From 82bfcc37e2677394ccb075cdb64e5873ec5e906d Mon Sep 17 00:00:00 2001
From: Mike Yuan <me@yhndnzj.com>
Date: Wed, 25 Mar 2026 16:45:27 +0100
Subject: [PATCH 1/4] cleanup-util: include assert-fundamental.h instead of
 -util

The split was initially done to reduce transitive includes,
and for assert() only the former is needed.
---
 src/basic/cleanup-util.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/basic/cleanup-util.h b/src/basic/cleanup-util.h
index 068696d977..041c37530a 100644
--- a/src/basic/cleanup-util.h
+++ b/src/basic/cleanup-util.h
@@ -1,7 +1,7 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 #pragma once
 
-#include "assert-util.h"
+#include "assert-fundamental.h"
 #include "cleanup-fundamental.h" /* IWYU pragma: export */
 
 typedef void (*free_func_t)(void *p);

From 1060f82611be352bf77ec1eb82ec8e536849174a Mon Sep 17 00:00:00 2001
From: Mike Yuan <me@yhndnzj.com>
Date: Wed, 25 Mar 2026 15:39:26 +0100
Subject: [PATCH 2/4] creds: use parse_tristate_argument_with_auto() where
 appropriate

---
 src/creds/creds.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/src/creds/creds.c b/src/creds/creds.c
index 5f60f781f6..9e1b2cfbcc 100644
--- a/src/creds/creds.c
+++ b/src/creds/creds.c
@@ -940,15 +940,9 @@ static int parse_argv(int argc, char *argv[]) {
                         break;
 
                 case ARG_NEWLINE:
-                        if (isempty(optarg) || streq(optarg, "auto"))
-                                arg_newline = -1;
-                        else {
-                                r = parse_boolean_argument("--newline=", optarg, NULL);
-                                if (r < 0)
-                                        return r;
-
-                                arg_newline = r;
-                        }
+                        r = parse_tristate_argument_with_auto("--newline=", optarg, &arg_newline);
+                        if (r < 0)
+                                return r;
                         break;
 
                 case 'p':

From 64d1c102ad3af9ce5f640b2fbffb8113697fd0e3 Mon Sep 17 00:00:00 2001
From: Mike Yuan <me@yhndnzj.com>
Date: Wed, 25 Mar 2026 16:00:14 +0100
Subject: [PATCH 3/4] creds: if newline is explicitly requested, skip tty check

Before this commit, the > 0 state of arg_newline tristate is
simply ignored.

Yes, this is a minor compat break, but I'd argue the previous
behavior was not useful as "yes" is treated the same as "auto".
An issue also reported that it was quite surprising.

Fixes #41348
---
 src/creds/creds.c           | 12 ++++++------
 test/units/TEST-54-CREDS.sh |  5 ++---
 2 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/src/creds/creds.c b/src/creds/creds.c
index 9e1b2cfbcc..3103686a9f 100644
--- a/src/creds/creds.c
+++ b/src/creds/creds.c
@@ -398,8 +398,6 @@ static int transcode(
 }
 
 static int print_newline(FILE *f, const char *data, size_t l) {
-        int fd;
-
         assert(f);
         assert(data || l == 0);
 
@@ -411,10 +409,12 @@ static int print_newline(FILE *f, const char *data, size_t l) {
         if (l > 0 && data[l-1] == '\n')
                 return 0;
 
-        /* Don't bother unless this is a tty */
-        fd = fileno(f);
-        if (fd >= 0 && !isatty_safe(fd))
-                return 0;
+        /* If not explicitly requested, don't bother if the output is not a tty */
+        if (arg_newline < 0) {
+                int fd = fileno(f);
+                if (fd >= 0 && !isatty_safe(fd))
+                        return 0;
+        }
 
         if (fputc('\n', f) != '\n')
                 return log_error_errno(errno, "Failed to write trailing newline: %m");
diff --git a/test/units/TEST-54-CREDS.sh b/test/units/TEST-54-CREDS.sh
index 0eaf8a2dfb..523046ec76 100755
--- a/test/units/TEST-54-CREDS.sh
+++ b/test/units/TEST-54-CREDS.sh
@@ -114,10 +114,9 @@ run_with_cred_compare "mycred:" "" cat mycred
 run_with_cred_compare "mycred:\n" "\n" cat mycred
 run_with_cred_compare "mycred:foo" "foo" cat mycred
 run_with_cred_compare "mycred:foo" "foofoofoo" cat mycred mycred mycred
-# Note: --newline= does nothing when stdout is not a tty, which is the case here
-run_with_cred_compare "mycred:foo" "foo" --newline=yes cat mycred
-run_with_cred_compare "mycred:foo" "foo" --newline=no cat mycred
 run_with_cred_compare "mycred:foo" "foo" --newline=auto cat mycred
+run_with_cred_compare "mycred:foo" "foo" --newline=no cat mycred
+run_with_cred_compare "mycred:foo" "foo\n" --newline=yes cat mycred
 run_with_cred_compare "mycred:foo" "foo" --transcode=no cat mycred
 run_with_cred_compare "mycred:foo" "foo" --transcode=0 cat mycred
 run_with_cred_compare "mycred:foo" "foo" --transcode=false cat mycred

From 734af2908a803c17ad587da7db334fc225f18dde Mon Sep 17 00:00:00 2001
From: Mike Yuan <me@yhndnzj.com>
Date: Wed, 25 Mar 2026 16:03:07 +0100
Subject: [PATCH 4/4] creds: minor tweak for fputc() error handling

Let's do not assume errno is set for return values other than
EOF, following what we do in fileio.c.
---
 src/creds/creds.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/creds/creds.c b/src/creds/creds.c
index 3103686a9f..3b1cc8e86b 100644
--- a/src/creds/creds.c
+++ b/src/creds/creds.c
@@ -416,7 +416,7 @@ static int print_newline(FILE *f, const char *data, size_t l) {
                         return 0;
         }
 
-        if (fputc('\n', f) != '\n')
+        if (fputc('\n', f) == EOF)
                 return log_error_errno(errno, "Failed to write trailing newline: %m");
 
         return 1;