122 lines
4.7 KiB
Makefile
122 lines
4.7 KiB
Makefile
# $NetBSD: varmod-match-escape.mk,v 1.13 2024/04/20 10:18:55 rillig Exp $
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#
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# As of 2020-08-01, the :M and :N modifiers interpret backslashes differently,
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# depending on whether there was an expression somewhere before the
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# first backslash or not. See ParseModifier_Match, "copy = true".
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#
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# Apart from the different and possibly confusing debug output, there is no
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# difference in behavior. When parsing the modifier text, only \{, \} and \:
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# are unescaped, and in the pattern matching these have the same meaning as
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# their plain variants '{', '}' and ':'. In the pattern matching from
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# Str_Match, only \*, \? or \[ would make a noticeable difference.
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.MAKEFLAGS: -dcv
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SPECIALS= \: : \\ * \*
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.if ${SPECIALS:M${:U}\:} != ${SPECIALS:M\:${:U}}
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. warning unexpected
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.endif
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# And now both cases combined: A single modifier with both an escaped ':'
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# as well as an expression that expands to a ':'.
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#
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# XXX: As of 2020-11-01, when an escaped ':' occurs before the
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# expression, the whole modifier text is subject to unescaping '\:' to ':',
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# before the expression is expanded. This means that the '\:' in
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# the expression is expanded as well, turning ${:U\:} into a simple
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# ${:U:}, which silently expands to an empty string, instead of generating
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# an error message.
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#
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# XXX: As of 2020-11-01, the modifier on the right-hand side of the
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# comparison is parsed differently though. First, the expression
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# is parsed, resulting in ':' and needSubst=true. After that, the escaped
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# ':' is seen, and this time, copy=true is not executed but stays copy=false.
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# Therefore the escaped ':' is kept as-is, and the final pattern becomes
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# ':\:'.
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#
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# If ParseModifier_Match had used the same parsing algorithm as Var_Subst,
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# both patterns would end up as '::'.
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#
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VALUES= : :: :\:
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.if ${VALUES:M\:${:U\:}} != ${VALUES:M${:U\:}\:}
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# expect+1: warning: XXX: Oops
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. warning XXX: Oops
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.endif
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.MAKEFLAGS: -d0
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# XXX: As of 2020-11-01, unlike all other variable modifiers, a '$' in the
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# :M and :N modifiers is written as '$$', not as '\$'. This is confusing,
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# undocumented and hopefully not used in practice.
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.if ${:U\$:M$$} != "\$"
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. error
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.endif
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# XXX: As of 2020-11-01, unlike all other variable modifiers, '\$' is not
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# parsed as an escaped '$'. Instead, ParseModifier_Match first scans for
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# the ':' at the end of the modifier, which results in the pattern '\$'.
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# No unescaping takes place since the pattern neither contained '\:' nor
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# '\{' nor '\}'. But the text is expanded, and a lonely '$' at the end
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# is silently discarded. The resulting expanded pattern is thus '\', that
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# is a single backslash.
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.if ${:U\$:M\$} != ""
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. error
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.endif
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# In lint mode, the case of a lonely '$' is covered with an error message.
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.MAKEFLAGS: -dL
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# expect+1: while evaluating "${:U\$:M\$} != """: Dollar followed by nothing
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.if ${:U\$:M\$} != ""
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. error
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.endif
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# The control flow of the pattern parser depends on the actual string that
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# is being matched. There needs to be either a test that shows a difference
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# in behavior, or a proof that the behavior does not depend on the actual
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# string.
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#
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# TODO: Str_Match("a-z]", "[a-z]")
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# TODO: Str_Match("012", "[0-]]")
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# TODO: Str_Match("[", "[[]")
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# TODO: Str_Match("]", "[]")
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# TODO: Str_Match("]", "[[-]]")
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# Demonstrate an inconsistency between positive and negative character lists
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# when the range ends with the character ']'.
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#
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# 'A' begins the range, 'B' is in the middle of the range, ']' ends the range,
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# 'a' is outside the range.
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WORDS= A A] A]] B B] B]] ] ]] ]]] a a] a]]
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# The ']' is part of the character range and at the same time ends the
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# character list.
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EXP.[A-]= A B ]
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# The first ']' is part of the character range and at the same time ends the
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# character list.
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EXP.[A-]]= A] B] ]]
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# The first ']' is part of the character range and at the same time ends the
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# character list.
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EXP.[A-]]]= A]] B]] ]]]
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# For negative character lists, the ']' ends the character range but does not
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# end the character list.
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# XXX: This is unnecessarily inconsistent but irrelevant in practice as there
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# is no practical need for a character range that ends at ']'.
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EXP.[^A-]= a
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EXP.[^A-]]= a
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EXP.[^A-]]]= a]
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.for pattern in [A-] [A-]] [A-]]] [^A-] [^A-]] [^A-]]]
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# expect+2: while evaluating variable "WORDS": warning: Unfinished character list in pattern '[A-]' of modifier ':M'
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# expect+1: while evaluating variable "WORDS": warning: Unfinished character list in pattern '[^A-]' of modifier ':M'
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. if ${WORDS:M${pattern}} != ${EXP.${pattern}}
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. warning ${pattern}: ${WORDS:M${pattern}} != ${EXP.${pattern}}
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. endif
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.endfor
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# In brackets, the backslash is just an ordinary character.
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# Outside brackets, it is an escape character for a few special characters.
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# TODO: Str_Match("\\", "[\\-]]")
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# TODO: Str_Match("-]", "[\\-]]")
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all:
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@:;
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