linux-kernel - [PATCH] tipc: avoid a clang -Wuninitialized warning

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Date:   Fri, 22 Mar 2019 15:18:13 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Jon Maloy <jon.maloy@...csson.com>,
        Ying Xue <ying.xue@...driver.com>,
        "David S. Miller" <davem@...emloft.net>
Cc:     clang-built-linux@...glegroups.com,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        Tuong Lien <tuong.t.lien@...tech.com.au>,
        LUU Duc Canh <canh.d.luu@...tech.com.au>,
        Tung Nguyen <tung.q.nguyen@...tech.com.au>,
        GhantaKrishnamurthy MohanKrishna 
        <mohan.krishna.ghanta.krishnamurthy@...csson.com>,
        netdev@...r.kernel.org, tipc-discussion@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: [PATCH] tipc: avoid a clang -Wuninitialized warning

clang notices that we pass 'maddr' into the tipc_bearer_xmit() function
without having initialized it first:

net/tipc/node.c:831:6: error: variable 'maddr' is used uninitialized whenever 'if' condition is false
      [-Werror,-Wsometimes-uninitialized]
        if (!tipc_link_is_establishing(l)) {
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
net/tipc/node.c:847:46: note: uninitialized use occurs here
        tipc_bearer_xmit(n->net, bearer_id, &xmitq, maddr);
                                                    ^~~~~
net/tipc/node.c:831:2: note: remove the 'if' if its condition is always true
        if (!tipc_link_is_establishing(l)) {
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
net/tipc/node.c:821:31: note: initialize the variable 'maddr' to silence this warning
        struct tipc_media_addr *maddr;
                                     ^
                                      = NULL

This is harmless because it won't use 'maddr' if the
queue is empty, but it's better to make that explicit
and not even call the function in that case.

As clang is able to inline the check, it then notices that
the code is safe.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 net/tipc/node.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/tipc/node.c b/net/tipc/node.c
index 2dc4919ab23c..ca4cafd00a38 100644
--- a/net/tipc/node.c
+++ b/net/tipc/node.c
@@ -844,7 +844,8 @@ static void tipc_node_link_down(struct tipc_node *n, int bearer_id, bool delete)
 	tipc_node_write_unlock(n);
 	if (delete)
 		tipc_mon_remove_peer(n->net, n->addr, old_bearer_id);
-	tipc_bearer_xmit(n->net, bearer_id, &xmitq, maddr);
+	if (!skb_queue_empty(&xmitq))
+		tipc_bearer_xmit(n->net, bearer_id, &xmitq, maddr);
 	tipc_sk_rcv(n->net, &le->inputq);
 }
 
-- 
2.20.0