error: make Error **errp const where it is appropriate

Mostly, Error ** is for returning error from the function, so the
callee sets it. However these three functions get already filled errp
parameter. They don't change the pointer itself, only change the
internal state of referenced Error object. So we can make it
Error *const * errp, to stress the behavior. It will also help
coccinelle script (in future) to distinguish such cases from common
errp usage.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20191205174635.18758-4-vsementsov@virtuozzo.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[Commit message typo fixed]
Signed-off-by: Markus Armbruster <armbru@redhat.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/include/qapi/error.h b/include/qapi/error.h
index 3f95141a01..ad5b6e896d 100644
--- a/include/qapi/error.h
+++ b/include/qapi/error.h
@@ -233,13 +233,13 @@ void error_propagate_prepend(Error **dst_errp, Error *local_err,
  * Prepend some text to @errp's human-readable error message.
  * The text is made by formatting @fmt, @ap like vprintf().
  */
-void error_vprepend(Error **errp, const char *fmt, va_list ap);
+void error_vprepend(Error *const *errp, const char *fmt, va_list ap);
 
 /*
  * Prepend some text to @errp's human-readable error message.
  * The text is made by formatting @fmt, ... like printf().
  */
-void error_prepend(Error **errp, const char *fmt, ...)
+void error_prepend(Error *const *errp, const char *fmt, ...)
     GCC_FMT_ATTR(2, 3);
 
 /*
@@ -256,7 +256,7 @@ void error_prepend(Error **errp, const char *fmt, ...)
  * May be called multiple times.  The resulting hint should end with a
  * newline.
  */
-void error_append_hint(Error **errp, const char *fmt, ...)
+void error_append_hint(Error *const *errp, const char *fmt, ...)
     GCC_FMT_ATTR(2, 3);
 
 /*