The "void *raw_addr" is left uninitialized when else path is followed raising below warning.
mptcp_connect.c:1262:11: warning: variable 'raw_addr' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
so the fix is to assign *raw_addr to NULL to suppress the warning.
Signed-off-by: Ankit Khushwaha ankitkhushwaha.linux@gmail.com --- compiler used: clang version 21.1.5 (Fedora 21.1.5-1.fc43). compilation cmd used: make -C tools/testing/selftests/net/mptcp CC=clang V=1 -j8
this maybe also be false positive. But somehow clang - 21.1.5 triggering this.
--- tools/testing/selftests/net/mptcp/mptcp_connect.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect.c b/tools/testing/selftests/net/mptcp/mptcp_connect.c index 404a77bf366a..cdb81e0d08ad 100644 --- a/tools/testing/selftests/net/mptcp/mptcp_connect.c +++ b/tools/testing/selftests/net/mptcp/mptcp_connect.c @@ -1248,8 +1248,8 @@ void xdisconnect(int fd) { socklen_t addrlen = sizeof(struct sockaddr_storage); struct sockaddr_storage addr, empty; + void *raw_addr = NULL; int msec_sleep = 10; - void *raw_addr; int i, cmdlen; char cmd[128];
-- 2.52.0
Hi Ankit,
On 26/11/2025 17:30, Ankit Khushwaha wrote:
The "void *raw_addr" is left uninitialized when else path is followed raising below warning.
mptcp_connect.c:1262:11: warning: variable 'raw_addr' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
so the fix is to assign *raw_addr to NULL to suppress the warning.
Thank you for having shared this patch!
Signed-off-by: Ankit Khushwaha ankitkhushwaha.linux@gmail.com
compiler used: clang version 21.1.5 (Fedora 21.1.5-1.fc43). compilation cmd used: make -C tools/testing/selftests/net/mptcp CC=clang V=1 -j8
this maybe also be false positive. But somehow clang - 21.1.5 triggering this.
I confirm this, I can reproduce the warning with Clang 21.
It is indeed a false positive, because the code does that:
if (addr.ss_family == AF_INET) raw_addr = &(((struct sockaddr_in *)&addr)->sin_addr); else if (addr.ss_family == AF_INET6) raw_addr = &(((struct sockaddr_in6 *)&addr)->sin6_addr); else xerror("bad family");
"xerror()" calls "exit(1)", so "raw_addr" is never used uninitialized.
I'm not sure why Clang 21 reports that now, and not before, but well, the modification you did in the selftests doesn't hurt:
Reviewed-by: Matthieu Baerts (NGI0) matttbe@kernel.org
@Net maintainers: this patch can be applied in 'net' directly.
@Antik: next time, please specify the target (net/net-next) in the subject, see [1]. No need to send a new version (except if the Net maintainers prefer), this patch can be applied on top of "net" without conflicts.
[1] https://docs.kernel.org/process/maintainer-netdev.html
Cheers, Matt
On Wed, 26 Nov 2025 17:55:14 +0100 Matthieu Baerts wrote:
I confirm this, I can reproduce the warning with Clang 21.
It is indeed a false positive, because the code does that:
if (addr.ss_family == AF_INET) raw_addr = &(((struct sockaddr_in *)&addr)->sin_addr); else if (addr.ss_family == AF_INET6) raw_addr = &(((struct sockaddr_in6 *)&addr)->sin6_addr); else xerror("bad family");
"xerror()" calls "exit(1)", so "raw_addr" is never used uninitialized.
I'm not sure why Clang 21 reports that now, and not before, but well, the modification you did in the selftests doesn't hurt:
I think annotating xerror with __noreturn is a better fix. Including kselftest.h will be needed.
Hi Jakub, Ankit,
On 28/11/2025 02:00, Jakub Kicinski wrote:
On Wed, 26 Nov 2025 17:55:14 +0100 Matthieu Baerts wrote:
I confirm this, I can reproduce the warning with Clang 21.
It is indeed a false positive, because the code does that:
if (addr.ss_family == AF_INET) raw_addr = &(((struct sockaddr_in *)&addr)->sin_addr); else if (addr.ss_family == AF_INET6) raw_addr = &(((struct sockaddr_in6 *)&addr)->sin6_addr); else xerror("bad family");
"xerror()" calls "exit(1)", so "raw_addr" is never used uninitialized.
I'm not sure why Clang 21 reports that now, and not before, but well, the modification you did in the selftests doesn't hurt:
I think annotating xerror with __noreturn is a better fix.
Good idea, I didn't know about that!
Thank you for the review!
Including kselftest.h will be needed.
Because mptcp_connect.c is a tool that is used by other selftests, but it doesn't interact directly with the selftests, maybe we don't need to include it, and only add this #define in mptcp_connect.c?
#define __noreturn __attribute__((__noreturn__))
(I don't know if a #ifndef/#endif is needed.)
That's a detail, I guess either is fine and shouldn't cause other issues.
Cheers, Matt
linux-kselftest-mirror@lists.linaro.org
-
Ankit Khushwaha -
Jakub Kicinski -
Matthieu Baerts