Re: [PATCH v2] usb: gadget: net2280: Distribute switch variables for initialization

[Alan Stern]

On Thu, 20 Feb 2020, Kees Cook wrote:

> 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.
> 
> drivers/usb/gadget/udc/net2280.c: In function âhandle_stat0_irqs_superspeedâ:
> drivers/usb/gadget/udc/net2280.c:2871:22: warning: statement will never be executed [-Wswitch-unreachable]
>  2871 |   struct net2280_ep *e;
>       |                      ^
> 
> [1] https://bugs.llvm.org/show_bug.cgi?id=44916
> 
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
> v2: put everything in function body (Alan Stern)
> v1: https://lore.kernel.org/lkml/20200220062315.69253-1-keescook@xxxxxxxxxxxx

You might want to remove part of the last sentence in the patch
description.  Aside from that,

Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>

Alan Stern