1 files changed, 48 insertions, 6 deletions

diff --git a/unit-tests/deptgt-makeflags.mk b/unit-tests/deptgt-makeflags.mk
index 70a9cd0b590b..0a0f410e14c4 100644
--- a/unit-tests/deptgt-makeflags.mk
+++ b/unit-tests/deptgt-makeflags.mk
@@ -1,30 +1,35 @@
-# $NetBSD: deptgt-makeflags.mk,v 1.4 2020/10/23 14:48:49 rillig Exp $
+# $NetBSD: deptgt-makeflags.mk,v 1.6 2020/11/15 20:20:58 rillig Exp $
 #
 # Tests for the special target .MAKEFLAGS in dependency declarations,
 # which adds command line options later, at parse time.
+#
+# In these unit tests, it is often used to temporarily toggle the debug log
+# during parsing.
 
 # The -D option sets a variable in the "Global" scope and thus can be
 # undefined later.
 .MAKEFLAGS: -D VAR
-
 .if ${VAR} != 1
 .  error
 .endif
 
+# Variables that are set via the -D command line option are normal global
+# variables and can thus be undefined later.
 .undef VAR
-
 .if defined(VAR)
 .  error
 .endif
 
+# The -D command line option can define a variable again, after it has been
+# undefined.
 .MAKEFLAGS: -D VAR
-
 .if ${VAR} != 1
 .  error
 .endif
 
+# The "dependency" for .MAKEFLAGS is split into words, interpreting the usual
+# quotes and escape sequences from the backslash.
 .MAKEFLAGS: VAR="value"' with'\ spaces
-
 .if ${VAR} != "value with spaces"
 .  error
 .endif
@@ -32,7 +37,6 @@
 # Variables set on the command line as VAR=value are placed in the
 # "Command" scope and thus cannot be undefined.
 .undef VAR
-
 .if ${VAR} != "value with spaces"
 .  error
 .endif
@@ -47,5 +51,43 @@
 .endif
 .MAKEFLAGS: -d0
 
+# An empty command line is skipped.
+.MAKEFLAGS: # none
+
+# Escape sequences like \n are interpreted.
+# The following line looks as if it assigned a newline to nl, but it doesn't.
+# Instead, the \n ends up as a line that is then interpreted as a variable
+# assignment.  At that point, the line is simply "nl=\n", and the \n is
+# skipped since it is whitespace (see Parse_IsVar).
+.MAKEFLAGS: nl="\n"
+.if ${nl} != ""
+.  error
+.endif
+
+# Next try at defining another newline variable.  Since whitespace around the
+# variable value is trimmed, two empty variable expressions surround the
+# literal newline now.  This prevents the newline from being skipped during
+# parsing.  The ':=' assignment operator expands the empty variable
+# expressions, leaving only the newline as the variable value.
+#
+# This is one of the very few ways (maybe even the only one) to inject literal
+# newlines into a line that is being parsed.  This may confuse the parser.
+# For example, in cond.c the parser only expects horizontal whitespace (' '
+# and '\t'), but no newlines.
+#.MAKEFLAGS: -dcpv
+.MAKEFLAGS: nl:="$${:U}\n$${:U}"
+.if ${nl} != ${.newline}
+.  error
+.endif
+#.MAKEFLAGS: -d0
+
+# Unbalanced quotes produce an error message.  If they occur anywhere in the
+# command line, the whole command line is skipped.
+.MAKEFLAGS: VAR=previous
+.MAKEFLAGS: VAR=initial UNBALANCED='
+.if ${VAR} != "previous"
+.  error
+.endif
+
 all:
 	@:;