A tevent function to propagate error info up the stack

[Richard Sharpe]

Hi folks,

This is designed to allow us to propagate error locations up the stack
so that DEBUG messages can tell us where the error really came from.

Does this seem like a reasonable approach?

diff --git a/lib/tevent/tevent.h b/lib/tevent/tevent.h
index 6b4d371..296033a 100644
--- a/lib/tevent/tevent.h
+++ b/lib/tevent/tevent.h
@@ -1037,6 +1037,45 @@ bool _tevent_req_error(struct tevent_req *req,

 #ifdef DOXYGEN
 /**
+ * @brief An async request is passing on an error from below.
+ *
+ * This function is to be used by implementors of async requests. When a
+ * callback needs to pass an error back up to another callback, use this
+ * function with the appropriate status code and request to get the error
+ * location from.
+ *
+ * If error is 0 the function returns false and does nothing more.
+ *
+ * @param[in]  req      The request with an error.
+ *
+ * @param[in]  error    The error code.
+ *
+ * @param[in]  orig_req The request to take the error location from.
+ *
+ * @return              On success true is returned, false if error is 0.
+ *
+ * @code
+ * ret = some_func(subreq, &sys_errno);
+ * if (ret == -1) {
+ *     tevent_req_error_propogate(req, sys_errno, subreq);
+ *     return;
+ * }
+ * @endcode
+ */
+bool tevent_req_error_propogate(struct tevent_req *req,
+                               uint64_t error,
+                               struct tevent_req *subreq);
+#else
+bool _tevent_req_error_propogate(struct tevent_req *req,
+                                uint64_t error,
+                                struct tevent_req *subreq,
+                                const char *location);
+#define tevent_req_error_propogate(req, error) \
+       _tevent_req_error_propogate(req, error, subreq, __location__)
+#endif
+
+#ifdef DOXYGEN
+/**
  * @brief Helper function for nomem check.
  *
  * Convenience helper to easily check alloc failure within a callback


-- 
Regards,
Richard Sharpe
(何以解憂？唯有杜康。--曹操)