1 files changed, 131 insertions, 0 deletions
diff --git a/contrib/bmake/unit-tests/char-005c-reverse-solidus.mk b/contrib/bmake/unit-tests/char-005c-reverse-solidus.mk
new file mode 100644
index 000000000000..7a151ac46322
--- /dev/null
+++ b/contrib/bmake/unit-tests/char-005c-reverse-solidus.mk
@@ -0,0 +1,131 @@
+# $NetBSD: char-005c-reverse-solidus.mk,v 1.2 2025/06/29 11:27:21 rillig Exp $
+#
+# Tests for the character U+005C "REVERSE SOLIDUS".
+#
+# See also:
+#	TODO
+#	TODO
+#	TODO
+
+# TODO: Where is this character used normally?
+# TODO: What are the edge cases?
+
+# TODO: escape '#' in lines
+# TODO: escape '#' in comments
+# TODO: escape ':' in modifiers
+# TODO: escape any character in condition strings
+
+# begin https://gnats.netbsd.org/46139
+
+# Too see the details of parsing, uncomment the following line.
+#.MAKEFLAGS: -dcpv
+
+# This backslash is treated as a line continuation.
+# It does not end up in the variable value.
+LINE_CONTINUATION=foo\
+# This line is still part of the variable assignment
+.if ${LINE_CONTINUATION:C,[^a-z],<>,gW} != "foo"
+.  error
+.endif
+
+# The variable value contains two backslashes.
+TWO_BACKSLASHES_AT_EOL=foo\\
+.if ${TWO_BACKSLASHES_AT_EOL:C,[^a-z],<>,gW} != "foo<><>"
+.  error
+.endif
+
+TRAILING_WHITESPACE=foo\ # trailing space
+.if ${TRAILING_WHITESPACE:C,[^a-z],<>,gW} != "foo<><>"
+.  error
+.endif
+
+# The simplest was to produce a single backslash is the :U modifier.
+BACKSLASH=	${:U\\}
+.if ${BACKSLASH} != "\\"
+.  error
+.endif
+BACKSLASH_C=	${:U1:C,.,\\,}
+.if ${BACKSLASH_C} != "\\"
+.  error
+.endif
+
+# expect+5: Unclosed expression, expecting "}" for modifier "Mx\}"
+# At the point where the unclosed expression is detected, the ":M" modifier
+# has been applied to the expression.  Its pattern is "x}", which doesn't
+# match the single backslash.
+# expect: while evaluating variable "BACKSLASH" with value ""
+.if ${BACKSLASH:Mx\}
+.  error
+.else
+.  error
+.endif
+
+# expect+1: Unclosed expression, expecting "}" for modifier "Mx\\}"
+.if ${BACKSLASH:Mx\\}
+.  error
+.else
+.  error
+.endif
+
+# expect+1: Unclosed expression, expecting "}" for modifier "Mx\\\\\\\\}"
+.if ${BACKSLASH:Mx\\\\\\\\}
+.  error
+.else
+.  error
+.endif
+
+# Adding more text after the backslash adds to the pattern, as the backslash
+# serves to escape the ":" that is otherwise used to separate the modifiers.
+# The result is a single ":M" modifier with the pattern "x:Nzzz".
+.if ${BACKSLASH:Mx\:Nzzz} != ""
+.  error
+.endif
+
+# The pattern ends up as "x\:Nzzz".  Only the sequence "\:" is unescaped, all
+# others, including "\\", are left as-is.
+.if ${BACKSLASH:Mx\\:Nzzz} != ""
+.  error
+.endif
+
+# The pattern for the ":M" modifier ends up as "x\\\\\\\:Nzzz".  Only the
+# sequence "\:" is unescaped, all others, including "\\", are left as-is.
+.if ${BACKSLASH:Mx\\\\\\\\:Nzzz} != ""
+.  error
+.endif
+
+# The ":M" modifier is parsed differently than the other modifiers.  To
+# circumvent the peculiarities of that parser, the pattern can be passed via
+# an expression.  There, the usual escaping rules for modifiers apply.
+# expect+1: Unfinished backslash at the end in pattern "\" of modifier ":M"
+.if ${BACKSLASH:M${BACKSLASH}} != "\\"
+.  error
+.else
+.  error
+.endif
+
+# Trying to bypass the parser by using a direct expression doesn't work, as
+# the parser for the ":M" modifier does not parse the subexpression like in
+# all other places, but instead counts the braces and tries to decode the
+# escaping, which fails in this case.
+# expect+1: Unclosed expression, expecting "}" for modifier "M${:U\\\\}} != "\\""
+.if ${BACKSLASH:M${:U\\\\}} != "\\"
+.  error
+.else
+.  error
+.endif
+
+# Matching a backslash with the pattern matching characters works.
+.if ${BACKSLASH:M?} != "\\"
+.  error
+.endif
+.if ${BACKSLASH:M*} != "\\"
+.  error
+.endif
+.if ${BACKSLASH:M[Z-a]} != "\\"
+.  error
+.endif
+.if ${BACKSLASH:M[\\]} != "\\"
+.  error
+.endif
+
+# end https://gnats.netbsd.org/46139