[ovs-dev] [PATCH V3 20/24] datapath: Distribute switch variables for initialization

[Yi-Hung Wei]

On Wed, Sep 16, 2020 at 10:35 AM Greg Rose <gvrose8192 at gmail.com> wrote:
>
> From: Kees Cook <keescook at chromium.org>
>
> Upstream commit:
>     commit 16a556eeb7ed2dc3709fe2c5be76accdfa4901ab
>     Author: Kees Cook <keescook at chromium.org>
>     Date:   Wed Feb 19 22:23:09 2020 -0800
>
>     openvswitch: Distribute switch variables for initialization
>
>     Variables declared in a switch statement before any case statements
>     cannot be automatically initialized with compiler instrumentation (as
>     they are not part of any execution flow). With GCC's proposed automatic
>     stack variable initialization feature, this triggers a warning (and they
>     don't get initialized). Clang's automatic stack variable initialization
>     (via CONFIG_INIT_STACK_ALL=y) doesn't throw a warning, but it also
>     doesn't initialize such variables[1]. Note that these warnings (or silent
>     skipping) happen before the dead-store elimination optimization phase,
>     so even when the automatic initializations are later elided in favor of
>     direct initializations, the warnings remain.
>
>     To avoid these problems, move such variables into the "case" where
>     they're used or lift them up into the main function body.
>
>     net/openvswitch/flow_netlink.c: In function ‘validate_set’:
>     net/openvswitch/flow_netlink.c:2711:29: warning: statement will never be executed [-Wswitch-unreachable]
>      2711 |  const struct ovs_key_ipv4 *ipv4_key;
>           |                             ^~~~~~~~
>
>     [1] https://bugs.llvm.org/show_bug.cgi?id=44916
>
>     Signed-off-by: Kees Cook <keescook at chromium.org>
>     Signed-off-by: David S. Miller <davem at davemloft.net>
>
> Cc: Kees Cook <keescook at chromium.org>
> Signed-off-by: Greg Rose <gvrose8192 at gmail.com>
> ---
Acked-by: Yi-Hung Wei <yihung.wei at gmail.com>