diff --git a/src/cmd/ksh93/data/variables.c b/src/cmd/ksh93/data/variables.c
index d1e198d97bd3..2eb6cedb0d7c 100644
--- a/src/cmd/ksh93/data/variables.c
+++ b/src/cmd/ksh93/data/variables.c
@@ -105,9 +105,6 @@ const struct shtable2 shtab_variables[] =
 	".sh.pid",	NV_INTEGER|NV_NOFREE,		(char*)0,
 	".sh.tilde",	0,				(char*)0,
 	"SHLVL",	NV_INTEGER|NV_NOFREE|NV_EXPORT,	(char*)0,
-#if SHOPT_MULTIBYTE
-	"CSWIDTH",	0,				(char*)0,
-#endif /* SHOPT_MULTIBYTE */
 	"",	0,					(char*)0
 };
 
diff --git a/src/cmd/ksh93/tests/case.sh b/src/cmd/ksh93/tests/case.sh
index c6830499698f..8dda00dee070 100755
--- a/src/cmd/ksh93/tests/case.sh
+++ b/src/cmd/ksh93/tests/case.sh
@@ -96,8 +96,9 @@ got=$(eval 'case x in (foo);; (if);; esac' 2>&1) || err_exit "'(' + 'if' as nth
 # ======
 # Verify an invalid character class name is handled without a SIGSEGV or similar failure
 # https://github.com/att/ast/issues/1409
-got="$($SHELL -c 'case x in [x[:bogus:]]) echo x ;; esac')"
-[[ -z $got ]] || err_exit "invalid char class name (got $(printf %q "$got"))"
+got=$(set +x; { "$SHELL" -c 'case x in [x[:bogus:]]) echo x ;; esac'; } 2>&1)
+((!(e = $?))) && [[ -z $got ]] || err_exit 'use of invalid character class name' \
+	"(got status $e$( ((e>128)) && print -n /SIG && kill -l "$e"), $(printf %q "$got"))"
 
 # ======
 exit $((Errors<125?Errors:125))
diff --git a/src/cmd/ksh93/tests/coprocess.sh b/src/cmd/ksh93/tests/coprocess.sh
index 8b67ec8fb1e1..ad7bbf5aa2d0 100755
--- a/src/cmd/ksh93/tests/coprocess.sh
+++ b/src/cmd/ksh93/tests/coprocess.sh
@@ -23,8 +23,8 @@
 . "${SHTESTS_COMMON:-${0%/*}/_common}"
 
 if	[[ -d /cygdrive ]]
-then	err_exit 'Cygwin detected - coprocess tests disabled - enable at the risk of wedging your system'
-	exit $((Errors))
+then	warning 'Cygwin detected - coprocess tests disabled - enable at the risk of wedging your system'
+	exit 0
 fi
 
 bintrue=$(whence -p true)
diff --git a/src/cmd/ksh93/tests/grep.sh b/src/cmd/ksh93/tests/grep.sh
index 200e87ffd5ad..45512d3b2b13 100755
--- a/src/cmd/ksh93/tests/grep.sh
+++ b/src/cmd/ksh93/tests/grep.sh
@@ -85,11 +85,12 @@ and some lines contain bar only.
 However, many lines contain both foo and also bar.
 A line containing foobar should also be counted.
 There should be six lines with foo and bar.
-There are only two line with out foo but with bar.
+There are only two lines without foo but with bar.
 !
 
-if	(( $(grep -c 'foo*bar' $tmp/grep ) != 6))
-then	err_exit
+got=$(grep -c 'foo*bar' $tmp/grep 2>&1)
+if	[[ $got != 6 ]]
+then	err_exit "shell version of grep fails (expected 6, got $(printf %q "$got"))"
 fi
 
 exit $((Errors<125?Errors:125))
diff --git a/src/cmd/ksh93/tests/subshell.sh b/src/cmd/ksh93/tests/subshell.sh
index a00440ec6006..1c2d64e956cc 100755
--- a/src/cmd/ksh93/tests/subshell.sh
+++ b/src/cmd/ksh93/tests/subshell.sh
@@ -65,16 +65,22 @@ z.bar[1]=(x=12 y=5)
 eval val="$z"
 (
 	z.foo[three]=good
-	[[ ${z.foo[three]} == good ]] || err_exit 'associative array assignment in subshell not working'
-)
+	[[ ${z.foo[three]} == good ]]
+) || err_exit 'associative array assignment in subshell not working'
 [[ $z == "$val" ]] || err_exit 'compound variable changes after associative array assignment'
 eval val="$z"
 (
 	z.foo[two]=ok
-	[[ ${z.foo[two]} == ok ]] || err_exit 'associative array assignment to compound variable in subshell not working'
+	[[ ${z.foo[two]} == ok ]] || exit 101
 	z.bar[1]=yes
-	[[ ${z.bar[1]} == yes ]] || err_exit 'indexed array assignment to compound variable in subshell not working'
+	[[ ${z.bar[1]} == yes ]] || exit 102
 )
+case $? in
+0)	;;
+101)	err_exit 'associative array assignment to compound variable in subshell not working' ;;
+102)	err_exit 'indexed array assignment to compound variable in subshell not working' ;;
+*)	err_exit 'assignment to compound variable in subshell fails' ;;
+esac
 [[ $z == "$val" ]] || err_exit 'compound variable changes after associative array assignment'
 
 x=(
@@ -84,10 +90,16 @@ x=(
 eval val="$x"
 (
 	unset x.foo
-	[[ ${x.foo.qqq} ]] && err_exit 'x.foo.qqq should be unset'
+	[[ ${x.foo.qqq} ]] && exit 101
 	x.foo=good
-	[[ ${x.foo} == good ]] || err_exit 'x.foo should be good'
+	[[ ${x.foo} == good ]] || exit 102
 )
+case $? in
+0)	;;
+101)	err_exit 'x.foo.qqq should be unset' ;;
+102)	err_exit 'x.foo should be good' ;;
+*)	err_exit "x.foo fails" ;;
+esac
 [[ $x == "$val" ]] || err_exit 'compound variable changes after unset leaves'
 unset l
 (
diff --git a/src/cmd/ksh93/tests/variables.sh b/src/cmd/ksh93/tests/variables.sh
index 40b0a1b9e69b..62c25606741b 100755
--- a/src/cmd/ksh93/tests/variables.sh
+++ b/src/cmd/ksh93/tests/variables.sh
@@ -619,8 +619,10 @@ chmod +x $tmp/script
     [[ $(fun .sh.subshell) == 2 ]]  || err_exit ".sh.subshell not working for functions in subshells"
     (( .sh.subshell == 1 )) || err_exit ".sh.subshell not working in a subshell"
 )
-TIMEFORMAT='this is a test'
-[[ $(set +x; { { time :;} 2>&1;}) == "$TIMEFORMAT" ]] || err_exit 'TIMEFORMAT not working'
+(
+	TIMEFORMAT='this is a test'
+	[[ $(set +x; { { time :;} 2>&1;}) == "$TIMEFORMAT" ]]
+) || err_exit 'TIMEFORMAT not working'
 alias _test_alias=true
 : ${.sh.version}
 [[ $(alias _test_alias) == *.sh.* ]] && err_exit '.sh. prefixed to alias name'
@@ -965,75 +967,25 @@ actual=$(env SHLVL="2#11+x[\$(env echo Exploited vuln CVE-2019-14868 >&2)0]" "$S
 # ======
 # Check unset, attribute and cleanup/restore behavior of special variables.
 
-# Keep the list in sync (minus ".sh") with shtab_variables[] in src/cmd/ksh93/data/variables.c
-set -- \
-	"PATH" \
-	"PS1" \
-	"PS2" \
-	"IFS" \
-	"PWD" \
-	"HOME" \
-	"MAIL" \
-	"REPLY" \
-	"SHELL" \
-	"EDITOR" \
-	"MAILCHECK" \
-	"RANDOM" \
-	"ENV" \
-	"HISTFILE" \
-	"HISTSIZE" \
-	"HISTEDIT" \
-	"HISTCMD" \
-	"FCEDIT" \
-	"CDPATH" \
-	"MAILPATH" \
-	"PS3" \
-	"OLDPWD" \
-	"VISUAL" \
-	"COLUMNS" \
-	"LINES" \
-	"PPID" \
-	"_" \
-	"TMOUT" \
-	"SECONDS" \
-	"LINENO" \
-	"OPTARG" \
-	"OPTIND" \
-	"PS4" \
-	"FPATH" \
-	"LANG" \
-	"LC_ALL" \
-	"LC_COLLATE" \
-	"LC_CTYPE" \
-	"LC_MESSAGES" \
-	"LC_NUMERIC" \
-	"LC_TIME" \
-	"FIGNORE" \
-	"KSH_VERSION" \
-	"JOBMAX" \
-	".sh.edchar" \
-	".sh.edcol" \
-	".sh.edtext" \
-	".sh.edmode" \
-	".sh.name" \
-	".sh.subscript" \
-	".sh.value" \
-	".sh.version" \
-	".sh.dollar" \
-	".sh.match" \
-	".sh.command" \
-	".sh.file" \
-	".sh.fun" \
-	".sh.lineno" \
-	".sh.subshell" \
-	".sh.level" \
-	".sh.stats" \
-	".sh.math" \
-	".sh.pool" \
-	".sh.pid" \
-	".sh.tilde" \
-	"SHLVL" \
-	"CSWIDTH"
+# ... to avoid forgetting to keep this script synched with shtab_variables[], read from the source
+set -- $(
+	srcdir=${SHTESTS_COMMON%/tests/*}
+	redirect < $srcdir/data/variables.c || exit
+	# skip lines until finding shtab_variables struct
+	while	read -r line || exit
+	do	[[ $line == *" shtab_variables[] =" ]] && break
+	done
+	read -r line
+	[[ $line == '{' ]] || exit
+	# read variable names until '};'
+	IFS=\"
+	while	read -r first varname junk
+	do	[[ $first == '};' ]] && exit
+		[[ -z $junk ]] && continue
+		[[ -n $varname && $varname != '.sh' ]] && print -r -- "$varname"
+	done
+)
+(($# >= 66)) || err_exit "could not read shtab_variables[]; adjust test script ($# items read)"
 
 # ... unset
 $SHELL -c '