[PATCH net v3] selftests: mptcp: Mark xerror and die_perror __noreturn

Ankit Khushwaha
2026-01-01T17:28:58Z

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