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[Qemu-devel] [PATCH v3 09/24] error: New error_prepend(), error_reportf_
From: |
Markus Armbruster |
Subject: |
[Qemu-devel] [PATCH v3 09/24] error: New error_prepend(), error_reportf_err() |
Date: |
Fri, 18 Dec 2015 16:35:12 +0100 |
Instead of simply propagating an error verbatim, we sometimes want to
add to its message, like this:
frobnicate(arg, &err);
error_setg(errp, "Can't frobnicate %s: %s",
arg, error_get_pretty(err));
error_free(err);
This is suboptimal, because it loses err's hint (if any). Moreover,
when errp is &error_abort or is subsequently propagated to
&error_abort, the abort message points to the place where we last
added to the error, not to the place where it originated.
To avoid these issues, provide means to add to an error's message in
place:
frobnicate(arg, errp);
error_prepend(errp, "Can't frobnicate %s: ", arg);
Likewise, reporting an error like
frobnicate(arg, &err);
error_report("Can't frobnicate %s: %s", arg, error_get_pretty(err));
can lose err's hint. To avoid:
error_reportf_err(err, "Can't frobnicate %s: ", arg);
The next commits will put these functions to use.
Signed-off-by: Markus Armbruster <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
---
include/qapi/error.h | 31 +++++++++++++++++++++++++++++--
util/error.c | 33 +++++++++++++++++++++++++++++++++
2 files changed, 62 insertions(+), 2 deletions(-)
diff --git a/include/qapi/error.h b/include/qapi/error.h
index b18a608..45d6c72 100644
--- a/include/qapi/error.h
+++ b/include/qapi/error.h
@@ -31,6 +31,9 @@
* error_report_err(err);
* This frees the error object.
*
+ * Report an error to stderr with additional text prepended:
+ * error_reportf_err(err, "Could not frobnicate '%s': ", name);
+ *
* Report an error somewhere else:
* const char *msg = error_get_pretty(err);
* do with msg what needs to be done...
@@ -48,6 +51,10 @@
* error_propagate(errp, err);
* where Error **errp is a parameter, by convention the last one.
*
+ * Pass an existing error to the caller with the message modified:
+ * error_propagate(errp, err);
+ * error_prepend(errp, "Could not frobnicate '%s': ", name);
+ *
* Create a new error and pass it to the caller:
* error_setg(errp, "situation normal, all fouled up");
*
@@ -108,9 +115,10 @@
#ifndef ERROR_H
#define ERROR_H
+#include <stdarg.h>
+#include <stdbool.h>
#include "qemu/compiler.h"
#include "qapi-types.h"
-#include <stdbool.h>
/*
* Opaque error object.
@@ -208,7 +216,20 @@ void error_setg_win32_internal(Error **errp,
*/
void error_propagate(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);
+
+/*
+ * 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, ...)
+ GCC_FMT_ATTR(2, 3);
+
+/*
* Append a printf-style human-readable explanation to an existing error.
* @errp may be NULL, but not &error_fatal or &error_abort.
* Trivially the case if you call it only after error_setg() or
@@ -251,6 +272,12 @@ void error_free_or_abort(Error **errp);
void error_report_err(Error *err);
/*
+ * Convenience function to error_prepend(), error_report() and free @err.
+ */
+void error_reportf_err(Error *err, const char *fmt, ...)
+ GCC_FMT_ATTR(2, 3);
+
+/*
* Just like error_setg(), except you get to specify the error class.
* Note: use of error classes other than ERROR_CLASS_GENERIC_ERROR is
* strongly discouraged.
diff --git a/util/error.c b/util/error.c
index ebfb74b..57303fd 100644
--- a/util/error.c
+++ b/util/error.c
@@ -122,6 +122,29 @@ void error_setg_file_open_internal(Error **errp,
"Could not open '%s'", filename);
}
+void error_vprepend(Error **errp, const char *fmt, va_list ap)
+{
+ GString *newmsg;
+
+ if (!errp) {
+ return;
+ }
+
+ newmsg = g_string_new(NULL);
+ g_string_vprintf(newmsg, fmt, ap);
+ g_string_append(newmsg, (*errp)->msg);
+ (*errp)->msg = g_string_free(newmsg, 0);
+}
+
+void error_prepend(Error **errp, const char *fmt, ...)
+{
+ va_list ap;
+
+ va_start(ap, fmt);
+ error_vprepend(errp, fmt, ap);
+ va_end(ap);
+}
+
void error_append_hint(Error **errp, const char *fmt, ...)
{
va_list ap;
@@ -209,6 +232,16 @@ void error_report_err(Error *err)
error_free(err);
}
+void error_reportf_err(Error *err, const char *fmt, ...)
+{
+ va_list ap;
+
+ va_start(ap, fmt);
+ error_vprepend(&err, fmt, ap);
+ va_end(ap);
+ error_report_err(err);
+}
+
void error_free(Error *err)
{
if (err) {
--
2.4.3
- [Qemu-devel] [PATCH v3 19/24] pci-assign: Clean up "Failed to assign" error messages, (continued)
- [Qemu-devel] [PATCH v3 19/24] pci-assign: Clean up "Failed to assign" error messages, Markus Armbruster, 2015/12/18
- [Qemu-devel] [PATCH v3 13/24] spapr: Use error_reportf_err(), Markus Armbruster, 2015/12/18
- [Qemu-devel] [PATCH v3 17/24] vmdk: Clean up control flow in vmdk_parse_extents() a bit, Markus Armbruster, 2015/12/18
- [Qemu-devel] [PATCH v3 15/24] qemu-io qemu-nbd: Use error_report() etc. instead of fprintf(), Markus Armbruster, 2015/12/18
- [Qemu-devel] [PATCH v3 02/24] error: Use error_report_err() where appropriate (again), Markus Armbruster, 2015/12/18
- [Qemu-devel] [PATCH v3 12/24] error: Use error_prepend() where it makes obvious sense, Markus Armbruster, 2015/12/18
- [Qemu-devel] [PATCH v3 08/24] test-throttle: Simplify qemu_init_main_loop() error handling, Markus Armbruster, 2015/12/18
- [Qemu-devel] [PATCH v3 07/24] qemu-nbd: Clean up "Failed to load snapshot" error message, Markus Armbruster, 2015/12/18
- [Qemu-devel] [PATCH v3 04/24] error: Use error_report_err() instead of ad hoc prints, Markus Armbruster, 2015/12/18
- [Qemu-devel] [PATCH v3 01/24] qemu-nbd: Replace BSDism <err.h> by error_report(), Markus Armbruster, 2015/12/18
- [Qemu-devel] [PATCH v3 09/24] error: New error_prepend(), error_reportf_err(),
Markus Armbruster <=
- [Qemu-devel] [PATCH v3 10/24] error: Don't decorate original error message when adding to it, Markus Armbruster, 2015/12/18
- [Qemu-devel] [PATCH v3 06/24] block: Clean up "Could not create temporary overlay" error message, Markus Armbruster, 2015/12/18
- [Qemu-devel] [PATCH v3 03/24] error: Use error_report_err() instead of monitor_printf(), Markus Armbruster, 2015/12/18
- [Qemu-devel] [PATCH v3 16/24] error: Strip trailing '\n' from error string arguments (again), Markus Armbruster, 2015/12/18
- [Qemu-devel] [PATCH v3 14/24] migration: Use error_reportf_err() instead of monitor_printf(), Markus Armbruster, 2015/12/18
- [Qemu-devel] [PATCH v3 22/24] hw/s390x: Rename local variables Error *l_err to just err, Markus Armbruster, 2015/12/18
- [Qemu-devel] [PATCH v3 05/24] error: Improve documentation, Markus Armbruster, 2015/12/18
- [Qemu-devel] [PATCH v3 24/24] error: Consistently name Error * objects err, and not errp, Markus Armbruster, 2015/12/18