From mboxrd@z Thu Jan  1 00:00:00 1970
From: Wen Congyang <wency@cn.fujitsu.com>
Subject: Re: [RFC Patch v4 7/9] correct xc_domain_save()'s
 return value
Date: Mon, 22 Sep 2014 16:41:15 +0800
Message-ID: <541FE0AB.1050808@cn.fujitsu.com>
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To: Olaf Hering <olaf@aepfle.de>
Cc: Ian Campbell <Ian.Campbell@citrix.com>, Ian Jackson <Ian.Jackson@eu.citrix.com>, Jiang Yunhong <yunhong.jiang@intel.com>, Dong Eddie <eddie.dong@intel.com>, xen devel <xen-devel@lists.xen.org>, Yang Hongyang <yanghy@cn.fujitsu.com>, Lai Jiangshan <laijs@cn.fujitsu.com>
List-Id: xen-devel@lists.xenproject.org

On 09/22/2014 04:13 PM, Olaf Hering wrote:
> On Mon, Sep 22, Wen Congyang wrote:
> 
>> The callbacks may be implemented in libxl, which is another process.
>> xc_domain_save() is a public API, and the caller may forget to set
>> the errno...
>>
>> So we cannot assume that the callbacks has set the errno
> 
> Then the caller is using xc_domain_save incorrectly.
> Looks like there is no API documentation, other than the source code.

What about correcting the errno before xc_domain_save() returns:
diff --git a/tools/libxc/xc_domain_save.c b/tools/libxc/xc_domain_save.c
index 6e14112..de8974a 100644
--- a/tools/libxc/xc_domain_save.c
+++ b/tools/libxc/xc_domain_save.c
@@ -2188,10 +2188,14 @@ int xc_domain_save(xc_interface *xch, int io_fd, uint32_t dom, uint32_t max_iter
     outbuf_free(&ob_pagebuf);
 
     errno = rc;
+    rc = !!errno;
+    if (errno == -1)
+        /* We cannot get the correct errno */
+        errno = 0;
 exit:
     DPRINTF("Save exit of domid %u with errno=%d\n", dom, errno);
 
-    return !!errno;
+    return rc;
 }
 
 /*


> 
> Olaf
> .
>