Re: [Qemu-devel] [PATCH 1/2] fix GCC 5.0.0 logical-not-parentheses warnings

[Paolo Bonzini <pbonzini@redhat.com>]

On 20/02/2015 15:18, Radim Krčmář wrote:
> man gcc:
>   Warn about logical not used on the left hand side operand of a
>   comparison.  This option does not warn if the RHS operand is of a
>   boolean type.
> 
> By preferring bool over int where sensible, but without modifying any
> depending code, make GCC happy in cases like this,
>   qemu-img.c: In function ‘compare_sectors’:
>   qemu-img.c:992:39: error: logical not is only applied to the left hand
>   side of comparison [-Werror=logical-not-parentheses]
>            if (!!memcmp(buf1, buf2, 512) != res) {
> 
> hw/ide/core.c:1836 doesn't throw an error,
>   assert(!!s->error == !!(s->status & ERR_STAT));
> even thought the second operand is int (and first hunk of this patch has
> a very similar case), maybe GCC developers still have a little faith in
> C programmers.
> 
> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
> ---
>  hw/net/virtio-net.c | 2 +-
>  kvm-all.c           | 2 +-
>  qemu-img.c          | 3 ++-
>  3 files changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index 45da34ad6129..ee234c963b6e 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -120,7 +120,7 @@ static void virtio_net_vhost_status(VirtIONet *n, uint8_t status)
>          return;
>      }
>  
> -    if (!!n->vhost_started ==
> +    if ((!!n->vhost_started) ==
>          (virtio_net_started(n, status) && !nc->peer->link_down)) {

Does it still break if you just swap the terms?

Paolo

>          return;
>      }
> diff --git a/kvm-all.c b/kvm-all.c
> index 05a79c20e0bb..07ef62cb3227 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -366,7 +366,7 @@ static void kvm_log_stop(MemoryListener *listener,
>      }
>  }
>  
> -static int kvm_set_migration_log(int enable)
> +static int kvm_set_migration_log(bool enable)
>  {
>      KVMState *s = kvm_state;
>      KVMSlot *mem;
> diff --git a/qemu-img.c b/qemu-img.c
> index e148af8a3e64..21fff2ad53d5 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -977,7 +977,8 @@ static int is_allocated_sectors_min(const uint8_t *buf, int n, int *pnum,
>  static int compare_sectors(const uint8_t *buf1, const uint8_t *buf2, int n,
>      int *pnum)
>  {
> -    int res, i;
> +    bool res;
> +    int i;
>  
>      if (n <= 0) {
>          *pnum = 0;
>