1# $NetBSD: varmod-ifelse.mk,v 1.5 2020/10/23 14:24:51 rillig Exp $ 2# 3# Tests for the ${cond:?then:else} variable modifier, which evaluates either 4# the then-expression or the else-expression, depending on the condition. 5# 6# The modifier was added on 1998-04-01. 7# 8# Until 2015-10-11, the modifier always evaluated both the "then" and the 9# "else" expressions. 10 11# TODO: Implementation 12 13# The variable name of the expression is expanded and then taken as the 14# condition. In this case it becomes: 15# 16# variable expression == "variable expression" 17# 18# This confuses the parser, which expects an operator instead of the bare 19# word "expression". If the name were expanded lazily, everything would be 20# fine since the condition would be: 21# 22# ${:Uvariable expression} == "literal" 23# 24# Evaluating the variable name lazily would require additional code in 25# Var_Parse and ParseVarname, it would be more useful and predictable 26# though. 27.if ${${:Uvariable expression} == "literal":?bad:bad} 28. error 29.else 30. error 31.endif 32 33# In a variable assignment, undefined variables are not an error. 34# Because of the early expansion, the whole condition evaluates to 35# ' == ""' though, which cannot be parsed because the left-hand side looks 36# empty. 37COND:= ${${UNDEF} == "":?bad-assign:bad-assign} 38 39# In a condition, undefined variables generate a "Malformed conditional" 40# error. That error message is wrong though. In lint mode, the correct 41# "Undefined variable" error message is generated. 42# The difference to the ':=' variable assignment is the additional 43# "Malformed conditional" error message. 44.if ${${UNDEF} == "":?bad-cond:bad-cond} 45. error 46.else 47. error 48.endif 49 50# When the :? is parsed, it is greedy. The else branch spans all the 51# text, up until the closing character '}', even if the text looks like 52# another modifier. 53.if ${1:?then:else:Q} != "then" 54. error 55.endif 56.if ${0:?then:else:Q} != "else:Q" 57. error 58.endif 59 60all: 61 @:; 62