xref: /src/usr.bin/make/unit-tests/dep-var.mk

# $NetBSD: dep-var.mk,v 1.3 2020/09/03 19:50:14 rillig Exp $
#
# Tests for variable references in dependency declarations.
#
# Uh oh, this feels so strange that probably nobody uses it. But it seems to
# be the only way to reach the lower half of SuffExpandChildren.

# XXX: The -dv log says:
#	Var_Parse: ${UNDEF1} with VARE_UNDEFERR|VARE_WANTRES
# but no error message is generated for this line.
# The variable expression ${UNDEF1} simply expands to an empty string.
all: ${UNDEF1}

# Using a double dollar in order to circumvent immediate variable expansion
# feels like unintended behavior.  At least the manual page says nothing at
# all about defined or undefined variables in dependency lines.
#
# At the point where the expression ${DEF2} is expanded, the variable DEF2
# is defined, so everything's fine.
all: $${DEF2} a-$${DEF2}-b

# This variable is not defined at all.
# XXX: The -dv log says:
#	Var_Parse: ${UNDEF3} with VARE_UNDEFERR|VARE_WANTRES
# but no error message is generated for this line, just like for UNDEF1.
# The variable expression ${UNDEF3} simply expands to an empty string.
all: $${UNDEF3}

# Try out how many levels of indirection are really expanded in dependency
# lines.
#
# The first level of indirection is the $$ in the dependency line.
# When the dependency line is parsed, it is resolved to the string
# "${INDIRECT_1}".  At this point, the dollar is just an ordinary character,
# waiting to be expanded at some later point.
#
# Later, in SuffExpandChildren, that expression is expanded again by calling
# Var_Parse, and this time, the result is the string "1-2-${INDIRECT_2}-2-1".
#
# This string is not expanded anymore by Var_Parse.  But there is another
# effect.  Now DirExpandCurly comes into play and expands the curly braces
# in this filename pattern, resulting in the string "1-2-$INDIRECT_2-2-1".
# As of 2020-09-03, the test dir.mk contains further details on this topic.
#
# Finally, this string is assigned to the local ${.TARGET} variable.  This
# variable is expanded when the shell command is generated.  At that point,
# the $I is expanded.  Since the variable I is not defined, it expands to
# the empty string.  This way, the final output is the string
# "1-2-NDIRECT_2-2-1", which differs from the actual name of the target.
# For exactly this reason, it is not recommended to use dollar signs in
# target names.
#
# The number of actual expansions is way more than one might expect,
# therefore this feature is probably not widely used.
#
all: 1-$${INDIRECT_1}-1
INDIRECT_1=	2-$${INDIRECT_2}-2
INDIRECT_2=	3-$${INDIRECT_3}-3
INDIRECT_3=	indirect

UNDEF1=	undef1
DEF2=	def2

undef1 def2 a-def2-b 1-2-$$INDIRECT_2-2-1:
	@echo ${.TARGET:Q}