From 7d6be9ffc4ef51af2d953245348ec6d8dbf5080a Mon Sep 17 00:00:00 2001
From: rillig <rillig@NetBSD.org>
Date: Sat, 22 Aug 2020 21:22:24 +0000
Subject: [PATCH] make(1): try to set the variable named "" using the command
 line

Before 2020-08-22, the command line argument '=cmline-plain' triggered
undefined behavior, just like the assignment '=assigned' in the Makefile.
---
 usr.bin/make/unit-tests/Makefile          |  4 +++-
 usr.bin/make/unit-tests/varname-empty.exp | 12 ++++++++++--
 usr.bin/make/unit-tests/varname-empty.mk  |  8 ++++----
 3 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/usr.bin/make/unit-tests/Makefile b/usr.bin/make/unit-tests/Makefile
index 19aef769d55e..275a77deef7b 100644
--- a/usr.bin/make/unit-tests/Makefile
+++ b/usr.bin/make/unit-tests/Makefile
@@ -1,4 +1,4 @@
-# $NetBSD: Makefile,v 1.111 2020/08/22 20:50:43 sjg Exp $
+# $NetBSD: Makefile,v 1.112 2020/08/22 21:22:24 rillig Exp $
 #
 # Unit tests for make(1)
 #
@@ -323,6 +323,7 @@ FLAGS.order=		-j1
 FLAGS.recursive=	-dL
 FLAGS.vardebug=		-k -dv FROM_CMDLINE=
 FLAGS.varmod-match-escape= -dv
+FLAGS.varname-empty=	-dv '$${:U}=cmdline-u' '=cmline-plain'
 
 # Some tests need extra post-processing.
 SED_CMDS.sh-dots+=	-e 's,^${.SHELL}: ,,'
@@ -336,6 +337,7 @@ SED_CMDS.varshell+=	-e '/command/s,No such.*,not found,'
 POSTPROC.counter=	${TOOL_SED} -n -e '/:RELEVANT = yes/,/:RELEVANT = no/p'
 POSTPROC.vardebug=	${TOOL_SED} -n -e '/:RELEVANT = yes/,/:RELEVANT = no/p'
 POSTPROC.varmod-match-escape= ${TOOL_SED} -n -e '/^Pattern/p'
+POSTPROC.varname-empty=	${TOOL_SED} -n -e '/^Var_Set/p' -e '/^out:/p'
 
 # Some tests reuse other tests, which makes them unnecessarily fragile.
 export-all.rawout: export.mk
diff --git a/usr.bin/make/unit-tests/varname-empty.exp b/usr.bin/make/unit-tests/varname-empty.exp
index 565cfb54fd61..77cb7c517e9d 100644
--- a/usr.bin/make/unit-tests/varname-empty.exp
+++ b/usr.bin/make/unit-tests/varname-empty.exp
@@ -1,3 +1,11 @@
-fallback
-1 2 3
+Var_Set("${:U}", "cmdline-u", ...) name expands to empty string - ignored
+Var_Set("", "cmline-plain", ...) name expands to empty string - ignored
+Var_Set("", "default", ...) name expands to empty string - ignored
+Var_Set("", "assigned", ...) name expands to empty string - ignored
+Var_Set("", "appended", ...) name expands to empty string - ignored
+Var_Set("", "", ...) name expands to empty string - ignored
+Var_Set("", "subst", ...) name expands to empty string - ignored
+Var_Set("", "shell-output", ...) name expands to empty string - ignored
+out: fallback
+out: 1 2 3
 exit status 0
diff --git a/usr.bin/make/unit-tests/varname-empty.mk b/usr.bin/make/unit-tests/varname-empty.mk
index 87de6ab09224..b4ce05c3017b 100644
--- a/usr.bin/make/unit-tests/varname-empty.mk
+++ b/usr.bin/make/unit-tests/varname-empty.mk
@@ -1,4 +1,4 @@
-# $NetBSD: varname-empty.mk,v 1.4 2020/08/22 21:12:29 rillig Exp $
+# $NetBSD: varname-empty.mk,v 1.5 2020/08/22 21:22:24 rillig Exp $
 #
 # Tests for the special variable with the empty name.
 #
@@ -12,7 +12,7 @@
 =	assigned	# undefined behavior until 2020-08-22
 +=	appended
 :=	subst
-!=	echo 'value'
+!=	echo 'shell-output'
 
 # The .for loop expands the expression ${i} to ${:U1}, ${:U2} and so on.
 # This only works if the variable with the empty name is guaranteed to
@@ -22,5 +22,5 @@ NUMBERS+=	${i}
 .endfor
 
 all:
-	@echo ${:Ufallback}
-	@echo ${NUMBERS}
+	@echo out: ${:Ufallback}
+	@echo out: ${NUMBERS}