From de7eb8525501c47724fe5643bdbdc2647680aa69 Mon Sep 17 00:00:00 2001
From: Martijn Dekker <martijn@inlv.org>
Date: Tue, 19 Jan 2021 18:23:14 +0000
Subject: [PATCH] sh_subsavefd(): avoid a negative shift operand

This change is backported from the abandoned ksh 93v- beta.

src/cmd/ksh93/sh/subshell.c: sh_subsavefd():
- Do not subtract 1 from fd, as this would cause a negative shift
  operand for stdin (fd==0).
---
 src/cmd/ksh93/sh/subshell.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/cmd/ksh93/sh/subshell.c b/src/cmd/ksh93/sh/subshell.c
index e8d785361..283b30f8d 100644
--- a/src/cmd/ksh93/sh/subshell.c
+++ b/src/cmd/ksh93/sh/subshell.c
@@ -90,7 +90,7 @@ static struct subshell
 	char		jobcontrol;
 	char		monitor;
 	unsigned char	fdstatus;
-	int		fdsaved; /* bit make for saved files */
+	int		fdsaved; /* bit mask for saved file descriptors */
 	int		sig;	/* signal for $$ */
 	pid_t		bckpid;
 	pid_t		cpid;
@@ -457,8 +457,8 @@ int sh_subsavefd(register int fd)
 	register int old=0;
 	if(sp)
 	{
-		old = !(sp->fdsaved&(1<<(fd-1)));
-		sp->fdsaved |= (1<<(fd-1));
+		old = !(sp->fdsaved&(1<<fd));
+		sp->fdsaved |= (1<<fd);
 	}
 	return(old);
 }