From 1dd5b71d14b5c5360f97071041ec1bdd1f8d2445 Mon Sep 17 00:00:00 2001
From: Ben Pfaff <blp@nicira.com>
Date: Wed, 9 Mar 2011 12:41:37 -0800
Subject: [PATCH] ovsdb: Improve error reporting for some internal errors.

Sometimes internal errors are generated based on an originating error.  In
these cases we were just throwing this information away.  This commit adds
this information to the internal error report so that the error will be
easier to track down.

I haven't actually seen a situation like this come up.
---
 lib/ovsdb-error.c   | 20 ++++++++++++++++++--
 lib/ovsdb-error.h   | 22 ++++++++++++++++++----
 ovsdb/transaction.c |  8 +++-----
 3 files changed, 39 insertions(+), 11 deletions(-)

diff --git a/lib/ovsdb-error.c b/lib/ovsdb-error.c
index d6b4576ea..3b90b1616 100644
--- a/lib/ovsdb-error.c
+++ b/lib/ovsdb-error.c
@@ -1,4 +1,4 @@
-/* Copyright (c) 2009, 2010 Nicira Networks
+/* Copyright (c) 2009, 2010, 2011 Nicira Networks
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -114,8 +114,16 @@ ovsdb_wrap_error(struct ovsdb_error *error, const char *details, ...)
     return error;
 }
 
+/* Returns an ovsdb_error that represents an internal error for file name
+ * 'file' and line number 'line', with 'details' (formatted as with printf())
+ * as the associated message.  The caller is responsible for freeing the
+ * returned error.
+ *
+ * If 'inner_error' is nonnull then the returned error is wrapped around
+ * 'inner_error'.  Takes ownership of 'inner_error'.  */
 struct ovsdb_error *
-ovsdb_internal_error(const char *file, int line, const char *details, ...)
+ovsdb_internal_error(struct ovsdb_error *inner_error,
+                     const char *file, int line, const char *details, ...)
 {
     struct ds ds = DS_EMPTY_INITIALIZER;
     struct backtrace backtrace;
@@ -144,6 +152,14 @@ ovsdb_internal_error(const char *file, int line, const char *details, ...)
 
     ds_put_format(&ds, " (%s %s%s)", program_name, VERSION, BUILDNR);
 
+    if (inner_error) {
+        char *s = ovsdb_error_to_string(inner_error);
+        ds_put_format(&ds, " (generated from: %s)", s);
+        free(s);
+
+        ovsdb_error_destroy(inner_error);
+    }
+
     error = ovsdb_error("internal error", "%s", ds_cstr(&ds));
 
     ds_destroy(&ds);
diff --git a/lib/ovsdb-error.h b/lib/ovsdb-error.h
index 2bff3ae56..89b0c19b2 100644
--- a/lib/ovsdb-error.h
+++ b/lib/ovsdb-error.h
@@ -1,4 +1,4 @@
-/* Copyright (c) 2009, 2010 Nicira Networks
+/* Copyright (c) 2009, 2010, 2011 Nicira Networks
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -35,11 +35,25 @@ struct ovsdb_error *ovsdb_wrap_error(struct ovsdb_error *error,
                                      const char *details, ...)
     PRINTF_FORMAT(2, 3);
 
-struct ovsdb_error *ovsdb_internal_error(const char *file, int line,
+struct ovsdb_error *ovsdb_internal_error(struct ovsdb_error *error,
+                                         const char *file, int line,
                                          const char *details, ...)
-    PRINTF_FORMAT(3, 4)
+    PRINTF_FORMAT(4, 5)
     WARN_UNUSED_RESULT;
-#define OVSDB_BUG(MSG) ovsdb_internal_error(__FILE__, __LINE__, "%s", MSG)
+
+/* Returns a pointer to an ovsdb_error that represents an internal error for
+ * the current file name and line number with MSG as the associated message.
+ * The caller is responsible for freeing the internal error. */
+#define OVSDB_BUG(MSG)                                      \
+    ovsdb_internal_error(NULL, __FILE__, __LINE__, "%s", MSG)
+
+/* Returns a pointer to an ovsdb_error that represents an internal error for
+ * the current file name and line number, with MSG as the associated message.
+ * If ERROR is nonnull then the internal error is wrapped around ERROR.  Takes
+ * ownership of ERROR.  The caller is responsible for freeing the returned
+ * error. */
+#define OVSDB_WRAP_BUG(MSG, ERROR)                          \
+    ovsdb_internal_error(ERROR, __FILE__, __LINE__, "%s", MSG)
 
 void ovsdb_error_destroy(struct ovsdb_error *);
 struct ovsdb_error *ovsdb_error_clone(const struct ovsdb_error *)
diff --git a/ovsdb/transaction.c b/ovsdb/transaction.c
index b26705a3a..b7c57e57e 100644
--- a/ovsdb/transaction.c
+++ b/ovsdb/transaction.c
@@ -1,4 +1,4 @@
-/* Copyright (c) 2009, 2010 Nicira Networks
+/* Copyright (c) 2009, 2010, 2011 Nicira Networks
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -218,8 +218,7 @@ update_row_ref_count(struct ovsdb_txn *txn, struct ovsdb_txn_row *r)
         if (r->old) {
             error = ovsdb_txn_adjust_row_refs(txn, r->old, column, -1);
             if (error) {
-                ovsdb_error_destroy(error);
-                return OVSDB_BUG("error decreasing refcount");
+                return OVSDB_WRAP_BUG("error decreasing refcount", error);
             }
         }
         if (r->new) {
@@ -476,8 +475,7 @@ ovsdb_txn_commit(struct ovsdb_txn *txn, bool durable)
      * was really a no-op. */
     error = for_each_txn_row(txn, determine_changes);
     if (error) {
-        ovsdb_error_destroy(error);
-        return OVSDB_BUG("can't happen");
+        return OVSDB_WRAP_BUG("can't happen", error);
     }
     if (list_is_empty(&txn->txn_tables)) {
         ovsdb_txn_abort(txn);
-- 
2.43.0