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varmod-remember.mk revision 1.9 
      1 # $NetBSD: varmod-remember.mk,v 1.9 2023/02/09 22:21:57 rillig Exp $
      2 #
      3 # Tests for the :_ modifier, which saves the current expression value
      4 # in the _ variable or another, to be used later again.
      5 
      6 
      7 # The ':_' modifier is typically used in situations where the value of an
      8 # expression is needed at the same time as a sequence of numbers.  In these
      9 # cases, the value of the expression is saved in the temporary variable '_',
     10 # from where it is taken later in the same expression.
     11 ABC=	${A B C:L:_:range:@i@$i=${_:[$i]}@}
     12 DEF=	${D E F:L:_:range:@i@$i=${_:[$i]}@}
     13 GHI=	${G H I:L:_:range:@i@$i=${_:[$i]}@}
     14 
     15 ABC.global:=	${ABC}		# is evaluated in the global scope
     16 .if ${ABC.global} != "1=A 2=B 3=C"
     17 .  error
     18 .endif
     19 
     20 .if ${DEF} != "1=D 2=E 3=F"	# is evaluated in the command line scope
     21 .  error
     22 .endif
     23 
     24 # Before var.c 1.1040 from 2023-02-09, the temporary variable '_' was placed
     25 # in the scope of the current evaluation, which meant that after the first
     26 # ':_' modifier had been evaluated in command line scope, all further
     27 # evaluations in global scope could not overwrite the variable '_' anymore,
     28 # as the command line scope takes precedence over the global scope.
     29 # The expression ${GHI} therefore evaluated to '1=D 2=E 3=F', reusing the
     30 # value of '_' from the previous evaluation in command line scope.
     31 GHI.global:=	${GHI}		# is evaluated in the global scope
     32 .if ${GHI.global} != "1=G 2=H 3=I"
     33 .  error
     34 .endif
     35 
     36 
     37 # In the parameterized form, having the variable name on the right side of
     38 # the = assignment operator looks confusing.  In almost all other situations,
     39 # the variable name is on the left-hand side of the = operator, therefore
     40 # '_=SAVED' looks like it would copy 'SAVED' to '_'.  Luckily, this modifier
     41 # is only rarely needed.
     42 .if ${1 2 3:L:@var@${var:_=SAVED:}@} != "1 2 3"
     43 .  error
     44 .elif ${SAVED} != "3"
     45 .  error
     46 .endif
     47 
     48 
     49 # The ':_' modifier takes a variable name as optional argument.  Before var.c
     50 # 1.867 from 2021-03-14, this variable name could refer to other variables,
     51 # such as in 'VAR.$p'.  It was not possible to refer to 'VAR.${param}' though,
     52 # as that form caused a parse error.  The cause for the parse error in
     53 # '${...:_=VAR.${param}}' is that the variable name is parsed in an ad-hoc
     54 # manner, stopping at the first ':', ')' or '}', without taking any nested
     55 # expressions into account.  Due to this inconsistency that short expressions
     56 # are possible but long expressions aren't, the name of the temporary variable
     57 # is no longer expanded.
     58 #
     59 # TODO: Warn about the unusual variable name '$S'.
     60 S=	INDIRECT_VARNAME
     61 .if ${value:L:@var@${var:_=$S}@} != "value"
     62 .  error
     63 .elif defined(INDIRECT_VARNAME)
     64 .  error
     65 .endif
     66 
     67 
     68 # When a variable using ':_' refers to another variable that also uses ':_',
     69 # the value of the temporary variable '_' from the inner expression leaks into
     70 # the evaluation of the outer expression.  If the expressions were evaluated
     71 # independently, the last word of the result would be outer_='outer' instead.
     72 INNER=	${inner:L:_:@i@$i inner_='$_'@}
     73 OUTER=	${outer:L:_:@o@$o ${INNER} outer_='$_'@}
     74 .if ${OUTER} != "outer inner inner_='inner' outer_='inner'"
     75 .endif
     76 
     77 
     78 all:
     79