From 119fb2a288a48b566f5b2c195edfdb980f876d76 Mon Sep 17 00:00:00 2001
From: Xin LI <delphij@FreeBSD.org>
Date: Tue, 1 Jul 2025 22:09:29 -0700
Subject: [PATCH] sh(1): Do not interpret chdir to "" as equivalent to chdir
 with no argument

A script that does the following:

    cd "${dir}" || exit 1

would incorrectly remain in the current directory when `${dir}` is
an empty string under the current implementation. This behavior,
while historical, is potentially dangerous, as it is likely not
what the script author intended.

Change the command to treat an empty string as an error and emit a
diagnostic message to standard error, as required by
IEEE Std 1003.1-2024.

PR:		standards/287440
Test Plan:	kyua test bin/sh
Relnotes:	yes
Differential Revision: https://reviews.freebsd.org/D50974
---
 bin/sh/cd.c                         | 2 --
 bin/sh/tests/builtins/Makefile      | 1 +
 bin/sh/tests/builtins/cd12.0        | 3 +++
 bin/sh/tests/builtins/cd12.0.stderr | 1 +
 4 files changed, 5 insertions(+), 2 deletions(-)
 create mode 100644 bin/sh/tests/builtins/cd12.0
 create mode 100644 bin/sh/tests/builtins/cd12.0.stderr

diff --git a/bin/sh/cd.c b/bin/sh/cd.c
index b908c4320c0..6f97bff3c9f 100644
--- a/bin/sh/cd.c
+++ b/bin/sh/cd.c
@@ -99,8 +99,6 @@ cdcmd(int argc __unused, char **argv __unused)
 
 	if ((dest = *argptr) == NULL && (dest = bltinlookup("HOME", 1)) == NULL)
 		error("HOME not set");
-	if (*dest == '\0')
-		dest = ".";
 	if (dest[0] == '-' && dest[1] == '\0') {
 		dest = bltinlookup("OLDPWD", 1);
 		if (dest == NULL)
diff --git a/bin/sh/tests/builtins/Makefile b/bin/sh/tests/builtins/Makefile
index ac959b17c63..7fdecb23c81 100644
--- a/bin/sh/tests/builtins/Makefile
+++ b/bin/sh/tests/builtins/Makefile
@@ -52,6 +52,7 @@ ${PACKAGE}FILES+=		cd8.0
 ${PACKAGE}FILES+=		cd9.0 cd9.0.stdout
 ${PACKAGE}FILES+=		cd10.0
 ${PACKAGE}FILES+=		cd11.0
+${PACKAGE}FILES+=		cd12.0 cd12.0.stderr
 ${PACKAGE}FILES+=		command1.0
 ${PACKAGE}FILES+=		command2.0
 ${PACKAGE}FILES+=		command3.0
diff --git a/bin/sh/tests/builtins/cd12.0 b/bin/sh/tests/builtins/cd12.0
new file mode 100644
index 00000000000..34bc053afd1
--- /dev/null
+++ b/bin/sh/tests/builtins/cd12.0
@@ -0,0 +1,3 @@
+(cd /bin) || exit 1
+cd "" && exit 1
+exit 0
diff --git a/bin/sh/tests/builtins/cd12.0.stderr b/bin/sh/tests/builtins/cd12.0.stderr
new file mode 100644
index 00000000000..cce88588b90
--- /dev/null
+++ b/bin/sh/tests/builtins/cd12.0.stderr
@@ -0,0 +1 @@
+cd: : No such file or directory