[PATCH] tipc: avoid a clang -Wuninitialized warning

[PATCH] tipc: avoid a clang -Wuninitialized warning

[Arnd Bergmann]

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@arndb.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

Re: [PATCH] tipc: avoid a clang -Wuninitialized warning

[Nathan Chancellor]

On Fri, Mar 22, 2019 at 03:18:13PM +0100, Arnd Bergmann wrote:
> 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@arndb.de>

Thanks for looking into this and fixing it!

Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>

> ---
>  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
> 

Re: [PATCH] tipc: avoid a clang -Wuninitialized warning

[David Miller]

From: Arnd Bergmann <arnd@arndb.de>
Date: Fri, 22 Mar 2019 15:18:13 +0100

> clang notices that we pass 'maddr' into the tipc_bearer_xmit() function
> without having initialized it first:
 ...
> 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@arndb.de>

It looks like Jon's patch took care of this.