1*ac7615f6Srillig# $NetBSD: varmod-loop.mk,v 1.23 2023/02/18 11:55:20 rillig Exp $ 21fb97e4bSrillig# 3*ac7615f6Srillig# Tests for the expression modifier ':@var@body@', which replaces each word of 4*ac7615f6Srillig# the expression with the expanded body, which may contain references to the 5*ac7615f6Srillig# variable 'var'. For example, '${1 2 3:L:@word@<${word}>@}' encloses each 6*ac7615f6Srillig# word in angle quotes, resulting in '<1> <2> <3>'. 7*ac7615f6Srillig# 8*ac7615f6Srillig# The variable name can be chosen freely, except that it must not contain a 9*ac7615f6Srillig# '$'. For simplicity and readability, variable names should only use the 10*ac7615f6Srillig# characters 'A-Za-z0-9'. 11*ac7615f6Srillig# 12*ac7615f6Srillig# The body may contain subexpressions in the form '${...}' or '$(...)'. These 13*ac7615f6Srillig# subexpressions differ from everywhere else in makefiles in that the parser 14*ac7615f6Srillig# only scans '${...}' for balanced '{' and '}', likewise for '$(...)'. Any 15*ac7615f6Srillig# other '$' is left as-is during parsing. Later, when the body is expanded 16*ac7615f6Srillig# for each word, each '$$' is interpreted as a single '$', and the remaining 17*ac7615f6Srillig# '$' are interpreted as expressions, like when evaluating a regular variable. 181fb97e4bSrillig 19a4748faaSrillig# Force the test results to be independent of the default value of this 20a4748faaSrillig# setting, which is 'yes' for NetBSD's usr.bin/make but 'no' for the bmake 21a4748faaSrillig# distribution and pkgsrc/devel/bmake. 221d4d4ae2Srillig.MAKE.SAVE_DOLLARS= yes 231d4d4ae2Srillig 24454079b0Srilligall: varname-overwriting-target 2591e13788Srilligall: mod-loop-dollar 261fb97e4bSrillig 27454079b0Srilligvarname-overwriting-target: 2891e13788Srillig # Even "@" works as a variable name since the variable is installed 2991e13788Srillig # in the "current" scope, which in this case is the one from the 30454079b0Srillig # target. Because of this, after the loop has finished, '$@' is 31454079b0Srillig # undefined. This is something that make doesn't expect, this may 32454079b0Srillig # even trigger an assertion failure somewhere. 3391e13788Srillig @echo :$@: :${:U1 2 3:@\@@x${@}y@}: :$@: 34f03f9dfbSrillig 3591e13788Srillig 363415e83bSrillig# Demonstrate that it is possible to generate dollar signs using the 3791e13788Srillig# :@ modifier. 3891e13788Srillig# 3991e13788Srillig# These are edge cases that could have resulted in a parse error as well 4091e13788Srillig# since the $@ at the end could have been interpreted as a variable, which 4191e13788Srillig# would mean a missing closing @ delimiter. 4291e13788Srilligmod-loop-dollar: 4391e13788Srillig @echo $@:${:U1:@word@${word}$@:Q}: 4491e13788Srillig @echo $@:${:U2:@word@$${word}$$@:Q}: 4591e13788Srillig @echo $@:${:U3:@word@$$${word}$$$@:Q}: 4691e13788Srillig @echo $@:${:U4:@word@$$$${word}$$$$@:Q}: 4791e13788Srillig @echo $@:${:U5:@word@$$$$${word}$$$$$@:Q}: 4891e13788Srillig @echo $@:${:U6:@word@$$$$$${word}$$$$$$@:Q}: 49990a4803Srillig 50990a4803Srillig# It may happen that there are nested :@ modifiers that use the same name for 51990a4803Srillig# for the loop variable. These modifiers influence each other. 52990a4803Srillig# 53f03f9dfbSrillig# As of 2020-10-18, the :@ modifier is implemented by actually setting a 544f7273d6Srillig# variable in the scope of the expression and deleting it again after the 55990a4803Srillig# loop. This is different from the .for loops, which substitute the variable 56990a4803Srillig# expression with ${:Uvalue}, leading to different unwanted side effects. 57990a4803Srillig# 58990a4803Srillig# To make the behavior more predictable, the :@ modifier should restore the 59990a4803Srillig# loop variable to the value it had before the loop. This would result in 60990a4803Srillig# the string "1a b c1 2a b c2 3a b c3", making the two loops independent. 61990a4803Srillig.if ${:U1 2 3:@i@$i${:Ua b c:@i@$i@}${i:Uu}@} != "1a b cu 2a b cu 3a b cu" 62990a4803Srillig. error 63990a4803Srillig.endif 64f03f9dfbSrillig 65f03f9dfbSrillig# During the loop, the variable is actually defined and nonempty. 66f03f9dfbSrillig# If the loop were implemented in the same way as the .for loop, the variable 67f03f9dfbSrillig# would be neither defined nor nonempty since all expressions of the form 68f03f9dfbSrillig# ${var} would have been replaced with ${:Uword} before evaluating them. 69f03f9dfbSrillig.if defined(var) 70f03f9dfbSrillig. error 71f03f9dfbSrillig.endif 72f03f9dfbSrillig.if ${:Uword:@var@${defined(var):?def:undef} ${empty(var):?empty:nonempty}@} \ 73f03f9dfbSrillig != "def nonempty" 74f03f9dfbSrillig. error 75f03f9dfbSrillig.endif 76f03f9dfbSrillig.if defined(var) 77f03f9dfbSrillig. error 78f03f9dfbSrillig.endif 79b925b94aSrillig 80b925b94aSrillig# Assignment using the ':=' operator, combined with the :@var@ modifier 81b925b94aSrillig# 82b925b94aSrillig8_DOLLARS= $$$$$$$$ 83b925b94aSrillig# This string literal is written with 8 dollars, and this is saved as the 84b925b94aSrillig# variable value. But as soon as this value is evaluated, it goes through 85b925b94aSrillig# Var_Subst, which replaces each '$$' with a single '$'. This could be 8612201810Srillig# prevented by VARE_EVAL_KEEP_DOLLAR, but that flag is usually removed 87413b6626Srillig# before expanding subexpressions. See ApplyModifier_Loop and 88413b6626Srillig# ParseModifierPart for examples. 89b925b94aSrillig# 90b925b94aSrillig.MAKEFLAGS: -dcp 91b925b94aSrilligUSE_8_DOLLARS= ${:U1:@var@${8_DOLLARS}@} ${8_DOLLARS} $$$$$$$$ 92b925b94aSrillig.if ${USE_8_DOLLARS} != "\$\$\$\$ \$\$\$\$ \$\$\$\$" 93b925b94aSrillig. error 94b925b94aSrillig.endif 95b925b94aSrillig# 96b925b94aSrilligSUBST_CONTAINING_LOOP:= ${USE_8_DOLLARS} 97413b6626Srillig# The ':=' assignment operator evaluates the variable value using the mode 98413b6626Srillig# VARE_KEEP_DOLLAR_UNDEF, which means that some dollar signs are preserved, 99413b6626Srillig# but not all. The dollar signs in the top-level expression and in the 100413b6626Srillig# indirect ${8_DOLLARS} are preserved. 101b925b94aSrillig# 102b925b94aSrillig# The variable modifier :@var@ does not preserve the dollar signs though, no 103b925b94aSrillig# matter in which context it is evaluated. What happens in detail is: 104b925b94aSrillig# First, the modifier part "${8_DOLLARS}" is parsed without expanding it. 105b925b94aSrillig# Next, each word of the value is expanded on its own, and at this moment 106413b6626Srillig# in ApplyModifier_Loop, the flag keepDollar is not passed down to 107b925b94aSrillig# ModifyWords, resulting in "$$$$" for the first word of USE_8_DOLLARS. 108b925b94aSrillig# 109b925b94aSrillig# The remaining words of USE_8_DOLLARS are not affected by any variable 110413b6626Srillig# modifier and are thus expanded with the flag keepDollar in action. 111b925b94aSrillig# The variable SUBST_CONTAINING_LOOP therefore gets assigned the raw value 112b925b94aSrillig# "$$$$ $$$$$$$$ $$$$$$$$". 113b925b94aSrillig# 114b925b94aSrillig# The variable expression in the condition then expands this raw stored value 115b925b94aSrillig# once, resulting in "$$ $$$$ $$$$". The effects from VARE_KEEP_DOLLAR no 116b925b94aSrillig# longer take place since they had only been active during the evaluation of 117b925b94aSrillig# the variable assignment. 118b925b94aSrillig.if ${SUBST_CONTAINING_LOOP} != "\$\$ \$\$\$\$ \$\$\$\$" 119b925b94aSrillig. error 120b925b94aSrillig.endif 121b925b94aSrillig.MAKEFLAGS: -d0 12288cc89a5Srillig 12388cc89a5Srillig# After looping over the words of the expression, the loop variable gets 12488cc89a5Srillig# undefined. The modifier ':@' uses an ordinary global variable for this, 12588cc89a5Srillig# which is different from the '.for' loop, which replaces ${var} with 12688cc89a5Srillig# ${:Uvalue} in the body of the loop. This choice of implementation detail 12788cc89a5Srillig# can be used for a nasty side effect. The expression ${:U:@VAR@@} evaluates 12888cc89a5Srillig# to an empty string, plus it undefines the variable 'VAR'. This is the only 12988cc89a5Srillig# possibility to undefine a global variable during evaluation. 13088cc89a5SrilligGLOBAL= before-global 13188cc89a5SrilligRESULT:= ${:U${GLOBAL} ${:U:@GLOBAL@@} ${GLOBAL:Uundefined}} 13288cc89a5Srillig.if ${RESULT} != "before-global undefined" 13388cc89a5Srillig. error 13488cc89a5Srillig.endif 13588cc89a5Srillig 13688cc89a5Srillig# The above side effect of undefining a variable from a certain scope can be 13788cc89a5Srillig# further combined with the otherwise undocumented implementation detail that 13888cc89a5Srillig# the argument of an '.if' directive is evaluated in cmdline scope. Putting 13988cc89a5Srillig# these together makes it possible to undefine variables from the cmdline 14088cc89a5Srillig# scope, something that is not possible in a straight-forward way. 14188cc89a5Srillig.MAKEFLAGS: CMDLINE=cmdline 14288cc89a5Srillig.if ${:U${CMDLINE}${:U:@CMDLINE@@}} != "cmdline" 14388cc89a5Srillig. error 14488cc89a5Srillig.endif 14588cc89a5Srillig# Now the cmdline variable got undefined. 14688cc89a5Srillig.if ${CMDLINE} != "cmdline" 14788cc89a5Srillig. error 14888cc89a5Srillig.endif 14988cc89a5Srillig# At this point, it still looks as if the cmdline variable were defined, 15088cc89a5Srillig# since the value of CMDLINE is still "cmdline". That impression is only 15188cc89a5Srillig# superficial though, the cmdline variable is actually deleted. To 15288cc89a5Srillig# demonstrate this, it is now possible to override its value using a global 15388cc89a5Srillig# variable, something that was not possible before: 15488cc89a5SrilligCMDLINE= global 15588cc89a5Srillig.if ${CMDLINE} != "global" 15688cc89a5Srillig. error 15788cc89a5Srillig.endif 15888cc89a5Srillig# Now undefine that global variable again, to get back to the original value. 15988cc89a5Srillig.undef CMDLINE 16088cc89a5Srillig.if ${CMDLINE} != "cmdline" 16188cc89a5Srillig. error 16288cc89a5Srillig.endif 16388cc89a5Srillig# What actually happened is that when CMDLINE was set by the '.MAKEFLAGS' 16488cc89a5Srillig# target in the cmdline scope, that same variable was exported to the 16588cc89a5Srillig# environment, see Var_SetWithFlags. 16688cc89a5Srillig.unexport CMDLINE 16788cc89a5Srillig.if ${CMDLINE} != "cmdline" 16888cc89a5Srillig. error 16988cc89a5Srillig.endif 17088cc89a5Srillig# The above '.unexport' has no effect since UnexportVar requires a global 17188cc89a5Srillig# variable of the same name to be defined, otherwise nothing is unexported. 17288cc89a5SrilligCMDLINE= global 17388cc89a5Srillig.unexport CMDLINE 17488cc89a5Srillig.undef CMDLINE 17588cc89a5Srillig.if ${CMDLINE} != "cmdline" 17688cc89a5Srillig. error 17788cc89a5Srillig.endif 17888cc89a5Srillig# This still didn't work since there must not only be a global variable, the 17988cc89a5Srillig# variable must be marked as exported as well, which it wasn't before. 18088cc89a5SrilligCMDLINE= global 18188cc89a5Srillig.export CMDLINE 18288cc89a5Srillig.unexport CMDLINE 18388cc89a5Srillig.undef CMDLINE 18488cc89a5Srillig.if ${CMDLINE:Uundefined} != "undefined" 18588cc89a5Srillig. error 18688cc89a5Srillig.endif 18788cc89a5Srillig# Finally the variable 'CMDLINE' from the cmdline scope is gone, and all its 18888cc89a5Srillig# traces from the environment are gone as well. To do that, a global variable 18988cc89a5Srillig# had to be defined and exported, something that is far from obvious. To 19088cc89a5Srillig# recap, here is the essence of the above story: 19188cc89a5Srillig.MAKEFLAGS: CMDLINE=cmdline # have a cmdline + environment variable 19288cc89a5Srillig.if ${:U:@CMDLINE@@}} # undefine cmdline, keep environment 19388cc89a5Srillig.endif 19488cc89a5SrilligCMDLINE= global # needed for deleting the environment 19588cc89a5Srillig.export CMDLINE # needed for deleting the environment 19688cc89a5Srillig.unexport CMDLINE # delete the environment 19788cc89a5Srillig.undef CMDLINE # delete the global helper variable 19888cc89a5Srillig.if ${CMDLINE:Uundefined} != "undefined" 19988cc89a5Srillig. error # 'CMDLINE' is gone now from all scopes 20088cc89a5Srillig.endif 20188cc89a5Srillig 20207908e3aSrillig 20307908e3aSrillig# In the loop body text of the ':@' modifier, a literal '$' is written as '$$', 20407908e3aSrillig# not '\$'. In the following example, each '$$' turns into a single '$', 20507908e3aSrillig# except for '$i', which is replaced with the then-current value '1' of the 20607908e3aSrillig# iteration variable. 20707908e3aSrillig# 208d357be07Srillig# See parse-var.mk, keyword 'BRACE_GROUP'. 20907908e3aSrilligall: varmod-loop-literal-dollar 21007908e3aSrilligvarmod-loop-literal-dollar: .PHONY 21107908e3aSrillig : ${:U1:@i@ t=$$(( $${t:-0} + $i ))@} 21207908e3aSrillig 21307908e3aSrillig 214bdd34607Srillig# When parsing the loop body, each '\$', '\@' and '\\' is unescaped to '$', 215d357be07Srillig# '@' and '\', respectively; all other backslashes are retained. 216bdd34607Srillig# 217bdd34607Srillig# In practice, the '$' is not escaped as '\$', as there is a second round of 218bdd34607Srillig# unescaping '$$' to '$' later when the loop body is expanded after setting the 219bdd34607Srillig# iteration variable. 220bdd34607Srillig# 221bdd34607Srillig# After the iteration variable has been set, the loop body is expanded with 222bdd34607Srillig# this unescaping, regardless of whether .MAKE.SAVE_DOLLARS is set or not: 223bdd34607Srillig# $$ a literal '$' 224bdd34607Srillig# $x, ${var}, $(var) a nested expression 225bdd34607Srillig# any other character itself 226bdd34607Srilligall: escape-modifier 227bdd34607Srilligescape-modifier: .PHONY 228bdd34607Srillig # In the first round, '\$ ' is unescaped to '$ ', and since the 229bdd34607Srillig # variable named ' ' is not defined, the expression '$ ' expands to an 230bdd34607Srillig # empty string. 231bdd34607Srillig # expect: : dollar=end 232bdd34607Srillig : ${:U1:@i@ dollar=\$ end@} 233bdd34607Srillig 234bdd34607Srillig # Like in other modifiers, '\ ' is preserved, since ' ' is not one of 235bdd34607Srillig # the characters that _must_ be escaped. 236bdd34607Srillig # expect: : backslash=\ end 237bdd34607Srillig : ${:U1:@i@ backslash=\ end@} 238bdd34607Srillig 239bdd34607Srillig # expect: : dollar=$ at=@ backslash=\ end 240bdd34607Srillig : ${:U1:@i@ dollar=\$\$ at=\@ backslash=\\ end@} 241bdd34607Srillig # expect: : dollar=$$ at=@@ backslash=\\ end 242bdd34607Srillig : ${:U1:@i@ dollar=\$\$\$\$ at=\@\@ backslash=\\\\ end@} 243bdd34607Srillig # expect: : dollar=$$ at=@@ backslash=\\ end 244bdd34607Srillig : ${:U1:@i@ dollar=$$$$ at=\@\@ backslash=\\\\ end@} 245bdd34607Srillig 24641515451Srilligall: .PHONY 247