Compiler reports potential uses of uninitialized variables in
mptcp_connect.c when xerror() is called from failure paths.

mptcp_connect.c:1262:11: warning: variable 'raw_addr' is used
      uninitialized whenever 'if' condition is false
      [-Wsometimes-uninitialized]

xerror() terminates execution by calling exit(), but it is not visible
to the compiler & assumes control flow may continue past the call.

Annotate xerror() with __noreturn so the compiler can correctly reason
about control flow and avoid false-positive uninitialized variable
warnings.

Signed-off-by: Ankit Khushwaha <ankitkhushwaha.linux@gmail.com>
---
changelog:
v3:
- also annotate 'die_perror()' with __noreturn
- add CFLAGS at top of makefile
- target this patch to net instead of net-next as suggested by Matthieu

v2: https://lore.kernel.org/all/20251129043808.16714-1-ankitkhushwaha.linux@gmail.com/
- annotate 'xerror()' with __noreturn
- remove defining 'raw_addr' to NULL

v1: https://lore.kernel.org/all/20251126163046.58615-1-ankitkhushwaha.linux@gmail.com/
---
 tools/testing/selftests/net/mptcp/Makefile        | 1 +
 tools/testing/selftests/net/mptcp/mptcp_connect.c | 3 ++-
 tools/testing/selftests/net/mptcp/mptcp_diag.c    | 3 ++-
 tools/testing/selftests/net/mptcp/mptcp_inq.c     | 5 +++--
 tools/testing/selftests/net/mptcp/mptcp_sockopt.c | 5 +++--
 5 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/net/mptcp/Makefile b/tools/testing/selftests/net/mptcp/Makefile
index 15d144a25d82..4dd6278cd3dd 100644
--- a/tools/testing/selftests/net/mptcp/Makefile
+++ b/tools/testing/selftests/net/mptcp/Makefile
@@ -3,6 +3,7 @@
 top_srcdir = ../../../../..

 CFLAGS += -Wall -Wl,--no-as-needed -O2 -g -I$(top_srcdir)/usr/include $(KHDR_INCLUDES)
+CFLAGS += -I$(top_srcdir)/tools/include

 TEST_PROGS := \
 	diag.sh \
diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect.c b/tools/testing/selftests/net/mptcp/mptcp_connect.c
index 404a77bf366a..10f6f99cfd4e 100644
--- a/tools/testing/selftests/net/mptcp/mptcp_connect.c
+++ b/tools/testing/selftests/net/mptcp/mptcp_connect.c
@@ -33,6 +33,7 @@
 #include <linux/tcp.h>
 #include <linux/time_types.h>
 #include <linux/sockios.h>
+#include <linux/compiler.h>

 extern int optind;

@@ -140,7 +141,7 @@ static void die_usage(void)
 	exit(1);
 }

-static void xerror(const char *fmt, ...)
+static void __noreturn xerror(const char *fmt, ...)
 {
 	va_list ap;

diff --git a/tools/testing/selftests/net/mptcp/mptcp_diag.c b/tools/testing/selftests/net/mptcp/mptcp_diag.c
index e084796e804d..8e0b1b8d84b6 100644
--- a/tools/testing/selftests/net/mptcp/mptcp_diag.c
+++ b/tools/testing/selftests/net/mptcp/mptcp_diag.c
@@ -5,6 +5,7 @@
 #include <linux/rtnetlink.h>
 #include <linux/inet_diag.h>
 #include <linux/netlink.h>
+#include <linux/compiler.h>
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <linux/tcp.h>
@@ -87,7 +88,7 @@ enum {

 #define rta_getattr(type, value)		(*(type *)RTA_DATA(value))

-static void die_perror(const char *msg)
+static void __noreturn die_perror(const char *msg)
 {
 	perror(msg);
 	exit(1);
diff --git a/tools/testing/selftests/net/mptcp/mptcp_inq.c b/tools/testing/selftests/net/mptcp/mptcp_inq.c
index 8e8f6441ad8b..5716998da192 100644
--- a/tools/testing/selftests/net/mptcp/mptcp_inq.c
+++ b/tools/testing/selftests/net/mptcp/mptcp_inq.c
@@ -28,6 +28,7 @@

 #include <linux/tcp.h>
 #include <linux/sockios.h>
+#include <linux/compiler.h>

 #ifndef IPPROTO_MPTCP
 #define IPPROTO_MPTCP 262
@@ -40,7 +41,7 @@ static int pf = AF_INET;
 static int proto_tx = IPPROTO_MPTCP;
 static int proto_rx = IPPROTO_MPTCP;

-static void die_perror(const char *msg)
+static void __noreturn die_perror(const char *msg)
 {
 	perror(msg);
 	exit(1);
@@ -52,7 +53,7 @@ static void die_usage(int r)
 	exit(r);
 }

-static void xerror(const char *fmt, ...)
+static void __noreturn xerror(const char *fmt, ...)
 {
 	va_list ap;

diff --git a/tools/testing/selftests/net/mptcp/mptcp_sockopt.c b/tools/testing/selftests/net/mptcp/mptcp_sockopt.c
index 286164f7246e..b6e58d936ebe 100644
--- a/tools/testing/selftests/net/mptcp/mptcp_sockopt.c
+++ b/tools/testing/selftests/net/mptcp/mptcp_sockopt.c
@@ -25,6 +25,7 @@
 #include <netinet/in.h>

 #include <linux/tcp.h>
+#include <linux/compiler.h>

 static int pf = AF_INET;

@@ -127,7 +128,7 @@ struct so_state {
 #define MIN(a, b) ((a) < (b) ? (a) : (b))
 #endif

-static void die_perror(const char *msg)
+static void __noreturn die_perror(const char *msg)
 {
 	perror(msg);
 	exit(1);
@@ -139,7 +140,7 @@ static void die_usage(int r)
 	exit(r);
 }

-static void xerror(const char *fmt, ...)
+static void __noreturn xerror(const char *fmt, ...)
 {
 	va_list ap;

--
2.52.0

Hello:

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

On Thu,  1 Jan 2026 22:58:40 +0530 you wrote:
> Compiler reports potential uses of uninitialized variables in
> mptcp_connect.c when xerror() is called from failure paths.
> 
> mptcp_connect.c:1262:11: warning: variable 'raw_addr' is used
>       uninitialized whenever 'if' condition is false
>       [-Wsometimes-uninitialized]
> 
> [...]

Here is the summary with links:
  - [net,v3] selftests: mptcp: Mark xerror and die_perror __noreturn
    https://git.kernel.org/netdev/net/c/2fa98059fd5a

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Hi Ankit,

Thank you for your modifications, that's great!

Our CI did some validations and here is its report:

- KVM Validation: normal (except selftest_mptcp_join): Success! ✅
- KVM Validation: normal (only selftest_mptcp_join): Success! ✅
- KVM Validation: debug (except selftest_mptcp_join): Success! ✅
- KVM Validation: debug (only selftest_mptcp_join): Success! ✅
- KVM Validation: btf-normal (only bpftest_all): Success! ✅
- KVM Validation: btf-debug (only bpftest_all): Success! ✅
- Task: https://github.com/multipath-tcp/mptcp_net-next/actions/runs/20642822498

Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/4b6275a5aee6
Patchwork: https://patchwork.kernel.org/project/mptcp/list/?series=1037823


If there are some issues, you can reproduce them using the same environment as
the one used by the CI thanks to a docker image, e.g.:

    $ cd [kernel source code]
    $ docker run -v "${PWD}:${PWD}:rw" -w "${PWD}" --privileged --rm -it \
        --pull always mptcp/mptcp-upstream-virtme-docker:latest \
        auto-normal

For more details:

    https://github.com/multipath-tcp/mptcp-upstream-virtme-docker


Please note that despite all the efforts that have been already done to have a
stable tests suite when executed on a public CI like here, it is possible some
reported issues are not due to your modifications. Still, do not hesitate to
help us improve that ;-)

Cheers,
MPTCP GH Action bot
Bot operated by Matthieu Baerts (NGI0 Core)