
|
|
# This only works if the variable with the empty name is guaranteed to
|
|
# be undefined.
|
|
.for i in 1 2 3
|
|
NUMBERS+= ${i}
|
|
.endfor
|
|
|
|
all:
|
|
@echo out: ${:Ufallback}
|
|
@echo out: ${NUMBERS}
|