1# $NetBSD: dep-var.mk,v 1.13 2025/01/14 21:23:17 rillig Exp $ 2# 3# Tests for variable references in dependency declarations. 4# 5# Uh oh, this feels so strange that probably nobody uses it. But it seems to 6# be the only way to reach the lower half of SuffExpandChildren. 7 8.MAKEFLAGS: -dv 9 10# In a dependency line, an undefined expressions expands to an empty string. 11# expect: Var_Parse: ${UNDEF1} (eval) 12all: ${UNDEF1} 13 14# Using a double dollar in order to circumvent immediate expression expansion 15# feels like unintended behavior. At least the manual page says nothing at 16# all about defined or undefined variables in dependency lines. 17# 18# At the point where the expression ${DEF2} is expanded, the variable DEF2 19# is defined, so everything's fine. 20all: $${DEF2} a-$${DEF2}-b 21 22# This variable is neither defined now nor later. 23all: $${UNDEF3} 24 25# Try out how many levels of indirection are really expanded in dependency 26# lines. 27# 28# The first level of indirection is the $$ in the dependency line. 29# When the dependency line is parsed, it is resolved to the string 30# "${INDIRECT_1}". At this point, the dollar is just an ordinary character, 31# waiting to be expanded at some later point. 32# 33# Later, in SuffExpandChildren, that expression is expanded again by calling 34# Var_Parse, and this time, the result is the string "1-2-${INDIRECT_2}-2-1". 35# 36# This string is not expanded anymore by Var_Parse. But there is another 37# effect. Now DirExpandCurly comes into play and expands the curly braces 38# in this filename pattern, resulting in the string "1-2-$INDIRECT_2-2-1". 39# As of 2020-09-03, the test dir.mk contains further details on this topic. 40# 41# Finally, this string is assigned to the local ${.TARGET} variable. This 42# variable is expanded when the shell command is generated. At that point, 43# the $I is expanded. Since the variable I is not defined, it expands to 44# the empty string. This way, the final output is the string 45# "1-2-NDIRECT_2-2-1", which differs from the actual name of the target. 46# For exactly this reason, it is not recommended to use dollar signs in 47# target names. 48# 49# The number of actual expansions is way more than one might expect, 50# therefore this feature is probably not widely used. 51# 52all: 1-$${INDIRECT_1}-1 53INDIRECT_1= 2-$${INDIRECT_2}-2 54INDIRECT_2= 3-$${INDIRECT_3}-3 55INDIRECT_3= indirect 56 57UNDEF1= undef1 58DEF2= def2 59 60# Cover the code in SuffExpandChildren that deals with malformed 61# expressions. 62# 63# This seems to be an edge case that never happens in practice, and it would 64# probably be appropriate to just error out in such a case. 65# 66# To trigger this piece of code, the variable name must contain "$)" or "$:" 67# or "$)" or "$$". Using "$:" does not work since the dependency line is 68# fully expanded before parsing, therefore any ':' in a target or source name 69# would be interpreted as a dependency operator instead. 70all: $$$$) 71 72# The $$INDIRECT in the following line is treated like the dependency of the 73# "all" target, that is, the "$$I" is first expanded to "$I", and in a second 74# round of expansion, the "$I" expands to nothing since the variable "I" is 75# undefined. 76# 77# Since 2020-09-13, this generates a parse error in lint mode (-dL), but not 78# in normal mode since ParseDependency does not handle any errors after 79# calling Var_Parse. 80# expect: Var_Parse: ${:U\$)}: (eval) 81# expect: Var_Parse: $INDIRECT_2-2-1 $): (parse) 82# expect: Var_Parse: $): (parse) 83undef1 def2 a-def2-b 1-2-$$INDIRECT_2-2-1 ${:U\$)}: 84 @echo ${.TARGET:Q} 85 86.MAKEFLAGS: -d0 87