Re: [Qemu-devel] [PATCH V8 3/8] util: add error_append()

[Peter Crosthwaite]

On Fri, Jan 3, 2014 at 1:08 PM, Wenchao Xia <address@hidden> wrote:
> Signed-off-by: Wenchao Xia <address@hidden>
> ---
>  include/qapi/error.h |    6 ++++++
>  util/error.c         |   21 +++++++++++++++++++++
>  2 files changed, 27 insertions(+), 0 deletions(-)
>
> diff --git a/include/qapi/error.h b/include/qapi/error.h
> index 7d4c696..bcfb724 100644
> --- a/include/qapi/error.h
> +++ b/include/qapi/error.h
> @@ -30,6 +30,12 @@ typedef struct Error Error;
>  void error_set(Error **err, ErrorClass err_class, const char *fmt, ...) 
> GCC_FMT_ATTR(3, 4);
>
>  /**
> + * Append message to err if err != NULL && *err != NULL. "\n" will be 
> inserted
> + * after old message.
> + */
> +void error_append(Error **err, const char *fmt, ...) GCC_FMT_ATTR(2, 3);
> +
> +/**
>   * Set an indirect pointer to an error given a ErrorClass value and a
>   * printf-style human message, followed by a strerror() string if
>   * @os_error is not zero.
> diff --git a/util/error.c b/util/error.c
> index 3ee362a..64bbb2d 100644
> --- a/util/error.c
> +++ b/util/error.c
> @@ -46,6 +46,27 @@ void error_set(Error **errp, ErrorClass err_class, const 
> char *fmt, ...)
>      errno = saved_errno;
>  }
>
> +void error_append(Error **err, const char *fmt, ...)

errp

> +{
> +    va_list ap;
> +    gchar *msg, *msg_old;
> +
> +    if (!err || !*err) {

Should appending to an unset error really be a nop? You should just
set the error as normal in this case (error_set()?).

This avoids callers having to:

if (error_is_set(&err)) {
   error_append(&err);
} else {
   error_set(&err);
}

so they can just append if they want appending.

Generally speaking, appending to nothing should give you something.

Regards,
Peter

> +        return;
> +    }
> +
> +    va_start(ap, fmt);
> +    msg = g_strdup_vprintf(fmt, ap);
> +    va_end(ap);
> +
> +    msg_old = (*err)->msg;
> +    (*err)->msg = g_strdup_printf("%s\n%s", msg_old, msg);
> +
> +    g_free(msg);
> +    g_free(msg_old);
> +
> +}
> +
>  void error_set_errno(Error **errp, int os_errno, ErrorClass err_class,
>                       const char *fmt, ...)
>  {
> --
> 1.7.1
>
>