291 lines
8.5 KiB
Makefile
291 lines
8.5 KiB
Makefile
# $NetBSD: var-op-expand.mk,v 1.17 2022/09/08 20:23:45 rillig Exp $
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#
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# Tests for the := variable assignment operator, which expands its
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# right-hand side.
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#
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# See also:
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# varname-dot-make-save_dollars.mk
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# Force the test results to be independent of the default value of this
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# setting, which is 'yes' for NetBSD's usr.bin/make but 'no' for the bmake
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# distribution and pkgsrc/devel/bmake.
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.MAKE.SAVE_DOLLARS:= yes
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# If the right-hand side does not contain a dollar sign, the ':=' assignment
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# operator has the same effect as the '=' assignment operator.
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VAR:= value
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.if ${VAR} != "value"
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. error
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.endif
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# When a ':=' assignment is performed, its right-hand side is evaluated and
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# expanded as far as possible. Contrary to other situations, '$$' and
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# variable expressions based on undefined variables are preserved though.
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#
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# Whether a variable expression is undefined or not is determined at the end
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# of evaluating the expression. The consequence is that ${:Ufallback} expands
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# to "fallback"; initially this expression is undefined since it is based on
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# the variable named "", which is guaranteed to be never defined, but at the
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# end of evaluating the expression ${:Ufallback}, the modifier ':U' has turned
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# the expression into a defined expression.
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# literal dollar signs
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VAR:= $$ $$$$ $$$$$$$$
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.if ${VAR} != "\$ \$\$ \$\$\$\$"
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. error
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.endif
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# reference to a variable containing literal dollar signs
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REF= $$ $$$$ $$$$$$$$
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VAR:= ${REF}
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REF= too late
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.if ${VAR} != "\$ \$\$ \$\$\$\$"
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. error
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.endif
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# reference to an undefined variable
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.undef UNDEF
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VAR:= <${UNDEF}>
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.if ${VAR} != "<>"
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. error
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.endif
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UNDEF= after
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.if ${VAR} != "<after>"
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. error
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.endif
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# reference to a variable whose name is computed from another variable
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REF2= referred to
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REF= REF2
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VAR:= ${${REF}}
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REF= too late
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.if ${VAR} != "referred to"
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. error
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.endif
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# expression with an indirect modifier referring to an undefined variable
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.undef UNDEF
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VAR:= ${:${UNDEF}}
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.if ${VAR} != ""
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. error
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.endif
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UNDEF= Uwas undefined
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.if ${VAR} != "was undefined"
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. error
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.endif
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# expression with an indirect modifier referring to another variable that
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# in turn refers to an undefined variable
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#
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# XXX: Even though this is a ':=' assignment, the '${UNDEF}' in the part of
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# the variable modifier is not preserved. To preserve it, ParseModifierPart
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# would have to call VarSubstExpr somehow since this is the only piece of
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# code that takes care of this global variable.
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.undef UNDEF
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REF= U${UNDEF}
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#.MAKEFLAGS: -dv
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VAR:= ${:${REF}}
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#.MAKEFLAGS: -d0
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REF= too late
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UNDEF= Uwas undefined
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.if ${VAR} != ""
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. error
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.endif
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# In variable assignments using the ':=' operator, undefined variables are
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# preserved, no matter how indirectly they are referenced.
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.undef REF3
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REF2= <${REF3}>
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REF= ${REF2}
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VAR:= ${REF}
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.if ${VAR} != "<>"
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. error
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.endif
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REF3= too late
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.if ${VAR} != "<too late>"
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. error
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.endif
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# In variable assignments using the ':=' operator, '$$' are preserved, no
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# matter how indirectly they are referenced.
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REF2= REF2:$$ $$$$
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REF= REF:$$ $$$$ ${REF2}
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VAR:= VAR:$$ $$$$ ${REF}
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.if ${VAR} != "VAR:\$ \$\$ REF:\$ \$\$ REF2:\$ \$\$"
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. error
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.endif
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# In variable assignments using the ':=' operator, '$$' are preserved in the
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# expressions of the top level, but not in expressions that are nested.
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VAR:= top:$$ ${:Unest1\:\$\$} ${:Unest2${:U\:\$\$}}
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.if ${VAR} != "top:\$ nest1:\$ nest2:\$"
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. error
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.endif
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# In variable assignments using the ':=' operator, there may be expressions
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# containing variable modifiers, and these modifiers may refer to other
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# variables. These referred-to variables are expanded at the time of
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# assignment. The undefined variables are kept as-is and are later expanded
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# when evaluating the condition.
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#
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# Contrary to the assignment operator '=', the assignment operator ':='
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# consumes the '$' from modifier parts.
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REF.word= 1:$$ 2:$$$$ 4:$$$$$$$$
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.undef REF.undef
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VAR:= ${:Uword undef:@word@${REF.${word}}@}, direct: ${REF.word} ${REF.undef}
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REF.word= word.after
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REF.undef= undef.after
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.if ${VAR} != "1:2:\$ 4:\$\$ undef.after, direct: 1:\$ 2:\$\$ 4:\$\$\$\$ undef.after"
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. error
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.endif
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# Just for comparison, the previous example using the assignment operator '='
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# instead of ':='. The right-hand side of the assignment is not evaluated at
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# the time of assignment but only later, when ${VAR} appears in the condition.
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#
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# At that point, both REF.word and REF.undef are defined.
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REF.word= 1:$$ 2:$$$$ 4:$$$$$$$$
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.undef REF.undef
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VAR= ${:Uword undef:@word@${REF.${word}}@}, direct: ${REF.word} ${REF.undef}
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REF.word= word.after
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REF.undef= undef.after
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.if ${VAR} != "word.after undef.after, direct: word.after undef.after"
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. error
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.endif
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# Between var.c 1.42 from 2000-05-11 and before parse.c 1.520 from 2020-12-27,
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# if the variable name in a ':=' assignment referred to an undefined variable,
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# there were actually 2 assignments to different variables:
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#
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# Global["VAR_SUBST_${UNDEF}"] = ""
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# Global["VAR_SUBST_"] = ""
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#
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# The variable name with the empty value actually included a dollar sign.
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# Variable names with dollars are not used in practice.
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#
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# It might be a good idea to forbid undefined variables on the left-hand side
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# of a variable assignment.
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.undef UNDEF
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VAR_ASSIGN_${UNDEF}= assigned by '='
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VAR_SUBST_${UNDEF}:= assigned by ':='
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.if ${VAR_ASSIGN_} != "assigned by '='"
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. error
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.endif
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.if defined(${:UVAR_SUBST_\${UNDEF\}})
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. error
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.endif
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.if ${VAR_SUBST_} != "assigned by ':='"
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. error
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.endif
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# The following test case demonstrates that the variable 'LATER' is preserved
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# in the ':=' assignment since the variable 'LATER' is not yet defined.
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# After the assignment to 'LATER', evaluating the variable 'INDIRECT'
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# evaluates 'LATER' as well.
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#
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.undef LATER
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INDIRECT:= ${LATER:S,value,replaced,}
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.if ${INDIRECT} != ""
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. error
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.endif
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LATER= late-value
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.if ${INDIRECT} != "late-replaced"
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. error
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.endif
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# Same as the test case above, except for the additional modifier ':tl' when
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# evaluating the variable 'INDIRECT'. Nothing surprising here.
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.undef LATER
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.undef later
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INDIRECT:= ${LATER:S,value,replaced,}
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.if ${INDIRECT:tl} != ""
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. error
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.endif
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LATER= uppercase-value
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later= lowercase-value
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.if ${INDIRECT:tl} != "uppercase-replaced"
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. error
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.endif
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# Similar to the two test cases above, the situation gets a bit more involved
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# here, due to the double indirection. The variable 'indirect' is supposed to
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# be the lowercase version of the variable 'INDIRECT'.
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#
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# The assignment operator ':=' for the variable 'INDIRECT' could be a '=' as
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# well, it wouldn't make a difference in this case. The crucial detail is the
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# assignment operator ':=' for the variable 'indirect'. During this
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# assignment, the variable modifier ':S,value,replaced,' is converted to
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# lowercase, which turns 'S' into 's', thus producing an unknown modifier.
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# In this case, make issues a warning, but in cases where the modifier
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# includes a '=', the modifier would be interpreted as a SysV-style
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# substitution like '.c=.o', and make would not issue a warning, leading to
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# silent unexpected behavior.
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#
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# As of 2021-11-20, the actual behavior is unexpected. Fixing it is not
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# trivial. When the assignment to 'indirect' takes place, the expressions
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# from the nested expression could be preserved, like this:
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#
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# Start with:
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#
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# indirect:= ${INDIRECT:tl}
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#
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# Since INDIRECT is defined, expand it, remembering that the modifier
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# ':tl' must still be applied to the final result.
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#
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# indirect:= ${LATER:S,value,replaced,} \
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# OK \
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# ${LATER:value=sysv}
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#
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# The variable 'LATER' is not defined. An idea may be to append the
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# remaining modifier ':tl' to each expression that is starting with an
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# undefined variable, resulting in:
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#
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# indirect:= ${LATER:S,value,replaced,:tl} \
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# OK \
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# ${LATER:value=sysv:tl}
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#
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# This would work for the first expression. The second expression ends
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# with the SysV modifier ':from=to', and when this modifier is parsed,
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# it consumes all characters until the end of the expression, which in
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# this case would replace the suffix 'value' with the literal 'sysv:tl',
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# ignoring that the ':tl' was intended to be an additional modifier.
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#
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# Due to all of this, this surprising behavior is not easy to fix.
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#
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.undef LATER
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.undef later
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INDIRECT:= ${LATER:S,value,replaced,} OK ${LATER:value=sysv}
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indirect:= ${INDIRECT:tl}
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# expect+1: Unknown modifier "s,value,replaced,"
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.if ${indirect} != " ok "
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. error
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.else
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. warning XXX Neither branch should be taken.
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.endif
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LATER= uppercase-value
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later= lowercase-value
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# expect+1: Unknown modifier "s,value,replaced,"
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.if ${indirect} != "uppercase-replaced ok uppercase-sysv"
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. warning XXX Neither branch should be taken.
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.else
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. error
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.endif
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all:
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@:;
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