Re: [Qemu-devel] [PATCH 2/2] util/error: Remove unnecessary saved_errno

[Eric Blake <eblake@redhat.com>]

On 3/2/19 4:38 PM, Philippe Mathieu-Daudé wrote:
> Since 552375088a8, error_set_errno() calls error_setv() which
> already protect errno for clobbering.
> Remove the now unnecessary saved_errno.
> 
> Suggested-by: Thomas Huth <thuth@redhat.com>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
>  util/error.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/util/error.c b/util/error.c
> index 934a78e1b1..0402fa1b9d 100644
> --- a/util/error.c
> +++ b/util/error.c
> @@ -101,14 +101,11 @@ void error_setg_errno_internal(Error **errp,
>                                 int os_errno, const char *fmt, ...)
>  {
>      va_list ap;
> -    int saved_errno = errno;
>  
>      va_start(ap, fmt);
>      error_setv(errp, src, line, func, ERROR_CLASS_GENERIC_ERROR, fmt, ap,
>                 os_errno != 0 ? strerror(os_errno) : NULL);
>      va_end(ap);
> -
> -    errno = saved_errno;

NACK. strerror() can clobber errno, so you still need to restore
saved_errno, regardless of what error_setv() does internally.
-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org