-Wsometimes-uninitialized Clang warning in drivers/net/ethernet/broadcom/bnxt/bnxt.c

From: Nathan Chancellor <natechancellor@gmail.com>
To: Michael Chan <michael.chan@broadcom.com>,
	"David S. Miller" <davem@davemloft.net>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	Nick Desaulniers <ndesaulniers@google.com>,
	clang-built-linux@googlegroups.com
Subject: -Wsometimes-uninitialized Clang warning in drivers/net/ethernet/broadcom/bnxt/bnxt.c
Date: Thu, 7 Mar 2019 17:57:35 -0700	[thread overview]
Message-ID: <20190308005735.GA4122@archlinux-ryzen> (raw)

Hi all,

We are trying to get Clang's -Wsometimes-uninitialized turned on for the
kernel as it can catch some bugs that GCC can't. This warning came up:

drivers/net/ethernet/broadcom/bnxt/bnxt.c:1612:6: warning: variable 'len' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
        if (rxcmp1->rx_cmp_cfa_code_errors_v2 & RX_CMP_L2_ERRORS) {
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/broadcom/bnxt/bnxt.c:1703:19: note: uninitialized use occurs here
        cpr->rx_bytes += len;
                         ^~~
drivers/net/ethernet/broadcom/bnxt/bnxt.c:1612:2: note: remove the 'if' if its condition is always false
        if (rxcmp1->rx_cmp_cfa_code_errors_v2 & RX_CMP_L2_ERRORS) {
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/broadcom/bnxt/bnxt.c:1540:18: note: initialize the variable 'len' to silence this warning
        unsigned int len;
                        ^
                         = 0
1 warning generated.

It seems like the logical change to make is this; however, I am not sure
if this has any other unintended consequences since this is a rather
dense function. I would much appreciate your input, especially if there
is a better way to fix it.

Cheers,
Nathan

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index 0bb9d7b3a2b6..7d3d206c2e86 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -1615,7 +1615,7 @@ static int bnxt_rx_pkt(struct bnxt *bp, struct bnxt_cp_ring_info *cpr,
                        bnxt_reuse_rx_agg_bufs(cpr, cp_cons, agg_bufs);
 
                rc = -EIO;
-               goto next_rx;
+               goto next_rx_no_prod_no_len;
        }
 
        len = le32_to_cpu(rxcmp->rx_cmp_len_flags_type) >> RX_CMP_LEN_SHIFT;
