Re: [Qemu-devel] [PATCH] target-ppc: fix warn_unused_result build break with in-kernel HTAB support

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

Greg Kurz <gkurz@linux.vnet.ibm.com> writes:

> The 7029677e4 commit introduced the following build break:
>
> target-ppc/kvm.c: In function ‘kvmppc_hash64_write_pte’:
> target-ppc/kvm.c:2017:10: error: ignoring return value of ‘write’, declared
> with attribute warn_unused_result [-Werror=unused-result]
>      write(htab_fd, &hpte_buf, sizeof(hpte_buf));
>           ^
>
> Even though nothing is done for the moment if kvm_htab_write() fails, we
> obviously need to be explicit. Let's add an *empty* return path to please
> gcc.
>

Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

> Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
> ---
>  target-ppc/kvm.c |   10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
> index 2eaf956..343376c 100644
> --- a/target-ppc/kvm.c
> +++ b/target-ppc/kvm.c
> @@ -2012,9 +2012,15 @@ void kvmppc_hash64_write_pte(CPUPPCState *env, target_ulong pte_index,
>      hpte_buf.hpte[0] = pte0;
>      hpte_buf.hpte[1] = pte1;
>      /*
> -     * Write the hpte entry
> +     * Write the hpte entry.
> +     * CAUTION: write() has the warn_unused_result attribute. Hence we
> +     * need to check the return value, even though we do nothing.
>       */
> -    write(htab_fd, &hpte_buf, sizeof(hpte_buf));
> +    if (write(htab_fd, &hpte_buf, sizeof(hpte_buf)) < 0) {
> +        goto out_close;
> +    }
> +
> +out_close:
>      close(htab_fd);
>      return;
>