Re: [Qemu-devel] [PATCH 4/5] Avoid unportable %m format

[Anthony Liguori <anthony@codemonkey.ws>]

On 07/08/2012 06:51 AM, blauwirbel@gmail.com wrote:
> From: Blue Swirl<blauwirbel@gmail.com>
>
> Replace %m format with explicit call to standard strerror().
>
> Signed-off-by: Blue Swirl<blauwirbel@gmail.com>

I would expect '%m' to be thread safe whereas strerror() isn't.  I don't think 
this change is actually good.

You'd need to do something more clever with strerror_r() to be equivalent.

Regards,

Anthony Liguori

> ---
>   kvm-all.c       |    3 ++-
>   main-loop.c     |    2 +-
>   net/tap-linux.c |    8 +++++---
>   qemu-nbd.c      |    3 +--
>   4 files changed, 9 insertions(+), 7 deletions(-)
>
> diff --git a/kvm-all.c b/kvm-all.c
> index f8e4328..d6f4819 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -1219,7 +1219,8 @@ int kvm_init(void)
>       s->vmfd = -1;
>       s->fd = qemu_open("/dev/kvm", O_RDWR);
>       if (s->fd == -1) {
> -        fprintf(stderr, "Could not access KVM kernel module: %m\n");
> +        fprintf(stderr, "Could not access KVM kernel module: %s\n",
> +                strerror(errno));
>           ret = -errno;
>           goto err;
>       }
> diff --git a/main-loop.c b/main-loop.c
> index eb3b6e6..472c55e 100644
> --- a/main-loop.c
> +++ b/main-loop.c
> @@ -116,7 +116,7 @@ static void sigfd_handler(void *opaque)
>           }
>
>           if (len != sizeof(info)) {
> -            printf("read from sigfd returned %zd: %m\n", len);
> +            printf("read from sigfd returned %zd: %s\n", len, strerror(errno));
>               return;
>           }
>
> diff --git a/net/tap-linux.c b/net/tap-linux.c
> index 41d581b..94e5b1e 100644
> --- a/net/tap-linux.c
> +++ b/net/tap-linux.c
> @@ -42,7 +42,7 @@ int tap_open(char *ifname, int ifname_size, int *vnet_hdr, int vnet_hdr_required
>
>       TFR(fd = open(PATH_NET_TUN, O_RDWR));
>       if (fd<  0) {
> -        error_report("could not open %s: %m", PATH_NET_TUN);
> +        error_report("could not open %s: %s", PATH_NET_TUN, strerror(errno));
>           return -1;
>       }
>       memset(&ifr, 0, sizeof(ifr));
> @@ -74,9 +74,11 @@ int tap_open(char *ifname, int ifname_size, int *vnet_hdr, int vnet_hdr_required
>       ret = ioctl(fd, TUNSETIFF, (void *)&ifr);
>       if (ret != 0) {
>           if (ifname[0] != '\0') {
> -            error_report("could not configure %s (%s): %m", PATH_NET_TUN, ifr.ifr_name);
> +            error_report("could not configure %s (%s): %s", PATH_NET_TUN,
> +                         ifr.ifr_name, strerror(errno));
>           } else {
> -            error_report("could not configure %s: %m", PATH_NET_TUN);
> +            error_report("could not configure %s: %s", PATH_NET_TUN,
> +                         strerror(errno));
>           }
>           close(fd);
>           return -1;
> diff --git a/qemu-nbd.c b/qemu-nbd.c
> index 5a0300e..099b5ed 100644
> --- a/qemu-nbd.c
> +++ b/qemu-nbd.c
> @@ -213,8 +213,7 @@ static void *nbd_client_thread(void *arg)
>
>       fd = open(device, O_RDWR);
>       if (fd<  0) {
> -        /* Linux-only, we can use %m in printf.  */
> -        fprintf(stderr, "Failed to open %s: %m", device);
> +        fprintf(stderr, "Failed to open %s: %s", device, strerror(errno));
>           goto out;
>       }
>