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Re: [Qemu-devel] [PATCH] target-i386: fix clang sanitize warning
From: |
Peter Maydell |
Subject: |
Re: [Qemu-devel] [PATCH] target-i386: fix clang sanitize warning |
Date: |
Tue, 27 Oct 2015 16:02:33 +0000 |
On 27 October 2015 at 14:24, <address@hidden> wrote:
> From: Marc-André Lureau <address@hidden>
>
> When running vhost-user-test with clang compiled qemu with
> --extra-cflags=-fsanitize=undefined, the following error is printed:
>
> qemu/target-i386/translate.c:2435:26: runtime error: left shift of negative
> value -8
>
> According to c99, this is undefined behaviour. (see also
> http://stackoverflow.com/questions/22883790/left-shift-of-negative-values)
>
> I guess the intended code is to subtract (8 << s->dflag), thus adding
> parentheses seems to be enough.
>
> Signed-off-by: Marc-André Lureau <address@hidden>
> ---
> target-i386/translate.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/target-i386/translate.c b/target-i386/translate.c
> index 764b1e4..862f8e0 100644
> --- a/target-i386/translate.c
> +++ b/target-i386/translate.c
> @@ -2432,7 +2432,7 @@ static void gen_pusha(DisasContext *s)
> {
> int i;
> gen_op_movl_A0_reg(R_ESP);
> - gen_op_addl_A0_im(-8 << s->dflag);
> + gen_op_addl_A0_im(-(8 << s->dflag));
> if (!s->ss32)
> tcg_gen_ext16u_tl(cpu_A0, cpu_A0);
> tcg_gen_mov_tl(cpu_T[1], cpu_A0);
Looks like Eduardo already had a patch on list for this:
http://patchwork.ozlabs.org/patch/524590/
thanks
-- PMM