cond-short.mk revision 1.12
1 # $NetBSD: cond-short.mk,v 1.12 2020/11/15 14:58:14 rillig Exp $ 2 # 3 # Demonstrates that in conditions, the right-hand side of an && or || 4 # is only evaluated if it can actually influence the result. 5 # This is called 'short-circuit evaluation' and is the usual evaluation 6 # mode in most programming languages. A notable exception is Ada, which 7 # distinguishes between the operators 'And', 'And Then', 'Or', 'Or Else'. 8 # 9 # Between 2015-10-11 and 2020-06-28, the right-hand side of an && or || 10 # operator was always evaluated, which was wrong. 11 # TODO: Had the evaluation been correct at some time before 2015-11-12? 12 13 # The && operator. 14 15 .if 0 && ${echo "unexpected and" 1>&2 :L:sh} 16 .endif 17 18 .if 1 && ${echo "expected and" 1>&2 :L:sh} 19 .endif 20 21 .if 0 && exists(nonexistent${echo "unexpected and exists" 1>&2 :L:sh}) 22 .endif 23 24 .if 1 && exists(nonexistent${echo "expected and exists" 1>&2 :L:sh}) 25 .endif 26 27 .if 0 && empty(${echo "unexpected and empty" 1>&2 :L:sh}) 28 .endif 29 30 .if 1 && empty(${echo "expected and empty" 1>&2 :L:sh}) 31 .endif 32 33 # "VAR U11" is not evaluated; it was evaluated before 2020-07-02. 34 # The whole !empty condition is only parsed and then discarded. 35 VAR= ${VAR${:U11${echo "unexpected VAR U11" 1>&2 :L:sh}}} 36 VAR13= ${VAR${:U12${echo "unexpected VAR13" 1>&2 :L:sh}}} 37 .if 0 && !empty(VAR${:U13${echo "unexpected U13 condition" 1>&2 :L:sh}}) 38 .endif 39 40 VAR= ${VAR${:U21${echo "unexpected VAR U21" 1>&2 :L:sh}}} 41 VAR23= ${VAR${:U22${echo "expected VAR23" 1>&2 :L:sh}}} 42 .if 1 && !empty(VAR${:U23${echo "expected U23 condition" 1>&2 :L:sh}}) 43 .endif 44 VAR= # empty again, for the following tests 45 46 # The :M modifier is only parsed, not evaluated. 47 # Before 2020-07-02, it was wrongly evaluated. 48 .if 0 && !empty(VAR:M${:U${echo "unexpected M pattern" 1>&2 :L:sh}}) 49 .endif 50 51 .if 1 && !empty(VAR:M${:U${echo "expected M pattern" 1>&2 :L:sh}}) 52 .endif 53 54 .if 0 && !empty(VAR:S,from,${:U${echo "unexpected S modifier" 1>&2 :L:sh}},) 55 .endif 56 57 .if 0 && !empty(VAR:C,from,${:U${echo "unexpected C modifier" 1>&2 :L:sh}},) 58 .endif 59 60 .if 0 && !empty("" == "" :? ${:U${echo "unexpected ? modifier" 1>&2 :L:sh}} :) 61 .endif 62 63 .if 0 && !empty(VAR:old=${:U${echo "unexpected = modifier" 1>&2 :L:sh}}) 64 .endif 65 66 .if 0 && !empty(1 2 3:L:@var@${:U${echo "unexpected @ modifier" 1>&2 :L:sh}}@) 67 .endif 68 69 .if 0 && !empty(:U${:!echo "unexpected exclam modifier" 1>&2 !}) 70 .endif 71 72 # Irrelevant assignment modifiers are skipped as well. 73 .if 0 && ${1 2 3:L:@i@${FIRST::?=$i}@} 74 .endif 75 .if 0 && ${1 2 3:L:@i@${LAST::=$i}@} 76 .endif 77 .if 0 && ${1 2 3:L:@i@${APPENDED::+=$i}@} 78 .endif 79 .if 0 && ${echo.1 echo.2 echo.3:L:@i@${RAN::!=${i:C,.*,&; & 1>\&2,:S,., ,g}}@} 80 .endif 81 .if defined(FIRST) || defined(LAST) || defined(APPENDED) || defined(RAN) 82 . warning first=${FIRST} last=${LAST} appended=${APPENDED} ran=${RAN} 83 .endif 84 85 # The || operator. 86 87 .if 1 || ${echo "unexpected or" 1>&2 :L:sh} 88 .endif 89 90 .if 0 || ${echo "expected or" 1>&2 :L:sh} 91 .endif 92 93 .if 1 || exists(nonexistent${echo "unexpected or exists" 1>&2 :L:sh}) 94 .endif 95 96 .if 0 || exists(nonexistent${echo "expected or exists" 1>&2 :L:sh}) 97 .endif 98 99 .if 1 || empty(${echo "unexpected or empty" 1>&2 :L:sh}) 100 .endif 101 102 .if 0 || empty(${echo "expected or empty" 1>&2 :L:sh}) 103 .endif 104 105 # Unreachable nested conditions are skipped completely as well. 106 107 .if 0 108 . if ${echo "unexpected nested and" 1>&2 :L:sh} 109 . endif 110 .endif 111 112 .if 1 113 .elif ${echo "unexpected nested or" 1>&2 :L:sh} 114 .endif 115 116 # make sure these do not cause complaint 117 #.MAKEFLAGS: -dc 118 119 # TODO: Rewrite this whole section and check all the conditions and variables. 120 # Several of the assumptions are probably wrong here. 121 # TODO: replace 'x=' with '.info' or '.error'. 122 V42= 42 123 iV1= ${V42} 124 iV2= ${V66} 125 126 .if defined(V42) && ${V42} > 0 127 x= Ok 128 .else 129 x= Fail 130 .endif 131 x!= echo 'defined(V42) && ${V42} > 0: $x' >&2; echo 132 133 # this one throws both String comparison operator and 134 # Malformed conditional with cond.c 1.78 135 # indirect iV2 would expand to "" and treated as 0 136 .if defined(V66) && ( ${iV2} < ${V42} ) 137 x= Fail 138 .else 139 x= Ok 140 .endif 141 x!= echo 'defined(V66) && ( "${iV2}" < ${V42} ): $x' >&2; echo 142 143 # next two thow String comparison operator with cond.c 1.78 144 # indirect iV1 would expand to 42 145 .if 1 || ${iV1} < ${V42} 146 x= Ok 147 .else 148 x= Fail 149 .endif 150 x!= echo '1 || ${iV1} < ${V42}: $x' >&2; echo 151 152 .if 1 || ${iV2:U2} < ${V42} 153 x= Ok 154 .else 155 x= Fail 156 .endif 157 x!= echo '1 || ${iV2:U2} < ${V42}: $x' >&2; echo 158 159 # the same expressions are fine when the lhs is expanded 160 # ${iV1} expands to 42 161 .if 0 || ${iV1} <= ${V42} 162 x= Ok 163 .else 164 x= Fail 165 .endif 166 x!= echo '0 || ${iV1} <= ${V42}: $x' >&2; echo 167 168 # ${iV2:U2} expands to 2 169 .if 0 || ${iV2:U2} < ${V42} 170 x= Ok 171 .else 172 x= Fail 173 .endif 174 x!= echo '0 || ${iV2:U2} < ${V42}: $x' >&2; echo 175 176 # TODO: Has this always worked? There may have been a time, maybe around 177 # 2000, when make would complain about the "Malformed conditional" because 178 # UNDEF is not defined. 179 .if defined(UNDEF) && ${UNDEF} != "undefined" 180 . error 181 .endif 182 183 # TODO: Test each modifier to make sure it is skipped when it is irrelevant 184 # for the result. Since this test is already quite long, do that in another 185 # test. 186 187 all: 188 @:;: 189
Indexes created Sun Oct 19 02:09:48 GMT 2025