Re: [Qemu-devel] [PATCH 03/11] add a generic Error object

[Blue Swirl]

On Fri, Mar 11, 2011 at 11:00 PM, Anthony Liguori <address@hidden> 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.
>
> Signed-off-by: Anthony Liguori <address@hidden>
>
> 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
>
> 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   <address@hidden>
> + *
> + * 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;
> +    const char *fmt;
> +    char *msg;
> +};
> +
> +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));
> +    }
> +
> +    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;
> +}
> +
> +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;
> +}
> diff --git a/error.h b/error.h
> new file mode 100644

The name is too generic, it could conflict with system headers. At
least I have /usr/include/error.h.

> index 0000000..317d487
> --- /dev/null
> +++ b/error.h
> @@ -0,0 +1,65 @@
> +/*
> + * QEMU Error Objects
> + *
> + * Copyright IBM, Corp. 2011
> + *
> + * Authors:
> + *  Anthony Liguori   <address@hidden>
> + *
> + * 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

This #define could also conflict with system headers. In my system,
_ERROR_H is used, but who knows all error.h files out there?