37 lines
1.2 KiB
Makefile
37 lines
1.2 KiB
Makefile
# $NetBSD: cond-late.mk,v 1.6 2023/12/10 20:12:28 rillig Exp $
|
|
#
|
|
# Using the :? modifier, expressions can contain conditional
|
|
# expressions that are evaluated late, at expansion time.
|
|
#
|
|
# Any expressions appearing in these conditions are expanded before parsing
|
|
# the condition. This is different from conditions in .if directives, where
|
|
# expressions are evaluated individually and only as far as necessary, see
|
|
# cond-short.mk.
|
|
#
|
|
# Because of this, variables that are used in these lazy conditions
|
|
# should not contain double-quotes, or the parser will probably fail.
|
|
#
|
|
# They should also not contain operators like == or <, since these are
|
|
# actually interpreted as these operators. This is demonstrated below.
|
|
#
|
|
|
|
all: cond-literal
|
|
|
|
COND.true= "yes" == "yes"
|
|
COND.false= "yes" != "yes"
|
|
|
|
# If the order of evaluation were to change to first parse the condition
|
|
# and then expand the variables, the output would change from the
|
|
# current "yes no" to "yes yes", since both variables are non-empty.
|
|
# expect: yes
|
|
# expect: no
|
|
cond-literal:
|
|
@echo ${ ${COND.true} :?yes:no}
|
|
@echo ${ ${COND.false} :?yes:no}
|
|
|
|
VAR= ${${UNDEF} != "no":?:}
|
|
# expect-reset
|
|
# expect: make: Bad conditional expression ' != "no"' before '?:'
|
|
.if empty(VAR:Mpattern)
|
|
.endif
|