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[PULL,01/41] error: Document how to accumulate multiple errors

Message ID 1452699819-26608-2-git-send-email-armbru@redhat.com
State New
Headers show

Commit Message

Markus Armbruster Jan. 13, 2016, 3:42 p.m. UTC 
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>
---
 include/qapi/error.h | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
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Patch

diff --git a/include/qapi/error.h b/include/qapi/error.h
index 6285cf5..1480f59 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