[Qemu-devel] [PATCH v2 05/23] error: Improve documentation around error_append_hint()

[Markus Armbruster <armbru@redhat.com>]

While there, tighten its assertion.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 include/qapi/error.h | 19 +++++++++++++++++--
 util/error.c         |  2 +-
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/include/qapi/error.h b/include/qapi/error.h
index b2362a5..048d947 100644
--- a/include/qapi/error.h
+++ b/include/qapi/error.h
@@ -18,6 +18,15 @@
  * Create an error:
  *     error_setg(&err, "situation normal, all fouled up");
  *
+ * Create an error and add additional explanation:
+ *     error_setg(&err, "invalid quark");
+ *     error_append_hint(&err, "Valid quarks are up, down, strange, "
+ *                       "charm, top, bottom\n");
+ *
+ * Do *not* contract this to
+ *     error_setg(&err, "invalid quark\n"
+ *                "Valid quarks are up, down, strange, charm, top, bottom");
+ *
  * Report an error to stderr:
  *     error_report_err(err);
  * This frees the error object.
@@ -26,6 +35,7 @@
  *     const char *msg = error_get_pretty(err);
  *     do with msg what needs to be done...
  *     error_free(err);
+ * Note that this loses hints added with error_append_hint().
  *
  * Handle an error without reporting it (just for completeness):
  *     error_free(err);
@@ -128,6 +138,7 @@ ErrorClass error_get_class(const Error *err);
  * If @errp is anything else, *@errp must be NULL.
  * The new error's class is ERROR_CLASS_GENERIC_ERROR, and its
  * human-readable error message is made from printf-style @fmt, ...
+ * The resulting message should not contain newlines.
  */
 #define error_setg(errp, fmt, ...)                              \
     error_setg_internal((errp), __FILE__, __LINE__, __func__,   \
@@ -184,7 +195,11 @@ void error_propagate(Error **dst_errp, Error *local_err);
 
 /**
  * Append a printf-style human-readable explanation to an existing error.
- * May be called multiple times, and safe if @errp is NULL.
+ * @errp may be NULL, but neither &error_fatal nor &error_abort.
+ * Trivially the case if you call it only after error_setg() or
+ * error_propagate().
+ * May be called multiple times.  The resulting hint should end with a
+ * newline.
  */
 void error_append_hint(Error **errp, const char *fmt, ...)
     GCC_FMT_ATTR(2, 3);
@@ -218,7 +233,7 @@ void error_free_or_abort(Error **errp);
 /*
  * Convenience function to error_report() and free @err.
  */
-void error_report_err(Error *);
+void error_report_err(Error *err);
 
 /*
  * Just like error_setg(), except you get to specify the error class.
diff --git a/util/error.c b/util/error.c
index 9b27c45..ebfb74b 100644
--- a/util/error.c
+++ b/util/error.c
@@ -132,7 +132,7 @@ void error_append_hint(Error **errp, const char *fmt, ...)
         return;
     }
     err = *errp;
-    assert(err && errp != &error_abort);
+    assert(err && errp != &error_abort && errp != &error_fatal);
 
     if (!err->hint) {
         err->hint = g_string_new(NULL);
-- 
2.4.3