On Fri, 11 Mar 2011 15:00:41 -0600
Anthony Liguori <aligu...@us.ibm.com> wrote:
> The Error class is similar to QError (now deprecated) except that it supports
> propagation. This allows for higher quality error handling. It's losely
> modeled after glib style GErrors.
I think Daniel asked this, but I can't remember your answer: why don't we
use GError then?
Also, I think this patch needs more description regarding how this is going
to replace QError. I mean, we want to deprecate QError but it seems to me
that you're going to maintain the error declaration format, like:
"{ 'class': 'CommandNotFound', 'data': { 'name': %s } }"
And the current QError class list in qerror.h. Did I get it right?
More comments below.
> Signed-off-by: Anthony Liguori <aligu...@us.ibm.com>
>
> diff --git a/Makefile.objs b/Makefile.objs
> index 0ba02c7..da31530 100644
> --- a/Makefile.objs
> +++ b/Makefile.objs
> @@ -15,6 +15,7 @@ oslib-obj-$(CONFIG_POSIX) += oslib-posix.o
>
> block-obj-y = cutils.o cache-utils.o qemu-malloc.o qemu-option.o module.o
> block-obj-y += nbd.o block.o aio.o aes.o qemu-config.o
> +block-obj-y += error.o
> block-obj-$(CONFIG_POSIX) += posix-aio-compat.o
> block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
You also have to do this:
-CHECK_PROG_DEPS = qemu-malloc.o $(oslib-obj-y) $(trace-obj-y)
+CHECK_PROG_DEPS = qemu-malloc.o error.o qerror.o $(oslib-obj-y) $(trace-obj-y)
Otherwise you break check build.
> diff --git a/error.c b/error.c
> new file mode 100644
> index 0000000..5d84106
> --- /dev/null
> +++ b/error.c
> @@ -0,0 +1,122 @@
> +/*
> + * QEMU Error Objects
> + *
> + * Copyright IBM, Corp. 2011
> + *
> + * Authors:
> + * Anthony Liguori <aligu...@us.ibm.com>
> + *
> + * This work is licensed under the terms of the GNU LGPL, version 2. See
> + * the COPYING.LIB file in the top-level directory.
> + */
> +#include "error.h"
> +#include "error_int.h"
> +#include "qemu-objects.h"
> +#include "qerror.h"
> +#include <assert.h>
> +
> +struct Error
> +{
> + QDict *obj;
'obj' is a bit generic and sometimes it's used to denote QObjects in the
code, I suggest 'error_dict' or something that communicates its purpose.
> + const char *fmt;
> + char *msg;
I don't think we should store 'msg', more about this in error_get_pretty().
> +};
> +
> +void error_set(Error **errp, const char *fmt, ...)
> +{
> + Error *err;
> + va_list ap;
> +
> + if (errp == NULL) {
> + return;
> + }
> +
> + err = qemu_mallocz(sizeof(*err));
> +
> + va_start(ap, fmt);
> + err->obj = qobject_to_qdict(qobject_from_jsonv(fmt, &ap));
> + va_end(ap);
> + err->fmt = fmt;
> +
> + *errp = err;
> +}
> +
> +bool error_is_set(Error **errp)
> +{
> + return (errp && *errp);
> +}
> +
> +const char *error_get_pretty(Error *err)
> +{
> + if (err->msg == NULL) {
> + QString *str;
> + str = qerror_format(err->fmt, err->obj);
> + err->msg = qemu_strdup(qstring_get_str(str));
Four comments here:
1. This is missing a QDECREF(str);
2. Storing 'msg' looks like an unnecessary optimization to me, why don't
we just re-create it when error_get_pretty() is called?
3. This function is not used by this series
4. I think it's a good idea to assert on Error == NULL, specially
because some functions accept it
> + }
> +
> + return err->msg;
> +}
> +
> +const char *error_get_field(Error *err, const char *field)
> +{
> + if (strcmp(field, "class") == 0) {
> + return qdict_get_str(err->obj, field);
> + } else {
> + QDict *dict = qdict_get_qdict(err->obj, "data");
> + return qdict_get_str(dict, field);
> + }
> +}
> +
> +void error_free(Error *err)
> +{
> + QDECREF(err->obj);
> + qemu_free(err->msg);
> + qemu_free(err);
> +}
> +
> +bool error_is_type(Error *err, const char *fmt)
> +{
> + char *ptr;
> + char *end;
> + char classname[1024];
> +
> + ptr = strstr(fmt, "'class': '");
> + assert(ptr != NULL);
> + ptr += strlen("'class': '");
> +
> + end = strchr(ptr, '\'');
> + assert(end != NULL);
> +
> + memcpy(classname, ptr, (end - ptr));
> + classname[(end - ptr)] = 0;
> +
> + return strcmp(classname, error_get_field(err, "class")) == 0;
> +}
Not used by this series. Except for obvious stuff, I prefer to only add
code that's going to be used right away.
> +
> +void error_propagate(Error **dst_err, Error *local_err)
> +{
> + if (dst_err) {
> + *dst_err = local_err;
> + } else if (local_err) {
> + error_free(local_err);
> + }
> +}
> +
> +QObject *error_get_qobject(Error *err)
> +{
> + QINCREF(err->obj);
> + return QOBJECT(err->obj);
> +}
> +
> +void error_set_qobject(Error **errp, QObject *obj)
> +{
> + Error *err;
> + if (errp == NULL) {
> + return;
> + }
> + err = qemu_mallocz(sizeof(*err));
> + err->obj = qobject_to_qdict(obj);
> + qobject_incref(obj);
> +
> + *errp = err;
> +}
This is not documented. Also, I prefer the documentation & code next to each
other in the same file.
> diff --git a/error.h b/error.h
> new file mode 100644
> index 0000000..317d487
> --- /dev/null
> +++ b/error.h
> @@ -0,0 +1,65 @@
> +/*
> + * QEMU Error Objects
> + *
> + * Copyright IBM, Corp. 2011
> + *
> + * Authors:
> + * Anthony Liguori <aligu...@us.ibm.com>
> + *
> + * This work is licensed under the terms of the GNU LGPL, version 2. See
> + * the COPYING.LIB file in the top-level directory.
> + */
> +#ifndef ERROR_H
> +#define ERROR_H
> +
> +#include <stdbool.h>
> +
> +/**
> + * A class representing internal errors within QEMU. An error has a string
> + * typename and optionally a set of named string parameters.
> + */
> +typedef struct Error Error;
> +
> +/**
> + * Set an indirect pointer to an error given a printf-style format parameter.
> + * Currently, qerror.h defines these error formats. This function is not
> + * meant to be used outside of QEMU.
> + */
> +void error_set(Error **err, const char *fmt, ...)
> + __attribute__((format(printf, 2, 3)));
> +
> +/**
> + * Returns true if an indirect pointer to an error is pointing to a valid
> + * error object.
> + */
> +bool error_is_set(Error **err);
> +
> +/**
> + * Get a human readable representation of an error object.
> + */
> +const char *error_get_pretty(Error *err);
> +
> +/**
> + * Get an individual named error field.
> + */
> +const char *error_get_field(Error *err, const char *field);
> +
> +/**
> + * Propagate an error to an indirect pointer to an error. This function will
> + * always transfer ownership of the error reference and handles the case
> where
> + * dst_err is NULL correctly.
> + */
> +void error_propagate(Error **dst_err, Error *local_err);
> +
> +/**
> + * Free an error object.
> + */
> +void error_free(Error *err);
> +
> +/**
> + * Determine if an error is of a speific type (based on the qerror format).
> + * Non-QEMU users should get the `class' field to identify the error type.
> + */
> +bool error_is_type(Error *err, const char *fmt);
> +
> +#endif
> diff --git a/error_int.h b/error_int.h
> new file mode 100644
> index 0000000..eaba65e
> --- /dev/null
> +++ b/error_int.h
> @@ -0,0 +1,27 @@
> +/*
> + * QEMU Error Objects
> + *
> + * Copyright IBM, Corp. 2011
> + *
> + * Authors:
> + * Anthony Liguori <aligu...@us.ibm.com>
> + *
> + * This work is licensed under the terms of the GNU LGPL, version 2. See
> + * the COPYING.LIB file in the top-level directory.
> + */
> +#ifndef QEMU_ERROR_INT_H
> +#define QEMU_ERROR_INT_H
> +
> +#include "qemu-common.h"
> +#include "qobject.h"
> +#include "error.h"
> +
> +/**
> + * Internal QEMU functions for working with Error.
> + *
> + * These are used to convert QErrors to Errors
> + */
> +QObject *error_get_qobject(Error *err);
> +void error_set_qobject(Error **errp, QObject *obj);
> +
> +#endif
