linux-kernel - Re: [PATCH] rxrpc: avoid clang -Wuninitialized warning

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Date:   Fri, 22 Mar 2019 08:22:09 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     David Howells <dhowells@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        clang-built-linux@...glegroups.com,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        YueHaibing <yuehaibing@...wei.com>,
        linux-afs@...ts.infradead.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rxrpc: avoid clang -Wuninitialized warning

On Fri, Mar 22, 2019 at 03:18:43PM +0100, Arnd Bergmann wrote:
> clang produces a false-positive warning as it fails to notice
> that "lost = true" implies that "ret" is initialized:
> 
> net/rxrpc/output.c:402:6: error: variable 'ret' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
>         if (lost)
>             ^~~~
> net/rxrpc/output.c:437:6: note: uninitialized use occurs here
>         if (ret >= 0) {
>             ^~~
> net/rxrpc/output.c:402:2: note: remove the 'if' if its condition is always false
>         if (lost)
>         ^~~~~~~~~
> net/rxrpc/output.c:339:9: note: initialize the variable 'ret' to silence this warning
>         int ret, opt;
>                ^
>                 = 0
> 
> Rearrange the code to make that more obvious and avoid the warning.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

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

> ---
>  net/rxrpc/output.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/net/rxrpc/output.c b/net/rxrpc/output.c
> index 736aa9281100..004c762c2e8d 100644
> --- a/net/rxrpc/output.c
> +++ b/net/rxrpc/output.c
> @@ -335,7 +335,6 @@ int rxrpc_send_data_packet(struct rxrpc_call *call, struct sk_buff *skb,
>  	struct kvec iov[2];
>  	rxrpc_serial_t serial;
>  	size_t len;
> -	bool lost = false;
>  	int ret, opt;
>  
>  	_enter(",{%d}", skb->len);
> @@ -393,14 +392,14 @@ int rxrpc_send_data_packet(struct rxrpc_call *call, struct sk_buff *skb,
>  		static int lose;
>  		if ((lose++ & 7) == 7) {
>  			ret = 0;
> -			lost = true;
> +			trace_rxrpc_tx_data(call, sp->hdr.seq, serial,
> +					    whdr.flags, retrans, true);
> +			goto done;
>  		}
>  	}
>  
> -	trace_rxrpc_tx_data(call, sp->hdr.seq, serial, whdr.flags,
> -			    retrans, lost);
> -	if (lost)
> -		goto done;
> +	trace_rxrpc_tx_data(call, sp->hdr.seq, serial, whdr.flags, retrans,
> +			    false);
>  
>  	/* send the packet with the don't fragment bit set if we currently
>  	 * think it's small enough */
> -- 
> 2.20.0
>