1 # $NetBSD: cond-short.mk,v 1.15 2020/12/01 19:37:23 rillig Exp $
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'.
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.
19 .if 0 && ${echo "unexpected and" 1>&2 :L:sh}
22 .if 1 && ${echo "expected and" 1>&2 :L:sh}
25 .if 0 && exists(nonexistent${echo "unexpected and exists" 1>&2 :L:sh})
28 .if 1 && exists(nonexistent${echo "expected and exists" 1>&2 :L:sh})
31 .if 0 && empty(${echo "unexpected and empty" 1>&2 :L:sh})
34 .if 1 && empty(${echo "expected and empty" 1>&2 :L:sh})
37 # "VAR U11" is not evaluated; it was evaluated before 2020-07-02.
38 # The whole !empty condition is only parsed and then discarded.
39 VAR= ${VAR${:U11${echo "unexpected VAR U11" 1>&2 :L:sh}}}
40 VAR13= ${VAR${:U12${echo "unexpected VAR13" 1>&2 :L:sh}}}
41 .if 0 && !empty(VAR${:U13${echo "unexpected U13 condition" 1>&2 :L:sh}})
44 VAR= ${VAR${:U21${echo "unexpected VAR U21" 1>&2 :L:sh}}}
45 VAR23= ${VAR${:U22${echo "expected VAR23" 1>&2 :L:sh}}}
46 .if 1 && !empty(VAR${:U23${echo "expected U23 condition" 1>&2 :L:sh}})
48 VAR= # empty again, for the following tests
50 # The :M modifier is only parsed, not evaluated.
51 # Before 2020-07-02, it was wrongly evaluated.
52 .if 0 && !empty(VAR:M${:U${echo "unexpected M pattern" 1>&2 :L:sh}})
55 .if 1 && !empty(VAR:M${:U${echo "expected M pattern" 1>&2 :L:sh}})
58 .if 0 && !empty(VAR:S,from,${:U${echo "unexpected S modifier" 1>&2 :L:sh}},)
61 .if 0 && !empty(VAR:C,from,${:U${echo "unexpected C modifier" 1>&2 :L:sh}},)
64 .if 0 && !empty("" == "" :? ${:U${echo "unexpected ? modifier" 1>&2 :L:sh}} :)
67 .if 0 && !empty(VAR:old=${:U${echo "unexpected = modifier" 1>&2 :L:sh}})
70 .if 0 && !empty(1 2 3:L:@var@${:U${echo "unexpected @ modifier" 1>&2 :L:sh}}@)
73 .if 0 && !empty(:U${:!echo "unexpected exclam modifier" 1>&2 !})
76 # Irrelevant assignment modifiers are skipped as well.
77 .if 0 && ${1 2 3:L:@i@${FIRST::?=$i}@}
79 .if 0 && ${1 2 3:L:@i@${LAST::=$i}@}
81 .if 0 && ${1 2 3:L:@i@${APPENDED::+=$i}@}
83 .if 0 && ${echo.1 echo.2 echo.3:L:@i@${RAN::!=${i:C,.*,&; & 1>\&2,:S,., ,g}}@}
85 .if defined(FIRST) || defined(LAST) || defined(APPENDED) || defined(RAN)
86 . warning first=${FIRST} last=${LAST} appended=${APPENDED} ran=${RAN}
91 .if 1 || ${echo "unexpected or" 1>&2 :L:sh}
94 .if 0 || ${echo "expected or" 1>&2 :L:sh}
97 .if 1 || exists(nonexistent${echo "unexpected or exists" 1>&2 :L:sh})
100 .if 0 || exists(nonexistent${echo "expected or exists" 1>&2 :L:sh})
103 .if 1 || empty(${echo "unexpected or empty" 1>&2 :L:sh})
106 .if 0 || empty(${echo "expected or empty" 1>&2 :L:sh})
109 # Unreachable nested conditions are skipped completely as well.
112 . if ${echo "unexpected nested and" 1>&2 :L:sh}
117 .elif ${echo "unexpected nested or" 1>&2 :L:sh}
120 # make sure these do not cause complaint
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'.
130 .if defined(V42) && ${V42} > 0
135 x!= echo 'defined(V42) && $${V42} > 0: $x' >&2; echo
137 # With cond.c 1.76 from 2020-07-03, the following condition triggered a
138 # warning: "String comparison operator should be either == or !=".
139 # This was because the variable expression ${iV2} was defined, but the
140 # contained variable V66 was undefined. The left-hand side of the comparison
141 # therefore evaluated to the string "${V66}", which is obviously not a number.
143 # This was fixed in cond.c 1.79 from 2020-07-09 by not evaluating irrelevant
144 # comparisons. Instead, they are only parsed and then discarded.
146 # At that time, there was not enough debug logging to see the details in the
147 # -dA log. To actually see it, add debug logging at the beginning and end of
149 .if defined(V66) && ( ${iV2} < ${V42} )
154 # XXX: This condition doesn't match the one above. The quotes are missing
155 # above. This is a crucial detail since without quotes, the variable
156 # expression ${iV2} evaluates to "${V66}", and with quotes, it evaluates to ""
157 # since undefined variables are allowed and expand to an empty string.
158 x!= echo 'defined(V66) && ( "$${iV2}" < $${V42} ): $x' >&2; echo
160 .if 1 || ${iV1} < ${V42}
165 x!= echo '1 || $${iV1} < $${V42}: $x' >&2; echo
167 # With cond.c 1.76 from 2020-07-03, the following condition triggered a
168 # warning: "String comparison operator should be either == or !=".
169 # This was because the variable expression ${iV2} was defined, but the
170 # contained variable V66 was undefined. The left-hand side of the comparison
171 # therefore evaluated to the string "${V66}", which is obviously not a number.
173 # This was fixed in cond.c 1.79 from 2020-07-09 by not evaluating irrelevant
174 # comparisons. Instead, they are only parsed and then discarded.
176 # At that time, there was not enough debug logging to see the details in the
177 # -dA log. To actually see it, add debug logging at the beginning and end of
179 .if 1 || ${iV2:U2} < ${V42}
184 x!= echo '1 || $${iV2:U2} < $${V42}: $x' >&2; echo
186 # the same expressions are fine when the lhs is expanded
187 # ${iV1} expands to 42
188 .if 0 || ${iV1} <= ${V42}
193 x!= echo '0 || $${iV1} <= $${V42}: $x' >&2; echo
195 # ${iV2:U2} expands to 2
196 .if 0 || ${iV2:U2} < ${V42}
201 x!= echo '0 || $${iV2:U2} < $${V42}: $x' >&2; echo
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"
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