1# $NetBSD: varmod-loop.mk,v 1.8 2020/11/12 00:40:55 rillig Exp $ 2# 3# Tests for the :@var@...${var}...@ variable modifier. 4 5.MAKE.SAVE_DOLLARS= yes 6 7all: mod-loop-varname 8all: mod-loop-resolve 9all: mod-loop-varname-dollar 10all: mod-loop-dollar 11 12# In the :@ modifier, the name of the loop variable can even be generated 13# dynamically. There's no practical use-case for this, and hopefully nobody 14# will ever depend on this, but technically it's possible. 15# Therefore, in -dL mode, this is forbidden, see lint.mk. 16mod-loop-varname: 17 @echo :${:Uone two three:@${:Ubar:S,b,v,}@+${var}+@:Q}: 18 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@}: 23 24 # "@@" is another creative variable name. 25 @echo :${:U1 2 3:@\@\@@x${@@}y@}: 26 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 29 # target. 30 @echo :$@: :${:U1 2 3:@\@@x${@}y@}: :$@: 31 32 # In extreme cases, even the backslash can be used as variable name. 33 # It needs to be doubled though. 34 @echo :${:U1 2 3:@\\@x${${:Ux:S,x,\\,}}y@}: 35 36 # The variable name can technically be empty, and in this situation 37 # the variable value cannot be accessed since the empty variable is 38 # protected to always return an empty string. 39 @echo empty: :${:U1 2 3:@@x${}y@}: 40 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). 44# 45# The d means direct reference, the i means indirect reference. 46RESOLVE= ${RES1} $${RES1} 47RES1= 1d${RES2} 1i$${RES2} 48RES2= 2d${RES3} 2i$${RES3} 49RES3= 3 50 51mod-loop-resolve: 52 @echo $@:${RESOLVE:@v@w${v}w@:Q}: 53 54# Until 2020-07-20, the variable name of the :@ modifier could end with one 55# or two dollar signs, which were silently ignored. 56# There's no point in allowing a dollar sign in that position. 57mod-loop-varname-dollar: 58 @echo $@:${1 2 3:L:@v$@($v)@:Q}. 59 @echo $@:${1 2 3:L:@v$$@($v)@:Q}. 60 @echo $@:${1 2 3:L:@v$$$@($v)@:Q}. 61 62# Demonstrate that it is possible to generate dollar signs using the 63# :@ modifier. 64# 65# These are edge cases that could have resulted in a parse error as well 66# since the $@ at the end could have been interpreted as a variable, which 67# would mean a missing closing @ delimiter. 68mod-loop-dollar: 69 @echo $@:${:U1:@word@${word}$@:Q}: 70 @echo $@:${:U2:@word@$${word}$$@:Q}: 71 @echo $@:${:U3:@word@$$${word}$$$@:Q}: 72 @echo $@:${:U4:@word@$$$${word}$$$$@:Q}: 73 @echo $@:${:U5:@word@$$$$${word}$$$$$@:Q}: 74 @echo $@:${:U6:@word@$$$$$${word}$$$$$$@:Q}: 75 76# It may happen that there are nested :@ modifiers that use the same name for 77# for the loop variable. These modifiers influence each other. 78# 79# As of 2020-10-18, the :@ modifier is implemented by actually setting a 80# variable in the context of the expression and deleting it again after the 81# loop. This is different from the .for loops, which substitute the variable 82# expression with ${:Uvalue}, leading to different unwanted side effects. 83# 84# To make the behavior more predictable, the :@ modifier should restore the 85# loop variable to the value it had before the loop. This would result in 86# the string "1a b c1 2a b c2 3a b c3", making the two loops independent. 87.if ${:U1 2 3:@i@$i${:Ua b c:@i@$i@}${i:Uu}@} != "1a b cu 2a b cu 3a b cu" 88. error 89.endif 90 91# During the loop, the variable is actually defined and nonempty. 92# If the loop were implemented in the same way as the .for loop, the variable 93# would be neither defined nor nonempty since all expressions of the form 94# ${var} would have been replaced with ${:Uword} before evaluating them. 95.if defined(var) 96. error 97.endif 98.if ${:Uword:@var@${defined(var):?def:undef} ${empty(var):?empty:nonempty}@} \ 99 != "def nonempty" 100. error 101.endif 102.if defined(var) 103. error 104.endif 105 106# Assignment using the ':=' operator, combined with the :@var@ modifier 107# 1088_DOLLARS= $$$$$$$$ 109# This string literal is written with 8 dollars, and this is saved as the 110# variable value. But as soon as this value is evaluated, it goes through 111# Var_Subst, which replaces each '$$' 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 114# for examples. 115# 116.MAKEFLAGS: -dcp 117USE_8_DOLLARS= ${:U1:@var@${8_DOLLARS}@} ${8_DOLLARS} $$$$$$$$ 118.if ${USE_8_DOLLARS} != "\$\$\$\$ \$\$\$\$ \$\$\$\$" 119. error 120.endif 121# 122SUBST_CONTAINING_LOOP:= ${USE_8_DOLLARS} 123# The ':=' assignment operator evaluates the variable value using the flag 124# VARE_KEEP_DOLLAR, which means that some dollar signs are preserved, but not 125# all. The dollar signs in the top-level expression and in the indirect 126# ${8_DOLLARS} are preserved. 127# 128# The variable modifier :@var@ does not preserve the dollar signs though, no 129# matter in which context it is evaluated. What happens in detail is: 130# First, the modifier part "${8_DOLLARS}" is parsed without expanding it. 131# Next, each word of the value is expanded on its own, and at this moment 132# in ApplyModifier_Loop, the VARE_KEEP_DOLLAR flag is not passed down to 133# ModifyWords, resulting in "$$$$" for the first word of USE_8_DOLLARS. 134# 135# The remaining words of USE_8_DOLLARS are not affected by any variable 136# modifier and are thus expanded with the flag VARE_KEEP_DOLLAR in action. 137# The variable SUBST_CONTAINING_LOOP therefore gets assigned the raw value 138# "$$$$ $$$$$$$$ $$$$$$$$". 139# 140# The variable expression in the condition then expands this raw stored value 141# once, resulting in "$$ $$$$ $$$$". 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} != "\$\$ \$\$\$\$ \$\$\$\$" 145. error 146.endif 147.MAKEFLAGS: -d0 148