a BSD make tool (derived from NetBSD’s make).
| cond-short.mk (bmake-20201101) | : | cond-short.mk (bmake-20201117) |
|---|
|
| # $NetBSD: cond-short.mk,v 1.11 2020/10/24 08:50:17 rillig Exp $ | | # $NetBSD: cond-short.mk,v 1.12 2020/11/15 14:58:14 rillig Exp $ |
| # | | # |
| # Demonstrates that in conditions, the right-hand side of an && or || | | # Demonstrates that in conditions, the right-hand side of an && or || |
| # is only evaluated if it can actually influence the result. | | # is only evaluated if it can actually influence the result. |
|
| | # This is called 'short-circuit evaluation' and is the usual evaluation |
| | # mode in most programming languages. A notable exception is Ada, which |
| | # distinguishes between the operators 'And', 'And Then', 'Or', 'Or Else'. |
| # | | # |
| # Between 2015-10-11 and 2020-06-28, the right-hand side of an && or || | | # Between 2015-10-11 and 2020-06-28, the right-hand side of an && or || |
| # operator was always evaluated, which was wrong. | | # operator was always evaluated, which was wrong. |
|
| # | | # TODO: Had the evaluation been correct at some time before 2015-11-12? |
| | |
| # The && operator. | | # The && operator. |
| | |
| .if 0 && ${echo "unexpected and" 1>&2 :L:sh} | | .if 0 && ${echo "unexpected and" 1>&2 :L:sh} |
| .endif | | .endif |
| | |
| .if 1 && ${echo "expected and" 1>&2 :L:sh} | | .if 1 && ${echo "expected and" 1>&2 :L:sh} |
| .endif | | .endif |
| | |
| .if 0 && exists(nonexistent${echo "unexpected and exists" 1>&2 :L:sh}) | | .if 0 && exists(nonexistent${echo "unexpected and exists" 1>&2 :L:sh}) |
| | |
| skipping to change at line 116 | | skipping to change at line 119 |
|---|
| . endif | | . endif |
| .endif | | .endif |
| | |
| .if 1 | | .if 1 |
| .elif ${echo "unexpected nested or" 1>&2 :L:sh} | | .elif ${echo "unexpected nested or" 1>&2 :L:sh} |
| .endif | | .endif |
| | |
| # make sure these do not cause complaint | | # make sure these do not cause complaint |
| #.MAKEFLAGS: -dc | | #.MAKEFLAGS: -dc |
| | |
|
| | # TODO: Rewrite this whole section and check all the conditions and variables. |
| | # Several of the assumptions are probably wrong here. |
| | # TODO: replace 'x=' with '.info' or '.error'. |
| V42= 42 | | V42= 42 |
| iV1= ${V42} | | iV1= ${V42} |
| iV2= ${V66} | | iV2= ${V66} |
| | |
| .if defined(V42) && ${V42} > 0 | | .if defined(V42) && ${V42} > 0 |
| x= Ok | | x= Ok |
| .else | | .else |
| x= Fail | | x= Fail |
| .endif | | .endif |
| x!= echo 'defined(V42) && ${V42} > 0: $x' >&2; echo | | x!= echo 'defined(V42) && ${V42} > 0: $x' >&2; echo |
| | |
| skipping to change at line 170 | | skipping to change at line 176 |
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| x!= echo '0 || ${iV1} <= ${V42}: $x' >&2; echo | | x!= echo '0 || ${iV1} <= ${V42}: $x' >&2; echo |
| | |
| # ${iV2:U2} expands to 2 | | # ${iV2:U2} expands to 2 |
| .if 0 || ${iV2:U2} < ${V42} | | .if 0 || ${iV2:U2} < ${V42} |
| x= Ok | | x= Ok |
| .else | | .else |
| x= Fail | | x= Fail |
| .endif | | .endif |
| x!= echo '0 || ${iV2:U2} < ${V42}: $x' >&2; echo | | x!= echo '0 || ${iV2:U2} < ${V42}: $x' >&2; echo |
| | |
|
| | # TODO: Has this always worked? There may have been a time, maybe around |
| | # 2000, when make would complain about the "Malformed conditional" because |
| | # UNDEF is not defined. |
| | .if defined(UNDEF) && ${UNDEF} != "undefined" |
| | . error |
| | .endif |
| | |
| | # TODO: Test each modifier to make sure it is skipped when it is irrelevant |
| | # for the result. Since this test is already quite long, do that in another |
| | # test. |
| | |
| all: | | all: |
| @:;: | | @:;: |
| | | |
| End of changes. 5 change blocks. |
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| 2 lines changed or deleted | | 19 lines changed or added |
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