96 lines
3.9 KiB
Makefile
Executable File
96 lines
3.9 KiB
Makefile
Executable File
# $NetBSD: dep-var.mk,v 1.7 2023/02/13 21:01:46 rillig Exp $
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#
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# Tests for variable references in dependency declarations.
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#
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# Uh oh, this feels so strange that probably nobody uses it. But it seems to
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# be the only way to reach the lower half of SuffExpandChildren.
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.MAKEFLAGS: -dv
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# expect: Var_Parse: ${UNDEF1} (eval-defined)
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# Even though undefined expressions should lead to errors, no error message is
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# generated for this line. The variable expression ${UNDEF1} simply expands
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# to an empty string.
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all: ${UNDEF1}
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# Using a double dollar in order to circumvent immediate variable expansion
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# feels like unintended behavior. At least the manual page says nothing at
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# all about defined or undefined variables in dependency lines.
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#
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# At the point where the expression ${DEF2} is expanded, the variable DEF2
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# is defined, so everything's fine.
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all: $${DEF2} a-$${DEF2}-b
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# This variable is not defined at all.
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# XXX: The -dv log says later when expanding the sources of 'all':
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# Var_Parse: ${UNDEF3} (eval-defined)
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# but no error message is generated for this line, just like for UNDEF1.
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# The variable expression ${UNDEF3} simply expands to an empty string.
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all: $${UNDEF3}
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# Try out how many levels of indirection are really expanded in dependency
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# lines.
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#
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# The first level of indirection is the $$ in the dependency line.
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# When the dependency line is parsed, it is resolved to the string
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# "${INDIRECT_1}". At this point, the dollar is just an ordinary character,
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# waiting to be expanded at some later point.
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#
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# Later, in SuffExpandChildren, that expression is expanded again by calling
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# Var_Parse, and this time, the result is the string "1-2-${INDIRECT_2}-2-1".
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#
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# This string is not expanded anymore by Var_Parse. But there is another
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# effect. Now DirExpandCurly comes into play and expands the curly braces
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# in this filename pattern, resulting in the string "1-2-$INDIRECT_2-2-1".
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# As of 2020-09-03, the test dir.mk contains further details on this topic.
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#
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# Finally, this string is assigned to the local ${.TARGET} variable. This
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# variable is expanded when the shell command is generated. At that point,
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# the $I is expanded. Since the variable I is not defined, it expands to
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# the empty string. This way, the final output is the string
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# "1-2-NDIRECT_2-2-1", which differs from the actual name of the target.
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# For exactly this reason, it is not recommended to use dollar signs in
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# target names.
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#
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# The number of actual expansions is way more than one might expect,
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# therefore this feature is probably not widely used.
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#
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all: 1-$${INDIRECT_1}-1
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INDIRECT_1= 2-$${INDIRECT_2}-2
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INDIRECT_2= 3-$${INDIRECT_3}-3
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INDIRECT_3= indirect
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UNDEF1= undef1
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DEF2= def2
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# Cover the code in SuffExpandChildren that deals with malformed variable
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# expressions.
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#
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# This seems to be an edge case that never happens in practice, and it would
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# probably be appropriate to just error out in such a case.
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#
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# To trigger this piece of code, the variable name must contain "$)" or "$:"
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# or "$)" or "$$". Using "$:" does not work since the dependency line is
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# fully expanded before parsing, therefore any ':' in a target or source name
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# would be interpreted as a dependency operator instead.
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all: $$$$)
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# The $$INDIRECT in the following line is treated like the dependency of the
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# "all" target, that is, the "$$I" is first expanded to "$I", and in a second
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# round of expansion, the "$I" expands to nothing since the variable "I" is
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# undefined.
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#
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# Since 2020-09-13, this generates a parse error in lint mode (-dL), but not
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# in normal mode since ParseDependency does not handle any errors after
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# calling Var_Parse.
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# expect: Var_Parse: ${:U\$)}: (eval-defined)
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# expect: Var_Parse: $INDIRECT_2-2-1 $): (parse-only)
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# expect: Var_Parse: $): (parse-only)
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undef1 def2 a-def2-b 1-2-$$INDIRECT_2-2-1 ${:U\$)}:
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@echo ${.TARGET:Q}
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.MAKEFLAGS: -d0
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# XXX: Why is the exit status still 0, even though Parse_Error is called
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# with PARSE_FATAL in SuffExpandChildren?
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