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[Qemu-devel] [PULL 25/41] error: New error_prepend(), error_reportf_err(
From: |
Markus Armbruster |
Subject: |
[Qemu-devel] [PULL 25/41] error: New error_prepend(), error_reportf_err() |
Date: |
Wed, 13 Jan 2016 16:43:23 +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>
Message-Id: <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] [PULL 11/41] sysbus: Don't use hw_error() in machine_init_done_notifiers, (continued)
- [Qemu-devel] [PULL 11/41] sysbus: Don't use hw_error() in machine_init_done_notifiers, Markus Armbruster, 2016/01/13
- [Qemu-devel] [PULL 17/41] qemu-nbd: Replace BSDism <err.h> by error_report(), Markus Armbruster, 2016/01/13
- [Qemu-devel] [PULL 28/41] error: Use error_prepend() where it makes obvious sense, Markus Armbruster, 2016/01/13
- [Qemu-devel] [PULL 19/41] error: Use error_report_err() instead of monitor_printf(), Markus Armbruster, 2016/01/13
- [Qemu-devel] [PULL 35/41] pci-assign: Clean up "Failed to assign" error messages, Markus Armbruster, 2016/01/13
- [Qemu-devel] [PULL 06/41] arm_mptimer: Don't use hw_error() in realize() method, Markus Armbruster, 2016/01/13
- [Qemu-devel] [PULL 14/41] isa: Clean up inappropriate hw_error(), Markus Armbruster, 2016/01/13
- [Qemu-devel] [PULL 23/41] qemu-nbd: Clean up "Failed to load snapshot" error message, Markus Armbruster, 2016/01/13
- [Qemu-devel] [PULL 12/41] isa: Trivially convert remaining PCI-ISA bridges to realize(), Markus Armbruster, 2016/01/13
- [Qemu-devel] [PULL 16/41] xen-hvm: Mark inappropriate error handling FIXME, Markus Armbruster, 2016/01/13
- [Qemu-devel] [PULL 25/41] error: New error_prepend(), error_reportf_err(),
Markus Armbruster <=
- [Qemu-devel] [PULL 10/41] hw/arm/virt: Fix property "gic-version" error handling, Markus Armbruster, 2016/01/13
- [Qemu-devel] [PULL 29/41] spapr: Use error_reportf_err(), Markus Armbruster, 2016/01/13
- [Qemu-devel] [PULL 41/41] checkpatch: Detect newlines in error_report and other error functions, Markus Armbruster, 2016/01/13
- [Qemu-devel] [PULL 33/41] vmdk: Clean up control flow in vmdk_parse_extents() a bit, Markus Armbruster, 2016/01/13
- [Qemu-devel] [PULL 26/41] error: Don't decorate original error message when adding to it, Markus Armbruster, 2016/01/13
- [Qemu-devel] [PULL 32/41] error: Strip trailing '\n' from error string arguments (again), Markus Armbruster, 2016/01/13
- [Qemu-devel] [PULL 40/41] error: Consistently name Error * objects err, and not errp, Markus Armbruster, 2016/01/13
- [Qemu-devel] [PULL 22/41] block: Clean up "Could not create temporary overlay" error message, Markus Armbruster, 2016/01/13
- [Qemu-devel] [PULL 27/41] error: Use error_reportf_err() where it makes obvious sense, Markus Armbruster, 2016/01/13
- [Qemu-devel] [PULL 30/41] migration: Use error_reportf_err() instead of monitor_printf(), Markus Armbruster, 2016/01/13