From 417883dfdd4a39bd882285e74f6fbe9b1aea47a3 Mon Sep 17 00:00:00 2001
From: Martijn Dekker <martijn@inlv.org>
Date: Sat, 5 Sep 2020 16:48:17 +0200
Subject: [PATCH] Revert "Fix subshell leak for 4 special variables (re:
 bd3e2a80)"

This reverts commit b3d37b00b0d46d434c90b4e5a3673fc3f5d5a197.
While ksh's own regression test suite passed just fine, when
running the modernish[*] regression tests uite, ksh either froze
hard (needing SIGKILL) or threw a spurious syntax error.
Cause unknown, but I'm certainly reverting until I find out.

This reintroduces a subshell leak for four special variables.

[*] https://github.com/modernish/modernish
---
 src/cmd/ksh93/bltins/typeset.c   |  6 +++---
 src/cmd/ksh93/sh/subshell.c      | 11 +++++++++--
 src/cmd/ksh93/tests/variables.sh | 14 --------------
 3 files changed, 12 insertions(+), 19 deletions(-)

diff --git a/src/cmd/ksh93/bltins/typeset.c b/src/cmd/ksh93/bltins/typeset.c
index a1591883e..52b9c899e 100644
--- a/src/cmd/ksh93/bltins/typeset.c
+++ b/src/cmd/ksh93/bltins/typeset.c
@@ -688,7 +688,7 @@ static int     setall(char **argv,register int flag,Dt_t *troot,struct tdata *tp
 					 * 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,1);
+					np=sh_assignok(np,2);
 				}
 				else
 					np=sh_assignok(np,0);
@@ -800,7 +800,7 @@ static int     setall(char **argv,register int flag,Dt_t *troot,struct tdata *tp
 			if (tp->aflag && (tp->argnum>0 || (curflag!=newflag)))
 			{
 				if(shp->subshell)
-					sh_assignok(np,1);
+					sh_assignok(np,3);
 				if(troot!=shp->var_tree)
 					nv_setattr(np,newflag&~NV_ASSIGN);
 				else
@@ -1285,7 +1285,7 @@ static int unall(int argc, char **argv, register Dt_t *troot, Shell_t* shp)
 						 * 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,1);
+						np=sh_assignok(np,2);
 					}
 					else
 						np=sh_assignok(np,0);
diff --git a/src/cmd/ksh93/sh/subshell.c b/src/cmd/ksh93/sh/subshell.c
index 5ecbc94ce..87c7d65b2 100644
--- a/src/cmd/ksh93/sh/subshell.c
+++ b/src/cmd/ksh93/sh/subshell.c
@@ -233,6 +233,10 @@ int nv_subsaved(register Namval_t *np)
  *
  * add == 0:    Move the node pointer from the parent shell to the current virtual subshell.
  * add == 1:    Create a copy of the node pointer in the current virtual subshell.
+ * add == 2:    This will create a copy of the node pointer like 1, but it will disable the
+ *              optimization for ${.sh.level}.
+ * add == 3:    This is like 1, but it will never skip the following variables:
+ *              ${.sh.level}, $_, ${.sh.subscript} and ${.sh.name}.
  */
 Namval_t *sh_assignok(register Namval_t *np,int add)
 {
@@ -244,8 +248,11 @@ Namval_t *sh_assignok(register Namval_t *np,int add)
 	Namval_t		*mpnext;
 	Namarr_t		*ap;
 	unsigned int		save;
-	/* don't save if told not to (see nv_restore()) or if we're in a ${ subshare; } */
-	if(!sp->shpwd || shp->subshare)
+	/* don't bother to save if in a ${ subshare; } */
+	if(sp->subshare)
+		return(np);
+	/* don't bother with this */
+	if(!sp->shpwd || (add != 3 && ((add != 2 && np==SH_LEVELNOD) || np==L_ARGNOD || np==SH_SUBSCRNOD || np==SH_NAMENOD)))
 		return(np);
 	if((ap=nv_arrayptr(np)) && (mp=nv_opensub(np)))
 	{
diff --git a/src/cmd/ksh93/tests/variables.sh b/src/cmd/ksh93/tests/variables.sh
index f122ed5d4..0ffe75dd4 100755
--- a/src/cmd/ksh93/tests/variables.sh
+++ b/src/cmd/ksh93/tests/variables.sh
@@ -1011,20 +1011,6 @@ $SHELL -c '
 e=$?
 ((e == 1)) || err_exit "Failure in making one or more special variables readonly in a subshell (exit status $e)"
 
-# ... subshell leak test
-$SHELL -c '
-	errors=0
-	for var
-	do	if	eval "($var=bug); [[ \${$var} == bug ]]" 2>/dev/null
-		then	echo "	$0: special variable $var leaks out of subshell" >&2
-			let errors++
-		fi
-	done
-	exit $((errors + 1))
-' subshell_leak_test "$@"
-e=$?
-((e == 1)) || err_exit "One or more special variables leak out of a subshell (exit status $e)"
-
 # ======
 # ${.sh.pid} should be the forked subshell's PID
 (