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Date: Fri, 4 Jan 2013 15:55:42 +0100
From: Stefan Hajnoczi <stefanha@gmail.com>
Message-ID: <20130104145542.GB6310@stefanha-thinkpad.hitronhub.home>
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Subject: Re: [Qemu-devel] [PATCH 2/6] snapshot: add error set function
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To: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
Cc: kwolf@redhat.com, pbonzini@redhat.com, aliguori@us.ibm.com, qemu-devel@nongnu.org, blauwirbel@gmail.com

On Mon, Dec 17, 2012 at 02:25:05PM +0800, Wenchao Xia wrote:

This patch has nothing to do with snapshots, so "snapshot: add error set
function" is not a useful commit message.  "error: add
error_set_replace()" would be okay.  Please use git log <filename> on
the file you are modifying to find good component names (e.g. "block:",
"error:").

> @@ -29,6 +29,9 @@ typedef struct Error Error;
>   */
>  void error_set(Error **err, ErrorClass err_class, const char *fmt, ...) GCC_FMT_ATTR(3, 4);
>  
> +void error_set_replace(Error **err, ErrorClass err_class, const char *fmt, ...)
> +GCC_FMT_ATTR(3, 4);
> +
>  /**
>   * Set an indirect pointer to an error given a ErrorClass value and a
>   * printf-style human message, followed by a strerror() string if
> @@ -43,6 +46,12 @@ void error_set_errno(Error **err, int os_error, ErrorClass err_class, const char
>      error_set(err, ERROR_CLASS_GENERIC_ERROR, fmt, ## __VA_ARGS__)
>  #define error_setg_errno(err, os_error, fmt, ...) \
>      error_set_errno(err, os_error, ERROR_CLASS_GENERIC_ERROR, fmt, ## __VA_ARGS__)
> +#define error_setg_replace(err, fmt, ...) do {                     \
> +    if (*err != NULL) { \
> +        error_free(*err); \
> +     } \
> +    error_set(err, ERROR_CLASS_GENERIC_ERROR, fmt, ## __VA_ARGS__); \
> +} while (/*CONSTCOND*/0)

Why not use error_set_replace() to get rid of the error_free() check?

Stefan