[PATCH v2 00/13] selftests: Fix build warnings and errors

[PATCH v2 00/13] selftests: Fix build warnings and errors

[Guenter Roeck]

This series fixes build warnings and errors observed when trying to build
selftests.

v2: Emphasize that the patch series fixes build warnings and errors
    which are seen even if -Werror is not provided.
    Fix usage of cc-option.
    For "ignoring return value" warnings, use perror() to display an error
    message if the affected function returns an error.

----------------------------------------------------------------
Guenter Roeck (13):
      clone3: clone3_cap_checkpoint_restore: Fix build warnings
      selftests: ntsync: Fix build warnings
      selftests/filesystems: fclog: Fix build warnings and errors
      selftests/filesystems: file_stressor: Fix build warning
      selftests/filesystems: anon_inode_test: Fix build warning
      selftest: af_unix: Support compilers without flex-array-member-not-at-end support
      selftest/futex: Comment out test_futex_mpol
      selftests: net: netlink-dumps: Avoid uninitialized variable warning
      selftests/seccomp: Fix build warning
      selftests: net: Fix build warnings
      selftests/fs/mount-notify: Fix build warning
      selftests/fs/mount-notify-ns: Fix build warning
      selftests: net: tfo: Fix build warning

 tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c     | 4 ----
 tools/testing/selftests/drivers/ntsync/ntsync.c                    | 4 ++--
 tools/testing/selftests/filesystems/anon_inode_test.c              | 1 +
 tools/testing/selftests/filesystems/fclog.c                        | 1 +
 tools/testing/selftests/filesystems/file_stressor.c                | 2 --
 .../testing/selftests/filesystems/mount-notify/mount-notify_test.c | 3 ++-
 .../selftests/filesystems/mount-notify/mount-notify_test_ns.c      | 3 ++-
 tools/testing/selftests/futex/functional/futex_numa_mpol.c         | 2 ++
 tools/testing/selftests/net/af_unix/Makefile                       | 7 ++++++-
 tools/testing/selftests/net/lib/ksft.h                             | 6 ++++--
 tools/testing/selftests/net/netlink-dumps.c                        | 2 +-
 tools/testing/selftests/net/tfo.c                                  | 3 ++-
 tools/testing/selftests/seccomp/seccomp_bpf.c                      | 3 ++-
 13 files changed, 25 insertions(+), 16 deletions(-)

[PATCH v2 01/13] clone3: clone3_cap_checkpoint_restore: Fix build warnings

[Guenter Roeck]

Fix:

clone3_cap_checkpoint_restore.c:56:7: warning: unused variable 'ret'
   56 |                 int ret;
      |                     ^~~
clone3_cap_checkpoint_restore.c:57:8: warning: unused variable 'tmp'
   57 |                 char tmp = 0;
      |                      ^~~
clone3_cap_checkpoint_restore.c:138:6: warning: unused variable 'ret'
  138 |         int ret = 0;

by removing the unused variables.

Fixes: 1d27a0be16d6 ("selftests: add clone3() CAP_CHECKPOINT_RESTORE test")
Cc: Adrian Reber <areber@redhat.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2: Update subject and description to reflect that the patch fixes build
    warnings 

 .../testing/selftests/clone3/clone3_cap_checkpoint_restore.c  | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c b/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c
index 3c196fa86c99..976e92c259fc 100644
--- a/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c
+++ b/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c
@@ -53,9 +53,6 @@ static int call_clone3_set_tid(struct __test_metadata *_metadata,
 	}
 
 	if (pid == 0) {
-		int ret;
-		char tmp = 0;
-
 		TH_LOG("I am the child, my PID is %d (expected %d)", getpid(), set_tid[0]);
 
 		if (set_tid[0] != getpid())
@@ -135,7 +132,6 @@ TEST(clone3_cap_checkpoint_restore)
 {
 	pid_t pid;
 	int status;
-	int ret = 0;
 	pid_t set_tid[1];
 
 	test_clone3_supported();
-- 
2.45.2

[PATCH v2 02/13] selftests: ntsync: Fix build warnings

[Guenter Roeck]

Fix

ntsync.c:1286:20: warning: call to undeclared function 'gettid';
	ISO C99 and later do not support implicit function declarations
 1286 |         wait_args.owner = gettid();
      |                           ^
ntsync.c:1280:8: warning: unused variable 'index'
 1280 |         __u32 index, count, i;
      |               ^~~~~
ntsync.c:1281:6: warning: unused variable 'ret'
 1281 |         int ret;

by adding the missing include file and removing the unused variables.

Fixes: a22860e57b54 ("selftests: ntsync: Add a stress test for contended waits.")
Cc: Elizabeth Figura <zfigura@codeweavers.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2: Update subject and description to reflect that the patch fixes build
    warnings 

 tools/testing/selftests/drivers/ntsync/ntsync.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/drivers/ntsync/ntsync.c b/tools/testing/selftests/drivers/ntsync/ntsync.c
index 3aad311574c4..d3df94047e4d 100644
--- a/tools/testing/selftests/drivers/ntsync/ntsync.c
+++ b/tools/testing/selftests/drivers/ntsync/ntsync.c
@@ -11,6 +11,7 @@
 #include <fcntl.h>
 #include <time.h>
 #include <pthread.h>
+#include <unistd.h>
 #include <linux/ntsync.h>
 #include "../../kselftest_harness.h"
 
@@ -1277,8 +1278,7 @@ static int stress_device, stress_start_event, stress_mutex;
 static void *stress_thread(void *arg)
 {
 	struct ntsync_wait_args wait_args = {0};
-	__u32 index, count, i;
-	int ret;
+	__u32 count, i;
 
 	wait_args.timeout = UINT64_MAX;
 	wait_args.count = 1;
-- 
2.45.2

Re: [PATCH v2 02/13] selftests: ntsync: Fix build warnings

[Elizabeth Figura]

On Friday, 5 December 2025 11:09:56 CST Guenter Roeck wrote:
> Fix
> 
> ntsync.c:1286:20: warning: call to undeclared function 'gettid';
> 	ISO C99 and later do not support implicit function declarations
>  1286 |         wait_args.owner = gettid();
>       |                           ^
> ntsync.c:1280:8: warning: unused variable 'index'
>  1280 |         __u32 index, count, i;
>       |               ^~~~~
> ntsync.c:1281:6: warning: unused variable 'ret'
>  1281 |         int ret;
> 
> by adding the missing include file and removing the unused variables.
> 
> Fixes: a22860e57b54 ("selftests: ntsync: Add a stress test for contended waits.")
> Cc: Elizabeth Figura <zfigura@codeweavers.com>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
> v2: Update subject and description to reflect that the patch fixes build
>     warnings 
> 
>  tools/testing/selftests/drivers/ntsync/ntsync.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/drivers/ntsync/ntsync.c b/tools/testing/selftests/drivers/ntsync/ntsync.c
> index 3aad311574c4..d3df94047e4d 100644
> --- a/tools/testing/selftests/drivers/ntsync/ntsync.c
> +++ b/tools/testing/selftests/drivers/ntsync/ntsync.c
> @@ -11,6 +11,7 @@
>  #include <fcntl.h>
>  #include <time.h>
>  #include <pthread.h>
> +#include <unistd.h>
>  #include <linux/ntsync.h>
>  #include "../../kselftest_harness.h"
>  
> @@ -1277,8 +1278,7 @@ static int stress_device, stress_start_event, stress_mutex;
>  static void *stress_thread(void *arg)
>  {
>  	struct ntsync_wait_args wait_args = {0};
> -	__u32 index, count, i;
> -	int ret;
> +	__u32 count, i;
>  
>  	wait_args.timeout = UINT64_MAX;
>  	wait_args.count = 1;
> 

LGTM.

Reviewed-by: Elizabeth Figura <zfigura@codeweavers.com>

[PATCH v2 03/13] selftests/filesystems: fclog: Fix build warnings and errors

[Guenter Roeck]

Fix

fclog.c:37:21: warning: call to undeclared function 'open'
fclog.c:37:47: error: use of undeclared identifier 'O_RDONLY'; did you mean 'MS_RDONLY'?
fclog.c:37:56: error: use of undeclared identifier 'O_CLOEXEC'

by including fcntl.h.

Fixes: df579e471111b ("selftests/filesystems: add basic fscontext log tests")
Cc: Aleksa Sarai <cyphar@cyphar.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2: Update subject and description to reflect that the patch also fixes
    build warnings.

 tools/testing/selftests/filesystems/fclog.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/testing/selftests/filesystems/fclog.c b/tools/testing/selftests/filesystems/fclog.c
index 912a8b755c3b..d7cc3aaa8672 100644
--- a/tools/testing/selftests/filesystems/fclog.c
+++ b/tools/testing/selftests/filesystems/fclog.c
@@ -6,6 +6,7 @@
 
 #include <assert.h>
 #include <errno.h>
+#include <fcntl.h>
 #include <sched.h>
 #include <stdio.h>
 #include <stdlib.h>
-- 
2.45.2

[PATCH v2 04/13] selftests/filesystems: file_stressor: Fix build warning

[Guenter Roeck]

Fix

file_stressor.c:112:9: warning: unused variable 'pid_self'

by dropping the unused variable.

Fixes: aab154a442f9b ("selftests: add file SLAB_TYPESAFE_BY_RCU recycling stressor")
Cc: Christian Brauner <brauner@kernel.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2: Update subject and description to reflect that the patch fixes a build
    warning. 

 tools/testing/selftests/filesystems/file_stressor.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/tools/testing/selftests/filesystems/file_stressor.c b/tools/testing/selftests/filesystems/file_stressor.c
index 01dd89f8e52f..4f314270298d 100644
--- a/tools/testing/selftests/filesystems/file_stressor.c
+++ b/tools/testing/selftests/filesystems/file_stressor.c
@@ -109,8 +109,6 @@ FIXTURE_TEARDOWN(file_stressor)
 TEST_F_TIMEOUT(file_stressor, slab_typesafe_by_rcu, 900 * 2)
 {
 	for (int i = 0; i < self->nr_procs; i++) {
-		pid_t pid_self;
-
 		self->pids_openers[i] = fork();
 		ASSERT_GE(self->pids_openers[i], 0);
 
-- 
2.45.2

[PATCH v2 05/13] selftests/filesystems: anon_inode_test: Fix build warning

[Guenter Roeck]

Fix

anon_inode_test.c:45:12: warning: call to undeclared function 'execveat'

by adding the missing include file.

Fixes: f8ca403ae77cb ("selftests/filesystems: add exec() test for anonymous inodes")
Cc: Christian Brauner <brauner@kernel.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2: Update subject and description to reflect that the patch fixes a build
    warning.
    This patch does not fix:
	anon_inode_test.c: In function ‘anon_inode_no_exec’:
	anon_inode_test.c:46:19: warning: argument 3 null where non-null expected
    because I have no idea how to do avoid that warning.

 tools/testing/selftests/filesystems/anon_inode_test.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/testing/selftests/filesystems/anon_inode_test.c b/tools/testing/selftests/filesystems/anon_inode_test.c
index 73e0a4d4fb2f..5ddcfd2927f9 100644
--- a/tools/testing/selftests/filesystems/anon_inode_test.c
+++ b/tools/testing/selftests/filesystems/anon_inode_test.c
@@ -4,6 +4,7 @@
 
 #include <fcntl.h>
 #include <stdio.h>
+#include <unistd.h>
 #include <sys/stat.h>
 
 #include "../kselftest_harness.h"
-- 
2.45.2

[PATCH v2 06/13] selftest: af_unix: Support compilers without flex-array-member-not-at-end support

[Guenter Roeck]

Fix:

gcc: error: unrecognized command-line option ‘-Wflex-array-member-not-at-end’

by making the compiler option dependent on its support.

Fixes: 1838731f1072c ("selftest: af_unix: Add -Wall and -Wflex-array-member-not-at-end to CFLAGS.")
Cc: Kuniyuki Iwashima <kuniyu@google.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2: Just using cc-option is insufficient since it is not defined,
    and if it is not defined it just disables the option entirely.
    Include Makefile.compiler and declare the function locally
    to solve the problem.

 tools/testing/selftests/net/af_unix/Makefile | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/net/af_unix/Makefile b/tools/testing/selftests/net/af_unix/Makefile
index 3cd677b72072..4c0375e28bbe 100644
--- a/tools/testing/selftests/net/af_unix/Makefile
+++ b/tools/testing/selftests/net/af_unix/Makefile
@@ -1,4 +1,9 @@
-CFLAGS += $(KHDR_INCLUDES) -Wall -Wflex-array-member-not-at-end
+top_srcdir := ../../../../..
+include $(top_srcdir)/scripts/Makefile.compiler
+
+cc-option = $(call __cc-option, $(CC),,$(1),$(2))
+
+CFLAGS += $(KHDR_INCLUDES) -Wall $(call cc-option,-Wflex-array-member-not-at-end)
 
 TEST_GEN_PROGS := \
 	diag_uid \
-- 
2.45.2

[PATCH v2 07/13] selftest/futex: Comment out test_futex_mpol

[Guenter Roeck]

test_futex_mpol() is not called, resulting in the following build warning.

futex_numa_mpol.c:134:13: warning: ‘test_futex_mpol’ defined but not used

Disable the function but keep it in case it was supposed to be used.

Fixes: d35ca2f64272 ("selftests/futex: Refactor futex_numa_mpol with kselftest_harness.h")
Cc: André Almeida <andrealmeid@igalia.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2: Update subject and description to reflect that the patch fixes a build
    warning. 

 tools/testing/selftests/futex/functional/futex_numa_mpol.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/testing/selftests/futex/functional/futex_numa_mpol.c b/tools/testing/selftests/futex/functional/futex_numa_mpol.c
index d037a3f10ee8..8e3d17d66684 100644
--- a/tools/testing/selftests/futex/functional/futex_numa_mpol.c
+++ b/tools/testing/selftests/futex/functional/futex_numa_mpol.c
@@ -131,10 +131,12 @@ static void test_futex(void *futex_ptr, int err_value)
 	__test_futex(futex_ptr, err_value, FUTEX2_SIZE_U32 | FUTEX_PRIVATE_FLAG | FUTEX2_NUMA);
 }
 
+#ifdef NOTUSED
 static void test_futex_mpol(void *futex_ptr, int err_value)
 {
 	__test_futex(futex_ptr, err_value, FUTEX2_SIZE_U32 | FUTEX_PRIVATE_FLAG | FUTEX2_NUMA | FUTEX2_MPOL);
 }
+#endif
 
 TEST(futex_numa_mpol)
 {
-- 
2.45.2

[PATCH v2 08/13] selftests: net: netlink-dumps: Avoid uninitialized variable warning

[Guenter Roeck]

The following warning is seen when building netlink-dumps.

netlink-dumps.c: In function ‘dump_extack’:
../kselftest_harness.h:788:35: warning: ‘ret’ may be used uninitialized

Problem is that the loop which initializes 'ret' may exit early without
initializing the variable if recv() returns an error. Always initialize
'ret' to solve the problem.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2: Update subject and description to reflect that the patch fixes a build
    warning. 

 tools/testing/selftests/net/netlink-dumps.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/net/netlink-dumps.c b/tools/testing/selftests/net/netlink-dumps.c
index 679b6c77ace7..67bf3fc2d66b 100644
--- a/tools/testing/selftests/net/netlink-dumps.c
+++ b/tools/testing/selftests/net/netlink-dumps.c
@@ -112,7 +112,7 @@ static const struct {
 TEST(dump_extack)
 {
 	int netlink_sock;
-	int i, cnt, ret;
+	int i, cnt, ret = FOUND_ERR;
 	char buf[8192];
 	int one = 1;
 	ssize_t n;
-- 
2.45.2

Re: [PATCH v2 08/13] selftests: net: netlink-dumps: Avoid uninitialized variable warning

[Jakub Kicinski]

On Fri,  5 Dec 2025 09:10:02 -0800 Guenter Roeck wrote:
> The following warning is seen when building netlink-dumps.
> 
> netlink-dumps.c: In function ‘dump_extack’:
> ../kselftest_harness.h:788:35: warning: ‘ret’ may be used uninitialized
> 
> Problem is that the loop which initializes 'ret' may exit early without
> initializing the variable if recv() returns an error. Always initialize
> 'ret' to solve the problem.

Are you sure you're working off the latest tree? I think this should
already be fixed by 13cb6ac5b50

I applied the other 3 networking changes.

Re: [PATCH v2 08/13] selftests: net: netlink-dumps: Avoid uninitialized variable warning

[Guenter Roeck]

On 12/10/25 01:13, Jakub Kicinski wrote:
> On Fri,  5 Dec 2025 09:10:02 -0800 Guenter Roeck wrote:
>> The following warning is seen when building netlink-dumps.
>>
>> netlink-dumps.c: In function ‘dump_extack’:
>> ../kselftest_harness.h:788:35: warning: ‘ret’ may be used uninitialized
>>
>> Problem is that the loop which initializes 'ret' may exit early without
>> initializing the variable if recv() returns an error. Always initialize
>> 'ret' to solve the problem.
> 
> Are you sure you're working off the latest tree? I think this should
> already be fixed by 13cb6ac5b50
> 

Sorry for missing the fix. I was working off v6.18, which was the tip of
the tree when I wrote the patch.

> I applied the other 3 networking changes.

Thanks a lot!

Guenter

[PATCH v2 09/13] selftests/seccomp: Fix build warning

[Guenter Roeck]

Fix:

seccomp_bpf.c: In function ‘UPROBE_setup’:
seccomp_bpf.c:5175:74: warning: pointer type mismatch in conditional expression

by type casting the argument to get_uprobe_offset().

Fixes: 9ffc7a635c35a ("selftests/seccomp: validate uprobe syscall passes through seccomp")
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2: Update subject and description to reflect that the patch fixes a build
    warning. 

 tools/testing/selftests/seccomp/seccomp_bpf.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
index 874f17763536..2584f4f5c062 100644
--- a/tools/testing/selftests/seccomp/seccomp_bpf.c
+++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
@@ -5172,7 +5172,8 @@ FIXTURE_SETUP(UPROBE)
 		ASSERT_GE(bit, 0);
 	}
 
-	offset = get_uprobe_offset(variant->uretprobe ? probed_uretprobe : probed_uprobe);
+	offset = get_uprobe_offset(variant->uretprobe ?
+				   (void *)probed_uretprobe : (void *)probed_uprobe);
 	ASSERT_GE(offset, 0);
 
 	if (variant->uretprobe)
-- 
2.45.2

Re: [PATCH v2 09/13] selftests/seccomp: Fix build warning

[Kees Cook]

On Fri, Dec 05, 2025 at 09:10:03AM -0800, Guenter Roeck wrote:
> Fix:
> 
> seccomp_bpf.c: In function ‘UPROBE_setup’:
> seccomp_bpf.c:5175:74: warning: pointer type mismatch in conditional expression
> 
> by type casting the argument to get_uprobe_offset().
> 
> Fixes: 9ffc7a635c35a ("selftests/seccomp: validate uprobe syscall passes through seccomp")
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Reviewed-by: Kees Cook <kees@kernel.org>

-- 
Kees Cook

[PATCH v2 10/13] selftests: net: Fix build warnings

[Guenter Roeck]

Fix

ksft.h: In function ‘ksft_ready’:
ksft.h:27:9: warning: ignoring return value of ‘write’ declared with attribute ‘warn_unused_result’

ksft.h: In function ‘ksft_wait’:
ksft.h:51:9: warning: ignoring return value of ‘read’ declared with attribute ‘warn_unused_result’

by checking the return value of the affected functions and displaying
an error message if an error is seen.

Fixes: 2b6d490b82668 ("selftests: drv-net: Factor out ksft C helpers")
Cc: Joe Damato <jdamato@fastly.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2: Update subject and description to reflect that the patch fixes build
    warnings.
    Use perror() to display an error message if one of the functions
    returns an error.

 tools/testing/selftests/net/lib/ksft.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/net/lib/ksft.h b/tools/testing/selftests/net/lib/ksft.h
index 17dc34a612c6..03912902a6d3 100644
--- a/tools/testing/selftests/net/lib/ksft.h
+++ b/tools/testing/selftests/net/lib/ksft.h
@@ -24,7 +24,8 @@ static inline void ksft_ready(void)
 		fd = STDOUT_FILENO;
 	}
 
-	write(fd, msg, sizeof(msg));
+	if (write(fd, msg, sizeof(msg)) < 0)
+		perror("write()");
 	if (fd != STDOUT_FILENO)
 		close(fd);
 }
@@ -48,7 +49,8 @@ static inline void ksft_wait(void)
 		fd = STDIN_FILENO;
 	}
 
-	read(fd, &byte, sizeof(byte));
+	if (read(fd, &byte, sizeof(byte)) < 0)
+		perror("read()");
 	if (fd != STDIN_FILENO)
 		close(fd);
 }
-- 
2.45.2

[PATCH v2 11/13] selftests/fs/mount-notify: Fix build warning

[Guenter Roeck]

Fix

mount-notify_test.c: In function ‘fanotify_rmdir’:
mount-notify_test.c:467:17: warning:
	ignoring return value of ‘chdir’ declared with attribute ‘warn_unused_result’

by checking the return value of chdir() and displaying an error message
if an error is reported.

Fixes: e1c24b52adb22 ("selftests: add tests for mount notification")
Cc: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2: Update subject and description to reflect that the patch fixes a build
    warning.
    Use perror() to display an error message if chdir() returns an error.

 .../selftests/filesystems/mount-notify/mount-notify_test.c     | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/filesystems/mount-notify/mount-notify_test.c b/tools/testing/selftests/filesystems/mount-notify/mount-notify_test.c
index e4b7c2b457ee..5c929275e689 100644
--- a/tools/testing/selftests/filesystems/mount-notify/mount-notify_test.c
+++ b/tools/testing/selftests/filesystems/mount-notify/mount-notify_test.c
@@ -464,7 +464,8 @@ TEST_F(fanotify, rmdir)
 	ASSERT_GE(ret, 0);
 
 	if (ret == 0) {
-		chdir("/");
+		if (chdir("/"))
+			perror("chdir()");
 		unshare(CLONE_NEWNS);
 		mount("", "/", NULL, MS_REC|MS_PRIVATE, NULL);
 		umount2("/a", MNT_DETACH);
-- 
2.45.2

[PATCH v2 12/13] selftests/fs/mount-notify-ns: Fix build warning

[Guenter Roeck]

Fix

mount-notify_test_ns.c: In function ‘fanotify_rmdir’:
mount-notify_test_ns.c:494:17: warning:
	ignoring return value of ‘chdir’ declared with attribute ‘warn_unused_result’

by checking the return value of chdir() and displaying an error message
if it returns an error.

Fixes: 781091f3f5945 ("selftests/fs/mount-notify: add a test variant running inside userns")
Cc: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2: Update subject and description to reflect that the patch fixes a build
    warning.
    Use perror() to display an error message if chdir() returns an error.

 .../selftests/filesystems/mount-notify/mount-notify_test_ns.c  | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/filesystems/mount-notify/mount-notify_test_ns.c b/tools/testing/selftests/filesystems/mount-notify/mount-notify_test_ns.c
index 9f57ca46e3af..90bec6faf64e 100644
--- a/tools/testing/selftests/filesystems/mount-notify/mount-notify_test_ns.c
+++ b/tools/testing/selftests/filesystems/mount-notify/mount-notify_test_ns.c
@@ -491,7 +491,8 @@ TEST_F(fanotify, rmdir)
 	ASSERT_GE(ret, 0);
 
 	if (ret == 0) {
-		chdir("/");
+		if (chdir("/"))
+			perror("chdir()");
 		unshare(CLONE_NEWNS);
 		mount("", "/", NULL, MS_REC|MS_PRIVATE, NULL);
 		umount2("/a", MNT_DETACH);
-- 
2.45.2

Re: [PATCH v2 12/13] selftests/fs/mount-notify-ns: Fix build warning

[Amir Goldstein]

On Fri, Dec 5, 2025 at 6:12 PM Guenter Roeck <linux@roeck-us.net> wrote:
>
> Fix
>
> mount-notify_test_ns.c: In function ‘fanotify_rmdir’:
> mount-notify_test_ns.c:494:17: warning:
>         ignoring return value of ‘chdir’ declared with attribute ‘warn_unused_result’
>
> by checking the return value of chdir() and displaying an error message
> if it returns an error.
>
> Fixes: 781091f3f5945 ("selftests/fs/mount-notify: add a test variant running inside userns")
> Cc: Amir Goldstein <amir73il@gmail.com>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
> v2: Update subject and description to reflect that the patch fixes a build
>     warning.
>     Use perror() to display an error message if chdir() returns an error.
>
>  .../selftests/filesystems/mount-notify/mount-notify_test_ns.c  | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/filesystems/mount-notify/mount-notify_test_ns.c b/tools/testing/selftests/filesystems/mount-notify/mount-notify_test_ns.c
> index 9f57ca46e3af..90bec6faf64e 100644
> --- a/tools/testing/selftests/filesystems/mount-notify/mount-notify_test_ns.c
> +++ b/tools/testing/selftests/filesystems/mount-notify/mount-notify_test_ns.c
> @@ -491,7 +491,8 @@ TEST_F(fanotify, rmdir)
>         ASSERT_GE(ret, 0);
>
>         if (ret == 0) {
> -               chdir("/");
> +               if (chdir("/"))
> +                       perror("chdir()");

ASSERT_EQ(0, chdir("/"));

and there is another one like this in mount-notify_test.c

Thanks,
Amir.

Re: [PATCH v2 12/13] selftests/fs/mount-notify-ns: Fix build warning

[Guenter Roeck]

On 12/5/25 09:31, Amir Goldstein wrote:
> On Fri, Dec 5, 2025 at 6:12 PM Guenter Roeck <linux@roeck-us.net> wrote:
>>
>> Fix
>>
>> mount-notify_test_ns.c: In function ‘fanotify_rmdir’:
>> mount-notify_test_ns.c:494:17: warning:
>>          ignoring return value of ‘chdir’ declared with attribute ‘warn_unused_result’
>>
>> by checking the return value of chdir() and displaying an error message
>> if it returns an error.
>>
>> Fixes: 781091f3f5945 ("selftests/fs/mount-notify: add a test variant running inside userns")
>> Cc: Amir Goldstein <amir73il@gmail.com>
>> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
>> ---
>> v2: Update subject and description to reflect that the patch fixes a build
>>      warning.
>>      Use perror() to display an error message if chdir() returns an error.
>>
>>   .../selftests/filesystems/mount-notify/mount-notify_test_ns.c  | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/testing/selftests/filesystems/mount-notify/mount-notify_test_ns.c b/tools/testing/selftests/filesystems/mount-notify/mount-notify_test_ns.c
>> index 9f57ca46e3af..90bec6faf64e 100644
>> --- a/tools/testing/selftests/filesystems/mount-notify/mount-notify_test_ns.c
>> +++ b/tools/testing/selftests/filesystems/mount-notify/mount-notify_test_ns.c
>> @@ -491,7 +491,8 @@ TEST_F(fanotify, rmdir)
>>          ASSERT_GE(ret, 0);
>>
>>          if (ret == 0) {
>> -               chdir("/");
>> +               if (chdir("/"))
>> +                       perror("chdir()");
> 
> ASSERT_EQ(0, chdir("/"));
> 
> and there is another one like this in mount-notify_test.c
> 

Done.

Thanks,
Guenter

[PATCH v2 13/13] selftests: net: tfo: Fix build warning

[Guenter Roeck]

Fix

tfo.c: In function ‘run_server’:
tfo.c:84:9: warning: ignoring return value of ‘read’ declared with attribute ‘warn_unused_result’

by evaluating the return value from read() and displaying an error message
if it reports an error.

Fixes: c65b5bb2329e3 ("selftests: net: add passive TFO test binary")
Cc: David Wei <dw@davidwei.uk>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2: Update subject and description to reflect that the patch fixes a build
    warning.
    Use perror() to display an error message if read() returns an error.

 tools/testing/selftests/net/tfo.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/net/tfo.c b/tools/testing/selftests/net/tfo.c
index eb3cac5e583c..8d82140f0f76 100644
--- a/tools/testing/selftests/net/tfo.c
+++ b/tools/testing/selftests/net/tfo.c
@@ -81,7 +81,8 @@ static void run_server(void)
 	if (getsockopt(connfd, SOL_SOCKET, SO_INCOMING_NAPI_ID, &opt, &len) < 0)
 		error(1, errno, "getsockopt(SO_INCOMING_NAPI_ID)");
 
-	read(connfd, buf, 64);
+	if (read(connfd, buf, 64) < 0)
+		perror("read()");
 	fprintf(outfile, "%d\n", opt);
 
 	fclose(outfile);
-- 
2.45.2

Re: [PATCH v2 00/13] selftests: Fix build warnings and errors

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Fri,  5 Dec 2025 09:09:54 -0800 you wrote:
> This series fixes build warnings and errors observed when trying to build
> selftests.
> 
> v2: Emphasize that the patch series fixes build warnings and errors
>     which are seen even if -Werror is not provided.
>     Fix usage of cc-option.
>     For "ignoring return value" warnings, use perror() to display an error
>     message if the affected function returns an error.
> 
> [...]

Here is the summary with links:
  - [v2,01/13] clone3: clone3_cap_checkpoint_restore: Fix build warnings
    (no matching commit)
  - [v2,02/13] selftests: ntsync: Fix build warnings
    (no matching commit)
  - [v2,03/13] selftests/filesystems: fclog: Fix build warnings and errors
    (no matching commit)
  - [v2,04/13] selftests/filesystems: file_stressor: Fix build warning
    (no matching commit)
  - [v2,05/13] selftests/filesystems: anon_inode_test: Fix build warning
    (no matching commit)
  - [v2,06/13] selftest: af_unix: Support compilers without flex-array-member-not-at-end support
    https://git.kernel.org/netdev/net/c/06f7cae92fe3
  - [v2,07/13] selftest/futex: Comment out test_futex_mpol
    (no matching commit)
  - [v2,08/13] selftests: net: netlink-dumps: Avoid uninitialized variable warning
    (no matching commit)
  - [v2,09/13] selftests/seccomp: Fix build warning
    (no matching commit)
  - [v2,10/13] selftests: net: Fix build warnings
    https://git.kernel.org/netdev/net/c/59546e874403
  - [v2,11/13] selftests/fs/mount-notify: Fix build warning
    (no matching commit)
  - [v2,12/13] selftests/fs/mount-notify-ns: Fix build warning
    (no matching commit)
  - [v2,13/13] selftests: net: tfo: Fix build warning
    https://git.kernel.org/netdev/net/c/91dc09a609d9

You are awesome, thank you!
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