1 # $NetBSD: dep-var.mk,v 1.5 2020/09/13 20:04:26 rillig Exp $
3 # Tests for variable references in dependency declarations.
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.
8 # XXX: The -dv log says:
9 # Var_Parse: ${UNDEF1} with VARE_UNDEFERR|VARE_WANTRES
10 # but no error message is generated for this line.
11 # The variable expression ${UNDEF1} simply expands to an empty string.
14 # Using a double dollar in order to circumvent immediate variable expansion
15 # feels like unintended behavior. At least the manual page says nothing at
16 # all about defined or undefined variables in dependency lines.
18 # At the point where the expression ${DEF2} is expanded, the variable DEF2
19 # is defined, so everything's fine.
20 all: $${DEF2} a-$${DEF2}-b
22 # This variable is not defined at all.
23 # XXX: The -dv log says:
24 # Var_Parse: ${UNDEF3} with VARE_UNDEFERR|VARE_WANTRES
25 # but no error message is generated for this line, just like for UNDEF1.
26 # The variable expression ${UNDEF3} simply expands to an empty string.
29 # Try out how many levels of indirection are really expanded in dependency
32 # The first level of indirection is the $$ in the dependency line.
33 # When the dependency line is parsed, it is resolved to the string
34 # "${INDIRECT_1}". At this point, the dollar is just an ordinary character,
35 # waiting to be expanded at some later point.
37 # Later, in SuffExpandChildren, that expression is expanded again by calling
38 # Var_Parse, and this time, the result is the string "1-2-${INDIRECT_2}-2-1".
40 # This string is not expanded anymore by Var_Parse. But there is another
41 # effect. Now DirExpandCurly comes into play and expands the curly braces
42 # in this filename pattern, resulting in the string "1-2-$INDIRECT_2-2-1".
43 # As of 2020-09-03, the test dir.mk contains further details on this topic.
45 # Finally, this string is assigned to the local ${.TARGET} variable. This
46 # variable is expanded when the shell command is generated. At that point,
47 # the $I is expanded. Since the variable I is not defined, it expands to
48 # the empty string. This way, the final output is the string
49 # "1-2-NDIRECT_2-2-1", which differs from the actual name of the target.
50 # For exactly this reason, it is not recommended to use dollar signs in
53 # The number of actual expansions is way more than one might expect,
54 # therefore this feature is probably not widely used.
56 all: 1-$${INDIRECT_1}-1
57 INDIRECT_1= 2-$${INDIRECT_2}-2
58 INDIRECT_2= 3-$${INDIRECT_3}-3
64 # Cover the code in SuffExpandChildren that deals with malformed variable
67 # This seems to be an edge case that never happens in practice, and it would
68 # probably be appropriate to just error out in such a case.
70 # To trigger this piece of code, the variable name must contain "$)" or "$:"
71 # or "$)" or "$$". Using "$:" does not work since the dependency line is
72 # fully expanded before parsing, therefore any ':' in a target or source name
73 # would be interpreted as a dependency operator instead.
76 # The $$INDIRECT in the following line is treated like the dependency of the
77 # "all" target, that is, the "$$I" is first expanded to "$I", and in a second
78 # round of expansion, the "$I" expands to nothing since the variable "I" is
81 # Since 2020-09-13, this generates a parse error in lint mode (-dL), but not
82 # in normal mode since ParseDoDependency does not handle any errors after
84 undef1 def2 a-def2-b 1-2-$$INDIRECT_2-2-1 ${:U\$)}:
87 # XXX: Why is the exit status still 0, even though Parse_Error is called
88 # with PARSE_FATAL in SuffExpandChildren?