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Re: [Qemu-ppc] [PATCH 7/9] openpic: avoid a warning from clang analyzer

From: Scott Wood
Subject: Re: [Qemu-ppc] [PATCH 7/9] openpic: avoid a warning from clang analyzer
Date: Mon, 12 Sep 2011 12:12:30 -0500
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20110428 Fedora/3.1.10-1.fc15 Thunderbird/3.1.10

On 09/04/2011 10:52 AM, Blue Swirl wrote:
> Avoid this warning by clang analyzer by defining a default case:
> /src/qemu/hw/openpic.c:477:5: warning: Undefined or garbage value
> returned to caller
>     return retval;
> Signed-off-by: Blue Swirl <address@hidden>
> ---
>  hw/openpic.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> diff --git a/hw/openpic.c b/hw/openpic.c
> index 26c96e2..4b883ac 100644
> --- a/hw/openpic.c
> +++ b/hw/openpic.c
> @@ -469,6 +469,7 @@ static inline uint32_t read_IRQreg (openpic_t
> *opp, int n_IRQ, uint32_t reg)
>      case IRQ_IPVP:
>          retval = opp->src[n_IRQ].ipvp;
>          break;
> +    default:
>      case IRQ_IDE:
>          retval = opp->src[n_IRQ].ide;
>          break;

What's special about IDE?  Shouldn't it return 0xffffffff as some other
functions (e.g. openpic_gbl_read) do with unrecognized registers?  Then
there's openpic_src_read() which has still different behavior for the
same registers. :-P

Note that this function is only ever called with a constant in "reg".
Since it's a static function and all call sites could have been
verified, this could be considered a flaw in clang's analyzer.  This
workaround will prevent GCC from issuing a warning if a new caller is
added that passes a different constant value.

The best answer is probably to just get rid of this function and have
the caller refer to opp->src[n_irq].whatever directly.  write_IRQreg()
could be split into something like set_src_ipvp() and set_src_ide().


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