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authorMarkus Armbruster <armbru@redhat.com>2015-11-17 17:05:49 +0100
committerMarkus Armbruster <armbru@redhat.com>2016-01-13 11:58:57 +0100
commit8d780f43921feb7fd8d0b58f779a22d1265f2378 (patch)
tree0447d97a34dd5b11431680a8eaaf7979065f7d64 /include/qapi/error.h
parent649a1bbaf95adb228f1030ab0618a932bc26aa8b (diff)
downloadfocaccia-qemu-8d780f43921feb7fd8d0b58f779a22d1265f2378.tar.gz
focaccia-qemu-8d780f43921feb7fd8d0b58f779a22d1265f2378.zip
error: Document how to accumulate multiple errors
Suggested-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <1447776349-2344-1-git-send-email-armbru@redhat.com>
Diffstat (limited to 'include/qapi/error.h')
-rw-r--r--include/qapi/error.h17
1 files changed, 17 insertions, 0 deletions
diff --git a/include/qapi/error.h b/include/qapi/error.h
index 6285cf50d1..1480f59ec5 100644
--- a/include/qapi/error.h
+++ b/include/qapi/error.h
@@ -76,6 +76,23 @@
  * But when all you do with the error is pass it on, please use
  *     foo(arg, errp);
  * for readability.
+ *
+ * Receive and accumulate multiple errors (first one wins):
+ *     Error *err = NULL, *local_err = NULL;
+ *     foo(arg, &err);
+ *     bar(arg, &local_err);
+ *     error_propagate(&err, local_err);
+ *     if (err) {
+ *         handle the error...
+ *     }
+ *
+ * Do *not* "optimize" this to
+ *     foo(arg, &err);
+ *     bar(arg, &err); // WRONG!
+ *     if (err) {
+ *         handle the error...
+ *     }
+ * because this may pass a non-null err to bar().
  */
 
 #ifndef ERROR_H