Fix typeset attributes -a, -A, -l, -u leaking out of subshells

If an array or upper/lowercase variable was declared with a null
initial value within a virtual/non-forked subshell, like:
	( typeset -a foo; ... )
	( typeset -A foo; ... )
	( typeset -l foo; ... )
	( typeset -u foo; ... )
then the type declaration leaked out of the subshell into the
parent shell environment, though without any values that may
subsequently have been assigned.

src/cmd/ksh93/bltins/typeset.c: setall():
- When deciding whether to create a virtual subshell scope for a
  variable, use sh_assignok(), which was actually designed for the
  purpose, instead of _nv_unset(). This allows getting rid of a
  tangled mess of special-casing that never worked quite right.

src/cmd/ksh93/tests/arrays.sh:
- Add regression tests checking that array declarations don't leak
  out of virtual subshells.

src/cmd/ksh93/tests/attributes.sh:
- Add regression tests for combining the 'export' and 'readonly'
  attributes with every other possible typeset attribute on unset
  variables. This also includes a subshell leak test for each one.

Fixes: https://github.com/ksh93/ksh/issues/88

NEWS

@@ -15,6 +15,9 @@ Any uppercase BUG_* names are modernish shell bug IDs.
   an unrecognized option. 'sleep -: 1' will now show a usage message and
   exit instead of sleep for one second.
 
+- Fixed a bug that caused the 'typeset' variable attributes -a, -A, -l, and
+  -u to leak out of a subshell if they were set without assigning a value.
+
 2020-07-23:
 
 - Fixed an infinite loop that could occur when ksh is the system's /bin/sh.

src/cmd/ksh93/bltins/typeset.c

@@ -691,13 +691,22 @@ static int     setall(char **argv,register int flag,Dt_t *troot,struct tdata *tp
 				if(!comvar && !iarray)
 					continue;
 			}
-			if(!nv_isarray(np) && !strchr(name,'=') && !(shp->envlist  && nv_onlist(shp->envlist,name)))
+
+			/* Create local scope for virtual subshell */
+			if(shp->subshell)
 			{
-				if(comvar || (shp->last_root==shp->var_tree && (tp->tp || (!shp->st.real_fun && (nvflags&NV_STATIC)) || (!(flag&(NV_EXPORT|NV_RDONLY)) && nv_isattr(np,(NV_EXPORT|NV_IMPORT))==(NV_EXPORT|NV_IMPORT)))))
-{
-					_nv_unset(np,0);
-}
+				if(!nv_isattr(np,NV_NODISC|NV_ARRAY) && !nv_isvtree(np))
+				{
+					/*
+					 * Variables with internal trap/discipline functions (LC_*, LINENO, etc.) need to be
+					 * cloned, as moving them will remove the discipline function.
+					 */
+					np=sh_assignok(np,2);
+				}
+				else
+					np=sh_assignok(np,0);
 			}
+
 			if(troot==shp->var_tree)
 			{
 				if(iarray)

src/cmd/ksh93/tests/arrays.sh

@@ -180,6 +180,12 @@ then    err_exit 'arithmetic expressions in typeset not working'
 fi
 unset foo
 typeset foo=bar
+typeset -a foo
+if	[[ ${foo[0]} != bar ]]
+then	err_exit 'initial value not preserved when typecast to indexed array'
+fi
+unset foo
+typeset foo=bar
 typeset -A foo
 if	[[ ${foo[0]} != bar ]]
 then	err_exit 'initial value not preserved when typecast to associative'
@@ -674,5 +680,32 @@ actual=$("$SHELL" -c 'A[0]="'\''" B[0]=aa C[0]=aa; typeset -a') \
 [[ $actual == "$expect" ]] || err_exit 'Incorrect output when listing indexed array' \
 	"(expected $(printf %q "$expect"), got $(printf %q "$actual"))"
 
+# ======
+# Arrays in virtual/non-forked subshells
+
+unset foo
+(typeset -a foo)
+[[ -n ${ typeset -p foo; } ]] && err_exit 'Null indexed array leaks out of subshell'
+
+unset foo
+(typeset -a foo=(1 2 3))
+[[ -n ${ typeset -p foo; } ]] && err_exit 'Indexed array with init value leaks out of subshell'
+
+unset foo
+(typeset -a foo; foo=(1 2 3))
+[[ -n ${ typeset -p foo; } ]] && err_exit 'Indexed array leaks out of subshell'
+
+unset foo
+(typeset -A foo)
+[[ -n ${ typeset -p foo; } ]] && err_exit 'Null associative array leaks out of subshell'
+
+unset foo
+(typeset -A foo=([bar]=baz [lorem]=ipsum))
+[[ -n ${ typeset -p foo; } ]] && err_exit 'Associative array with init value leaks out of subshell'
+
+unset foo
+(typeset -A foo; foo=([bar]=baz [lorem]=ipsum))
+[[ -n ${ typeset -p foo; } ]] && err_exit 'Associative array leaks out of subshell'
+
 # ======
 exit $((Errors<125?Errors:125))

src/cmd/ksh93/tests/attributes.sh

@@ -468,4 +468,53 @@ typeset -Z2 foo=3
 export foo
 [[ $(typeset -p foo) == 'typeset -x -Z 2 -R 2 foo=03' ]] || err_exit '-Z2  not working after export'
 
+# ======
+# unset exported readonly variables, combined with all other possible attributes
+typeset -A expect=(
+	[a]='typeset -x -r -a foo'
+	[b]='typeset -x -r -b foo'
+	[i]='typeset -x -r -i foo'
+	[i37]='typeset -x -r -i 37 foo'
+	[l]='typeset -x -r -l foo'
+	[n]='typeset -n -r foo'
+	[s]='typeset -x -r -s -i 0 foo=0'
+	[u]='typeset -x -r -u foo'
+	[A]='typeset -x -r -A foo=()'
+	[C]='typeset -x -r foo=()'
+	[E]='typeset -x -r -E foo'
+	[E12]='typeset -x -r -E 12 foo'
+	[F]='typeset -x -r -F foo'
+	[F12]='typeset -x -r -F 12 foo'
+	[H]='typeset -x -r -H foo'
+	[L]='typeset -x -r -L 0 foo'
+#	[L17]='typeset -x -r -L 17 foo'		# TODO: outputs '-L 0'
+	[Mtolower]='typeset -x -r -l foo'
+	[Mtoupper]='typeset -x -r -u foo'
+	[R]='typeset -x -r -R 0 foo'
+#	[R17]='typeset -x -r -R 17 foo'		# TODO: outputs '-L 0'
+	[X]='typeset -x -r -X 32 foo'
+	[X17]='typeset -x -r -X 17 foo'
+	[S]='typeset -x -r foo'
+	[T]='typeset -x -r foo'
+	[Z]='typeset -x -r -Z 0 -R 0 foo'
+#	[Z13]='typeset -x -r -Z 13 -R 13 foo'	# TODO: outputs 'typeset -x -r -Z 0 -R 0 foo'
+)
+for flag in a b i i37 l n s u A C E E12 F F12 H L Mtolower Mtoupper R X X17 S T Z
+do	unset foo
+	actual=$(
+		redirect 2>&1
+		export foo
+		(typeset "-$flag" foo; readonly foo; typeset -p foo)
+		typeset +x foo  # unexport
+		leak=${ typeset -p foo; }
+		[[ -n $leak ]] && print "SUBSHELL LEAK: $leak"
+	)
+	if	[[ $actual != "${expect[$flag]}" ]]
+	then	err_exit "unset exported readonly with -$flag:" \
+			"expected $(printf %q "${expect[$flag]}"), got $(printf %q "$actual")"
+	fi
+done
+unset expect
+
+# ======
 exit $((Errors<125?Errors:125))