1 # $NetBSD: varmod-loop.mk,v 1.8 2020/11/12 00:40:55 rillig Exp $
3 # Tests for the :@var@...${var}...@ variable modifier.
5 .MAKE.SAVE_DOLLARS= yes
9 all: mod-loop-varname-dollar
12 # In the :@ modifier, the name of the loop variable can even be generated
13 # dynamically. There's no practical use-case for this, and hopefully nobody
14 # will ever depend on this, but technically it's possible.
15 # Therefore, in -dL mode, this is forbidden, see lint.mk.
17 @echo :${:Uone two three:@${:Ubar:S,b,v,}@+${var}+@:Q}:
19 # ":::" is a very creative variable name, unlikely in practice.
20 # The expression ${\:\:\:} would not work since backslashes can only
21 # be escaped in the modifiers, but not in the variable name.
22 @echo :${:U1 2 3:@:::@x${${:U\:\:\:}}y@}:
24 # "@@" is another creative variable name.
25 @echo :${:U1 2 3:@\@\@@x${@@}y@}:
27 # Even "@" works as a variable name since the variable is installed
28 # in the "current" scope, which in this case is the one from the
30 @echo :$@: :${:U1 2 3:@\@@x${@}y@}: :$@:
32 # In extreme cases, even the backslash can be used as variable name.
33 # It needs to be doubled though.
34 @echo :${:U1 2 3:@\\@x${${:Ux:S,x,\\,}}y@}:
36 # The variable name can technically be empty, and in this situation
37 # the variable value cannot be accessed since the empty variable is
38 # protected to always return an empty string.
39 @echo empty: :${:U1 2 3:@@x${}y@}:
41 # The :@ modifier resolves the variables a little more often than expected.
42 # In particular, it resolves _all_ variables from the context, and not only
43 # the loop variable (in this case v).
45 # The d means direct reference, the i means indirect reference.
46 RESOLVE= ${RES1} $${RES1}
47 RES1= 1d${RES2} 1i$${RES2}
48 RES2= 2d${RES3} 2i$${RES3}
52 @echo $@:${RESOLVE:@v@w${v}w@:Q}:
54 # Until 2020-07-20, the variable name of the :@ modifier could end with one
55 # or two dollar signs, which were silently ignored.
56 # There's no point in allowing a dollar sign in that position.
57 mod-loop-varname-dollar:
58 @echo $@:${1 2 3:L:@v$@($v)@:Q}.
59 @echo $@:${1 2 3:L:@v$$@($v)@:Q}.
60 @echo $@:${1 2 3:L:@v$$$@($v)@:Q}.
62 # Demonstrate that it is possible to generate dollar signs using the
65 # These are edge cases that could have resulted in a parse error as well
66 # since the $@ at the end could have been interpreted as a variable, which
67 # would mean a missing closing @ delimiter.
69 @echo $@:${:U1:@word@${word}$@:Q}:
70 @echo $@:${:U2:@word@$${word}$$@:Q}:
71 @echo $@:${:U3:@word@$$${word}$$$@:Q}:
72 @echo $@:${:U4:@word@$$$${word}$$$$@:Q}:
73 @echo $@:${:U5:@word@$$$$${word}$$$$$@:Q}:
74 @echo $@:${:U6:@word@$$$$$${word}$$$$$$@:Q}:
76 # It may happen that there are nested :@ modifiers that use the same name for
77 # for the loop variable. These modifiers influence each other.
79 # As of 2020-10-18, the :@ modifier is implemented by actually setting a
80 # variable in the context of the expression and deleting it again after the
81 # loop. This is different from the .for loops, which substitute the variable
82 # expression with ${:Uvalue}, leading to different unwanted side effects.
84 # To make the behavior more predictable, the :@ modifier should restore the
85 # loop variable to the value it had before the loop. This would result in
86 # the string "1a b c1 2a b c2 3a b c3", making the two loops independent.
87 .if ${:U1 2 3:@i@$i${:Ua b c:@i@$i@}${i:Uu}@} != "1a b cu 2a b cu 3a b cu"
91 # During the loop, the variable is actually defined and nonempty.
92 # If the loop were implemented in the same way as the .for loop, the variable
93 # would be neither defined nor nonempty since all expressions of the form
94 # ${var} would have been replaced with ${:Uword} before evaluating them.
98 .if ${:Uword:@var@${defined(var):?def:undef} ${empty(var):?empty:nonempty}@} \
106 # Assignment using the ':=' operator, combined with the :@var@ modifier
109 # This string literal is written with 8 dollars, and this is saved as the
110 # variable value. But as soon as this value is evaluated, it goes through
111 # Var_Subst, which replaces each '$$' with a single '$'. This could be
112 # prevented by VARE_KEEP_DOLLAR, but that flag is usually removed before
113 # expanding subexpressions. See ApplyModifier_Loop and ParseModifierPart
117 USE_8_DOLLARS= ${:U1:@var@${8_DOLLARS}@} ${8_DOLLARS} $$$$$$$$
118 .if ${USE_8_DOLLARS} != "\$\$\$\$ \$\$\$\$ \$\$\$\$"
122 SUBST_CONTAINING_LOOP:= ${USE_8_DOLLARS}
123 # The ':=' assignment operator evaluates the variable value using the flag
124 # VARE_KEEP_DOLLAR, which means that some dollar signs are preserved, but not
125 # all. The dollar signs in the top-level expression and in the indirect
126 # ${8_DOLLARS} are preserved.
128 # The variable modifier :@var@ does not preserve the dollar signs though, no
129 # matter in which context it is evaluated. What happens in detail is:
130 # First, the modifier part "${8_DOLLARS}" is parsed without expanding it.
131 # Next, each word of the value is expanded on its own, and at this moment
132 # in ApplyModifier_Loop, the VARE_KEEP_DOLLAR flag is not passed down to
133 # ModifyWords, resulting in "$$$$" for the first word of USE_8_DOLLARS.
135 # The remaining words of USE_8_DOLLARS are not affected by any variable
136 # modifier and are thus expanded with the flag VARE_KEEP_DOLLAR in action.
137 # The variable SUBST_CONTAINING_LOOP therefore gets assigned the raw value
138 # "$$$$ $$$$$$$$ $$$$$$$$".
140 # The variable expression in the condition then expands this raw stored value
141 # once, resulting in "$$ $$$$ $$$$". The effects from VARE_KEEP_DOLLAR no
142 # longer take place since they had only been active during the evaluation of
143 # the variable assignment.
144 .if ${SUBST_CONTAINING_LOOP} != "\$\$ \$\$\$\$ \$\$\$\$"