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varmod-loop-varname.mk revision 1.3 
      1 # $NetBSD: varmod-loop-varname.mk,v 1.3 2021/11/30 23:52:19 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 # Force the test results to be independent of the default value of this
      7 # setting, which is 'yes' for NetBSD's usr.bin/make but 'no' for the bmake
      8 # distribution and pkgsrc/devel/bmake.
      9 .MAKE.SAVE_DOLLARS=	yes
     10 
     11 
     12 # Before 2021-04-04, the name of the loop variable could be generated
     13 # dynamically.  There was no practical use-case for this.
     14 # Since var.c 1.907 from 2021-04-04, a '$' is no longer allowed in the
     15 # variable name.
     16 .if ${:Uone two three:@${:Ubar:S,b,v,}@+${var}+@} != "+one+ +two+ +three+"
     17 .  error
     18 .endif
     19 
     20 
     21 # ":::" is a very creative variable name, unlikely to occur in practice.
     22 # The expression ${\:\:\:} would not work since backslashes can only
     23 # be escaped in the modifiers, but not in the variable name, therefore
     24 # the extra indirection via the modifier ':U'.
     25 .if ${:U1 2 3:@:::@x${${:U\:\:\:}}y@} != "x1y x2y x3y"
     26 .  error
     27 .endif
     28 
     29 
     30 # "@@" is another creative variable name.
     31 .if ${:U1 2 3:@\@\@@x${@@}y@} != "x1y x2y x3y"
     32 .  error
     33 .endif
     34 
     35 
     36 # In extreme cases, even the backslash can be used as variable name.
     37 # It needs to be doubled though.
     38 .if ${:U1 2 3:@\\@x${${:Ux:S,x,\\,}}y@} != "x1y x2y x3y"
     39 .  error
     40 .endif
     41 
     42 
     43 # The variable name can technically be empty, and in this situation
     44 # the variable value cannot be accessed since the empty "variable"
     45 # is protected to always return an empty string.
     46 .if ${:U1 2 3:@@x${}y@} != "xy xy xy"
     47 .  error
     48 .endif
     49 
     50 
     51 # The :@ modifier resolves the variables from the replacement text once more
     52 # than expected.  In particular, it resolves _all_ variables from the scope,
     53 # and not only the loop variable (in this case v).
     54 SRCS=		source
     55 CFLAGS.source=	before
     56 ALL_CFLAGS:=	${SRCS:@src@${CFLAGS.${src}}@}	# note the ':='
     57 CFLAGS.source+=	after
     58 .if ${ALL_CFLAGS} != "before"
     59 .  error
     60 .endif
     61 
     62 
     63 # In the following example, the modifier ':@' expands the '$$' to '$'.  This
     64 # means that when the resulting expression is evaluated, these resulting '$'
     65 # will be interpreted as starting a subexpression.
     66 #
     67 # The d means direct reference, the i means indirect reference.
     68 RESOLVE=	${RES1} $${RES1}
     69 RES1=		1d${RES2} 1i$${RES2}
     70 RES2=		2d${RES3} 2i$${RES3}
     71 RES3=		3
     72 
     73 .if ${RESOLVE:@v@w${v}w@} != "w1d2d3w w2i3w w1i2d3 2i\${RES3}w w1d2d3 2i\${RES3} 1i\${RES2}w"
     74 .  error
     75 .endif
     76 
     77 
     78 # Until 2020-07-20, the variable name of the :@ modifier could end with one
     79 # or two dollar signs, which were silently ignored.
     80 # There's no point in allowing a dollar sign in that position.
     81 # Since var.c 1.907 from 2021-04-04, a '$' is no longer allowed in the
     82 # variable name.
     83 .if ${1 2 3:L:@v$@($v)@} != "(1) (2) (3)"
     84 .  error
     85 .else
     86 .  error
     87 .endif
     88 .if ${1 2 3:L:@v$$@($v)@} != "() () ()"
     89 .  error
     90 .else
     91 .  error
     92 .endif
     93 .if ${1 2 3:L:@v$$$@($v)@} != "() () ()"
     94 .  error
     95 .else
     96 .  error
     97 .endif
     98 
     99 
    100 # It may happen that there are nested :@ modifiers that use the same name for
    101 # for the loop variable.  These modifiers influence each other.
    102 #
    103 # As of 2020-10-18, the :@ modifier is implemented by actually setting a
    104 # variable in the scope of the expression and deleting it again after the
    105 # loop.  This is different from the .for loops, which substitute the variable
    106 # expression with ${:Uvalue}, leading to different unwanted side effects.
    107 #
    108 # To make the behavior more predictable, the :@ modifier should restore the
    109 # loop variable to the value it had before the loop.  This would result in
    110 # the string "1a b c1 2a b c2 3a b c3", making the two loops independent.
    111 .if ${:U1 2 3:@i@$i${:Ua b c:@i@$i@}${i:Uu}@} != "1a b cu 2a b cu 3a b cu"
    112 .  error
    113 .endif
    114 
    115 # During the loop, the variable is actually defined and nonempty.
    116 # If the loop were implemented in the same way as the .for loop, the variable
    117 # would be neither defined nor nonempty since all expressions of the form
    118 # ${var} would have been replaced with ${:Uword} before evaluating them.
    119 .if defined(var)
    120 .  error
    121 .endif
    122 .if ${:Uword:@var@${defined(var):?def:undef} ${empty(var):?empty:nonempty}@} \
    123     != "def nonempty"
    124 .  error
    125 .endif
    126 .if defined(var)
    127 .  error
    128 .endif
    129 
    130 all: .PHONY
    131