Re: [Qemu-devel] [PATCH 1/4] os-posix/win32: convert fprintf/perror to error_report

[Eric Blake <eblake@redhat.com>]

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On 09/25/2014 03:46 AM, arei.gonglei@huawei.com wrote:
> From: Gonglei <arei.gonglei@huawei.com>
> 
> Signed-off-by: Gonglei <arei.gonglei@huawei.com>
> ---
>  os-posix.c | 34 ++++++++++++++++++----------------
>  os-win32.c |  3 ++-
>  2 files changed, 20 insertions(+), 17 deletions(-)
> 
> diff --git a/os-posix.c b/os-posix.c
> index cb2a7f7..9d5ae70 100644
> --- a/os-posix.c
> +++ b/os-posix.c
> @@ -39,6 +39,7 @@
>  #include "sysemu/sysemu.h"
>  #include "net/slirp.h"
>  #include "qemu-options.h"
> +#include "qemu/error-report.h"
>  
>  #ifdef CONFIG_LINUX
>  #include <sys/prctl.h>
> @@ -120,11 +121,11 @@ void os_set_proc_name(const char *s)
>      /* Could rewrite argv[0] too, but that's a bit more complicated.
>         This simple way is enough for `top'. */
>      if (prctl(PR_SET_NAME, name)) {
> -        perror("unable to change process name");
> +        error_report("unable to change process name");

This loses the value of errno that perror would have displayed.  Is that
reduction in error message quality intentional?  If not, then this is
not a trivial conversion; if it is, then your commit message should call
it out.

> @@ -167,20 +168,20 @@ static void change_process_uid(void)
>  {
>      if (user_pwd) {
>          if (setgid(user_pwd->pw_gid) < 0) {
> -            fprintf(stderr, "Failed to setgid(%d)\n", user_pwd->pw_gid);
> +            error_report("Failed to setgid(%d)\n", user_pwd->pw_gid);

No trailing \n for error_report, please. (You got it right in most of
your conversions)


> @@ -190,11 +191,11 @@ static void change_root(void)
>  {
>      if (chroot_dir) {
>          if (chroot(chroot_dir) < 0) {
> -            fprintf(stderr, "chroot failed\n");
> +            error_report("chroot failed");
>              exit(1);
>          }
>          if (chdir("/")) {
> -            perror("not able to chdir to /");
> +            error_report("not able to chdir to /");

Another loss of errno value from perror.

>              exit(1);
>          }
>      }
> @@ -224,7 +225,7 @@ void os_daemonize(void)
>              if (len != 1)
>                  exit(1);
>              else if (status == 1) {
> -                fprintf(stderr, "Could not acquire pidfile: %s\n", strerror(errno));
> +                error_report("Could not acquire pidfile: %s", strerror(errno));

This code is broken.  The earlier 'if (len != 1)' fails to print a
message before exiting (not to mention it violates coding style by
omitting {}).  Then, if we get inside the 'else if (status == 1)'
conditional, then we KNOW that read() succeeded, and therefore errno is
unspecified.  Printing strerror(errno) on a random value is NOT helpful.


> @@ -267,7 +268,7 @@ void os_setup_post(void)
>  	    exit(1);
>  
>          if (chdir("/")) {
> -            perror("not able to chdir to /");
> +            error_report("not able to chdir to /");

Another loss of errno reporting.

>              exit(1);
>          }
>  	TFR(fd = qemu_open("/dev/null", O_RDWR));
> @@ -292,10 +293,11 @@ void os_pidfile_error(void)
>      if (daemonize) {
>          uint8_t status = 1;
>          if (write(fds[1], &status, 1) != 1) {
> -            perror("daemonize. Writing to pipe\n");
> +            error_report("daemonize. Writing to pipe");

and another.

> @@ -338,7 +340,7 @@ int os_mlock(void)
>  
>      ret = mlockall(MCL_CURRENT | MCL_FUTURE);
>      if (ret < 0) {
> -        perror("mlockall");
> +        error_report("mlockall");

and another.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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