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varmod-loop-varname.mk revision 1.2 
      1 # $NetBSD: varmod-loop-varname.mk,v 1.2 2021/04/04 13:35:26 rillig Exp $
      2 #
      3 # Tests for the first part of the variable modifier ':@var (a] ...@', which
      4 # contains the variable name to use during the loop.
      5 
      6 .MAKE.SAVE_DOLLARS=	yes
      7 
      8 
      9 # Before 2021-04-04, the name of the loop variable could be generated
     10 # dynamically.  There was no practical use-case for this.
     11 # Since var.c 1.907 from 2021-04-04, a '$' is no longer allowed in the
     12 # variable name.
     13 .if ${:Uone two three:@${:Ubar:S,b,v,}@+${var}+@} != "+one+ +two+ +three+"
     14 .  error
     15 .endif
     16 
     17 
     18 # ":::" is a very creative variable name, unlikely to occur in practice.
     19 # The expression ${\:\:\:} would not work since backslashes can only
     20 # be escaped in the modifiers, but not in the variable name, therefore
     21 # the extra indirection via the modifier ':U'.
     22 .if ${:U1 2 3:@:::@x${${:U\:\:\:}}y@} != "x1y x2y x3y"
     23 .  error
     24 .endif
     25 
     26 
     27 # "@@" is another creative variable name.
     28 .if ${:U1 2 3:@\@\@@x${@@}y@} != "x1y x2y x3y"
     29 .  error
     30 .endif
     31 
     32 
     33 # In extreme cases, even the backslash can be used as variable name.
     34 # It needs to be doubled though.
     35 .if ${:U1 2 3:@\\@x${${:Ux:S,x,\\,}}y@} != "x1y x2y x3y"
     36 .  error
     37 .endif
     38 
     39 
     40 # The variable name can technically be empty, and in this situation
     41 # the variable value cannot be accessed since the empty "variable"
     42 # is protected to always return an empty string.
     43 .if ${:U1 2 3:@@x${}y@} != "xy xy xy"
     44 .  error
     45 .endif
     46 
     47 
     48 # The :@ modifier resolves the variables from the replacement text once more
     49 # than expected.  In particular, it resolves _all_ variables from the scope,
     50 # and not only the loop variable (in this case v).
     51 SRCS=		source
     52 CFLAGS.source=	before
     53 ALL_CFLAGS:=	${SRCS:@src@${CFLAGS.${src}}@}	# note the ':='
     54 CFLAGS.source+=	after
     55 .if ${ALL_CFLAGS} != "before"
     56 .  error
     57 .endif
     58 
     59 
     60 # In the following example, the modifier ':@' expands the '$$' to '$'.  This
     61 # means that when the resulting expression is evaluated, these resulting '$'
     62 # will be interpreted as starting a subexpression.
     63 #
     64 # The d means direct reference, the i means indirect reference.
     65 RESOLVE=	${RES1} $${RES1}
     66 RES1=		1d${RES2} 1i$${RES2}
     67 RES2=		2d${RES3} 2i$${RES3}
     68 RES3=		3
     69 
     70 .if ${RESOLVE:@v@w${v}w@} != "w1d2d3w w2i3w w1i2d3 2i\${RES3}w w1d2d3 2i\${RES3} 1i\${RES2}w"
     71 .  error
     72 .endif
     73 
     74 
     75 # Until 2020-07-20, the variable name of the :@ modifier could end with one
     76 # or two dollar signs, which were silently ignored.
     77 # There's no point in allowing a dollar sign in that position.
     78 # Since var.c 1.907 from 2021-04-04, a '$' is no longer allowed in the
     79 # variable name.
     80 .if ${1 2 3:L:@v$@($v)@} != "(1) (2) (3)"
     81 .  error
     82 .else
     83 .  error
     84 .endif
     85 .if ${1 2 3:L:@v$$@($v)@} != "() () ()"
     86 .  error
     87 .else
     88 .  error
     89 .endif
     90 .if ${1 2 3:L:@v$$$@($v)@} != "() () ()"
     91 .  error
     92 .else
     93 .  error
     94 .endif
     95 
     96 
     97 # It may happen that there are nested :@ modifiers that use the same name for
     98 # for the loop variable.  These modifiers influence each other.
     99 #
    100 # As of 2020-10-18, the :@ modifier is implemented by actually setting a
    101 # variable in the scope of the expression and deleting it again after the
    102 # loop.  This is different from the .for loops, which substitute the variable
    103 # expression with ${:Uvalue}, leading to different unwanted side effects.
    104 #
    105 # To make the behavior more predictable, the :@ modifier should restore the
    106 # loop variable to the value it had before the loop.  This would result in
    107 # the string "1a b c1 2a b c2 3a b c3", making the two loops independent.
    108 .if ${:U1 2 3:@i@$i${:Ua b c:@i@$i@}${i:Uu}@} != "1a b cu 2a b cu 3a b cu"
    109 .  error
    110 .endif
    111 
    112 # During the loop, the variable is actually defined and nonempty.
    113 # If the loop were implemented in the same way as the .for loop, the variable
    114 # would be neither defined nor nonempty since all expressions of the form
    115 # ${var} would have been replaced with ${:Uword} before evaluating them.
    116 .if defined(var)
    117 .  error
    118 .endif
    119 .if ${:Uword:@var@${defined(var):?def:undef} ${empty(var):?empty:nonempty}@} \
    120     != "def nonempty"
    121 .  error
    122 .endif
    123 .if defined(var)
    124 .  error
    125 .endif
    126 
    127 all: .PHONY
    128