error: Fix examples in error.h's big comment

Mark a bad example more clearly.  Fix the error_propagate_prepend()
example.  Add a missing declaration and a second error pileup example.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Message-Id: <20200707160613.848843-2-armbru@redhat.com>
This commit is contained in:
Markus Armbruster 2020-07-07 18:05:29 +02:00
parent b6d7e9b66f
commit 47ff5ac81e

View File

@ -24,7 +24,7 @@
* "charm, top, bottom.\n");
*
* Do *not* contract this to
* error_setg(&err, "invalid quark\n"
* error_setg(&err, "invalid quark\n" // WRONG!
* "Valid quarks are up, down, strange, charm, top, bottom.");
*
* Report an error to the current monitor if we have one, else stderr:
@ -52,7 +52,8 @@
* where Error **errp is a parameter, by convention the last one.
*
* Pass an existing error to the caller with the message modified:
* error_propagate_prepend(errp, err);
* error_propagate_prepend(errp, err,
* "Could not frobnicate '%s': ", name);
*
* Avoid
* error_propagate(errp, err);
@ -108,12 +109,23 @@
* }
*
* Do *not* "optimize" this to
* Error *err = NULL;
* foo(arg, &err);
* bar(arg, &err); // WRONG!
* if (err) {
* handle the error...
* }
* because this may pass a non-null err to bar().
*
* Likewise, do *not*
* Error *err = NULL;
* if (cond1) {
* error_setg(&err, ...);
* }
* if (cond2) {
* error_setg(&err, ...); // WRONG!
* }
* because this may pass a non-null err to error_setg().
*/
#ifndef ERROR_H