Re: [PATCH v2] Do not use %m in common code to print error messages

[Paolo Bonzini <pbonzini@redhat.com>]

On 18/10/19 15:07, Thomas Huth wrote:
> The %m format specifier is an extension from glibc - and when compiling
> QEMU for NetBSD, the compiler correctly complains, e.g.:
> 
> /home/qemu/qemu-test.ELjfrQ/src/util/main-loop.c: In function 'sigfd_handler':
> /home/qemu/qemu-test.ELjfrQ/src/util/main-loop.c:64:13: warning: %m is only
>  allowed in syslog(3) like functions [-Wformat=]
>              printf("read from sigfd returned %zd: %m\n", len);
>              ^
> Let's use g_strerror() here instead, which is an easy-to-use wrapper
> around the thread-safe strerror_r() function.
> 
> While we're at it, also convert the "printf()" in main-loop.c into
> the preferred "error_report()".
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  v2: Do not try to g_free() the strings
> 
>  hw/misc/tmp421.c | 4 ++--
>  util/main-loop.c | 3 ++-
>  util/systemd.c   | 4 ++--
>  3 files changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/misc/tmp421.c b/hw/misc/tmp421.c
> index 9f044705fa..c0bc150bca 100644
> --- a/hw/misc/tmp421.c
> +++ b/hw/misc/tmp421.c
> @@ -120,7 +120,7 @@ static void tmp421_get_temperature(Object *obj, Visitor *v, const char *name,
>      int tempid;
>  
>      if (sscanf(name, "temperature%d", &tempid) != 1) {
> -        error_setg(errp, "error reading %s: %m", name);
> +        error_setg(errp, "error reading %s: %s", name, g_strerror(errno));
>          return;
>      }
>  
> @@ -160,7 +160,7 @@ static void tmp421_set_temperature(Object *obj, Visitor *v, const char *name,
>      }
>  
>      if (sscanf(name, "temperature%d", &tempid) != 1) {
> -        error_setg(errp, "error reading %s: %m", name);
> +        error_setg(errp, "error reading %s: %s", name, g_strerror(errno));
>          return;
>      }
>  
> diff --git a/util/main-loop.c b/util/main-loop.c
> index e3eaa55866..eda63fe4e0 100644
> --- a/util/main-loop.c
> +++ b/util/main-loop.c
> @@ -61,7 +61,8 @@ static void sigfd_handler(void *opaque)
>          }
>  
>          if (len != sizeof(info)) {
> -            printf("read from sigfd returned %zd: %m\n", len);
> +            error_report("read from sigfd returned %zd: %s", len,
> +                         g_strerror(errno));
>              return;
>          }
>  
> diff --git a/util/systemd.c b/util/systemd.c
> index d22e86c707..1dd0367d9a 100644
> --- a/util/systemd.c
> +++ b/util/systemd.c
> @@ -60,8 +60,8 @@ unsigned int check_socket_activation(void)
>               * and we should exit.
>               */
>              error_report("Socket activation failed: "
> -                         "invalid file descriptor fd = %d: %m",
> -                         fd);
> +                         "invalid file descriptor fd = %d: %s",
> +                         fd, g_strerror(errno));
>              exit(EXIT_FAILURE);
>          }
>      }
> 

Queued, thanks.

Paolo