1# $NetBSD: cond-short.mk,v 1.15 2020/12/01 19:37:23 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# Before 2020-06-28, the right-hand side of an && or || operator was always 10# evaluated, which was wrong. In cond.c 1.69 and var.c 1.197 on 2015-10-11, 11# Var_Parse got a new parameter named 'wantit'. Since then it would have been 12# possible to skip evaluation of irrelevant variable expressions and only 13# parse them. They were still evaluated though, the only difference to 14# relevant variable expressions was that in the irrelevant variable 15# expressions, undefined variables were allowed. 16 17# The && operator. 18 19.if 0 && ${echo "unexpected and" 1>&2 :L:sh} 20.endif 21 22.if 1 && ${echo "expected and" 1>&2 :L:sh} 23.endif 24 25.if 0 && exists(nonexistent${echo "unexpected and exists" 1>&2 :L:sh}) 26.endif 27 28.if 1 && exists(nonexistent${echo "expected and exists" 1>&2 :L:sh}) 29.endif 30 31.if 0 && empty(${echo "unexpected and empty" 1>&2 :L:sh}) 32.endif 33 34.if 1 && empty(${echo "expected and empty" 1>&2 :L:sh}) 35.endif 36 37# "VAR U11" is not evaluated; it was evaluated before 2020-07-02. 38# The whole !empty condition is only parsed and then discarded. 39VAR= ${VAR${:U11${echo "unexpected VAR U11" 1>&2 :L:sh}}} 40VAR13= ${VAR${:U12${echo "unexpected VAR13" 1>&2 :L:sh}}} 41.if 0 && !empty(VAR${:U13${echo "unexpected U13 condition" 1>&2 :L:sh}}) 42.endif 43 44VAR= ${VAR${:U21${echo "unexpected VAR U21" 1>&2 :L:sh}}} 45VAR23= ${VAR${:U22${echo "expected VAR23" 1>&2 :L:sh}}} 46.if 1 && !empty(VAR${:U23${echo "expected U23 condition" 1>&2 :L:sh}}) 47.endif 48VAR= # empty again, for the following tests 49 50# The :M modifier is only parsed, not evaluated. 51# Before 2020-07-02, it was wrongly evaluated. 52.if 0 && !empty(VAR:M${:U${echo "unexpected M pattern" 1>&2 :L:sh}}) 53.endif 54 55.if 1 && !empty(VAR:M${:U${echo "expected M pattern" 1>&2 :L:sh}}) 56.endif 57 58.if 0 && !empty(VAR:S,from,${:U${echo "unexpected S modifier" 1>&2 :L:sh}},) 59.endif 60 61.if 0 && !empty(VAR:C,from,${:U${echo "unexpected C modifier" 1>&2 :L:sh}},) 62.endif 63 64.if 0 && !empty("" == "" :? ${:U${echo "unexpected ? modifier" 1>&2 :L:sh}} :) 65.endif 66 67.if 0 && !empty(VAR:old=${:U${echo "unexpected = modifier" 1>&2 :L:sh}}) 68.endif 69 70.if 0 && !empty(1 2 3:L:@var@${:U${echo "unexpected @ modifier" 1>&2 :L:sh}}@) 71.endif 72 73.if 0 && !empty(:U${:!echo "unexpected exclam modifier" 1>&2 !}) 74.endif 75 76# Irrelevant assignment modifiers are skipped as well. 77.if 0 && ${1 2 3:L:@i@${FIRST::?=$i}@} 78.endif 79.if 0 && ${1 2 3:L:@i@${LAST::=$i}@} 80.endif 81.if 0 && ${1 2 3:L:@i@${APPENDED::+=$i}@} 82.endif 83.if 0 && ${echo.1 echo.2 echo.3:L:@i@${RAN::!=${i:C,.*,&; & 1>\&2,:S,., ,g}}@} 84.endif 85.if defined(FIRST) || defined(LAST) || defined(APPENDED) || defined(RAN) 86. warning first=${FIRST} last=${LAST} appended=${APPENDED} ran=${RAN} 87.endif 88 89# The || operator. 90 91.if 1 || ${echo "unexpected or" 1>&2 :L:sh} 92.endif 93 94.if 0 || ${echo "expected or" 1>&2 :L:sh} 95.endif 96 97.if 1 || exists(nonexistent${echo "unexpected or exists" 1>&2 :L:sh}) 98.endif 99 100.if 0 || exists(nonexistent${echo "expected or exists" 1>&2 :L:sh}) 101.endif 102 103.if 1 || empty(${echo "unexpected or empty" 1>&2 :L:sh}) 104.endif 105 106.if 0 || empty(${echo "expected or empty" 1>&2 :L:sh}) 107.endif 108 109# Unreachable nested conditions are skipped completely as well. 110 111.if 0 112. if ${echo "unexpected nested and" 1>&2 :L:sh} 113. endif 114.endif 115 116.if 1 117.elif ${echo "unexpected nested or" 1>&2 :L:sh} 118.endif 119 120# make sure these do not cause complaint 121#.MAKEFLAGS: -dc 122 123# TODO: Rewrite this whole section and check all the conditions and variables. 124# Several of the assumptions are probably wrong here. 125# TODO: replace 'x=' with '.info' or '.error'. 126V42= 42 127iV1= ${V42} 128iV2= ${V66} 129 130.if defined(V42) && ${V42} > 0 131x= Ok 132.else 133x= Fail 134.endif 135x!= echo 'defined(V42) && $${V42} > 0: $x' >&2; echo 136 137# With cond.c 1.76 from 2020-07-03, the following condition triggered a 138# warning: "String comparison operator should be either == or !=". 139# This was because the variable expression ${iV2} was defined, but the 140# contained variable V66 was undefined. The left-hand side of the comparison 141# therefore evaluated to the string "${V66}", which is obviously not a number. 142# 143# This was fixed in cond.c 1.79 from 2020-07-09 by not evaluating irrelevant 144# comparisons. Instead, they are only parsed and then discarded. 145# 146# At that time, there was not enough debug logging to see the details in the 147# -dA log. To actually see it, add debug logging at the beginning and end of 148# Var_Parse. 149.if defined(V66) && ( ${iV2} < ${V42} ) 150x= Fail 151.else 152x= Ok 153.endif 154# XXX: This condition doesn't match the one above. The quotes are missing 155# above. This is a crucial detail since without quotes, the variable 156# expression ${iV2} evaluates to "${V66}", and with quotes, it evaluates to "" 157# since undefined variables are allowed and expand to an empty string. 158x!= echo 'defined(V66) && ( "$${iV2}" < $${V42} ): $x' >&2; echo 159 160.if 1 || ${iV1} < ${V42} 161x= Ok 162.else 163x= Fail 164.endif 165x!= echo '1 || $${iV1} < $${V42}: $x' >&2; echo 166 167# With cond.c 1.76 from 2020-07-03, the following condition triggered a 168# warning: "String comparison operator should be either == or !=". 169# This was because the variable expression ${iV2} was defined, but the 170# contained variable V66 was undefined. The left-hand side of the comparison 171# therefore evaluated to the string "${V66}", which is obviously not a number. 172# 173# This was fixed in cond.c 1.79 from 2020-07-09 by not evaluating irrelevant 174# comparisons. Instead, they are only parsed and then discarded. 175# 176# At that time, there was not enough debug logging to see the details in the 177# -dA log. To actually see it, add debug logging at the beginning and end of 178# Var_Parse. 179.if 1 || ${iV2:U2} < ${V42} 180x= Ok 181.else 182x= Fail 183.endif 184x!= echo '1 || $${iV2:U2} < $${V42}: $x' >&2; echo 185 186# the same expressions are fine when the lhs is expanded 187# ${iV1} expands to 42 188.if 0 || ${iV1} <= ${V42} 189x= Ok 190.else 191x= Fail 192.endif 193x!= echo '0 || $${iV1} <= $${V42}: $x' >&2; echo 194 195# ${iV2:U2} expands to 2 196.if 0 || ${iV2:U2} < ${V42} 197x= Ok 198.else 199x= Fail 200.endif 201x!= echo '0 || $${iV2:U2} < $${V42}: $x' >&2; echo 202 203# The right-hand side of the '&&' is irrelevant since the left-hand side 204# already evaluates to false. Before cond.c 1.79 from 2020-07-09, it was 205# expanded nevertheless, although with a small modification: undefined 206# variables may be used in these expressions without generating an error. 207.if defined(UNDEF) && ${UNDEF} != "undefined" 208. error 209.endif 210 211# TODO: Test each modifier to make sure it is skipped when it is irrelevant 212# for the result. Since this test is already quite long, do that in another 213# test. 214 215all: 216 @:;: 217