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Re: [Qemu-devel] [PATCH v4] hmp: Allow for error message hints on HMP
From: |
Markus Armbruster |
Subject: |
Re: [Qemu-devel] [PATCH v4] hmp: Allow for error message hints on HMP |
Date: |
Thu, 10 Sep 2015 20:05:09 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) |
Eric Blake <address@hidden> writes:
> Commits 7216ae3d and d2828429 disabled some error message hints,
> all because a change to use modern error reporting meant that the
> hint would be output prior to the actual error. Fix this by making
> hints a first-class member of Error.
>
> For example, we are now back to the pleasant:
>
> $ qemu-system-x86_64 --nodefaults -S --vnc :0 --chardev null,id=,
> qemu-system-x86_64: --chardev null,id=,: Parameter 'id' expects an identifier
> Identifiers consist of letters, digits, '-', '.', '_', starting with a
> letter.
>
> Signed-off-by: Eric Blake <address@hidden>
> Reviewed-by: Paolo Bonzini <address@hidden>
> ---
>
> v4: add R-b, rebase to latest qemu.git
> v3: don't crash when freeing error without hint [Eric]
> v2: use GString instead of rolling our own O(n^2) string concast [Paolo]
>
> include/qapi/error.h | 7 +++++++
> qdev-monitor.c | 42 ++++++++++++++----------------------------
> util/error.c | 32 ++++++++++++++++++++++++++++++++
> util/qemu-option.c | 11 ++++-------
> 4 files changed, 57 insertions(+), 35 deletions(-)
>
> diff --git a/include/qapi/error.h b/include/qapi/error.h
> index 426d5ea..d7878c3 100644
> --- a/include/qapi/error.h
> +++ b/include/qapi/error.h
> @@ -155,6 +155,13 @@ void error_setg_win32_internal(Error **errp,
> */
> void error_propagate(Error **dst_errp, Error *local_err);
>
> +/**
> + * Append a printf-style human-readable explanation to an existing error.
> + * May be called multiple times, and safe if @errp is NULL.
> + */
> +void error_append_hint(Error **errp, const char *fmt, ...)
> + GCC_FMT_ATTR(2, 3);
> +
> /*
> * Convenience function to report open() failure.
> */
> diff --git a/qdev-monitor.c b/qdev-monitor.c
> index f9e2d62..0bf7f83 100644
> --- a/qdev-monitor.c
> +++ b/qdev-monitor.c
> @@ -289,37 +289,35 @@ static Object *qdev_get_peripheral_anon(void)
> return dev;
> }
>
> -#if 0 /* conversion from qerror_report() to error_set() broke their use */
> -static void qbus_list_bus(DeviceState *dev)
> +static void qbus_list_bus(DeviceState *dev, Error **errp)
> {
> BusState *child;
> const char *sep = " ";
>
> - error_printf("child buses at \"%s\":",
> - dev->id ? dev->id : object_get_typename(OBJECT(dev)));
> + error_append_hint(errp, "child buses at \"%s\":",
> + dev->id ? dev->id : object_get_typename(OBJECT(dev)));
> QLIST_FOREACH(child, &dev->child_bus, sibling) {
> - error_printf("%s\"%s\"", sep, child->name);
> + error_append_hint(errp, "%s\"%s\"", sep, child->name);
> sep = ", ";
> }
> - error_printf("\n");
> }
>
> -static void qbus_list_dev(BusState *bus)
> +static void qbus_list_dev(BusState *bus, Error **errp)
> {
> BusChild *kid;
> const char *sep = " ";
>
> - error_printf("devices at \"%s\":", bus->name);
> + error_append_hint(errp, "devices at \"%s\":", bus->name);
> QTAILQ_FOREACH(kid, &bus->children, sibling) {
> DeviceState *dev = kid->child;
> - error_printf("%s\"%s\"", sep, object_get_typename(OBJECT(dev)));
> - if (dev->id)
> - error_printf("/\"%s\"", dev->id);
> + error_append_hint(errp, "%s\"%s\"", sep,
> + object_get_typename(OBJECT(dev)));
> + if (dev->id) {
> + error_append_hint(errp, "/\"%s\"", dev->id);
> + }
> sep = ", ";
> }
> - error_printf("\n");
> }
> -#endif
>
> static BusState *qbus_find_bus(DeviceState *dev, char *elem)
> {
> @@ -461,11 +459,7 @@ static BusState *qbus_find(const char *path, Error
> **errp)
> if (!dev) {
> error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
> "Device '%s' not found", elem);
> -#if 0 /* conversion from qerror_report() to error_set() broke this: */
> - if (!monitor_cur_is_qmp()) {
> - qbus_list_dev(bus);
> - }
> -#endif
> + qbus_list_dev(bus, errp);
> return NULL;
> }
>
> @@ -483,11 +477,7 @@ static BusState *qbus_find(const char *path, Error
> **errp)
> if (dev->num_child_bus) {
> error_setg(errp, "Device '%s' has multiple child buses",
> elem);
> -#if 0 /* conversion from qerror_report() to error_set() broke this: */
> - if (!monitor_cur_is_qmp()) {
> - qbus_list_bus(dev);
> - }
> -#endif
> + qbus_list_bus(dev, errp);
> } else {
> error_setg(errp, "Device '%s' has no child bus", elem);
> }
> @@ -503,11 +493,7 @@ static BusState *qbus_find(const char *path, Error
> **errp)
> bus = qbus_find_bus(dev, elem);
> if (!bus) {
> error_setg(errp, "Bus '%s' not found", elem);
> -#if 0 /* conversion from qerror_report() to error_set() broke this: */
> - if (!monitor_cur_is_qmp()) {
> - qbus_list_bus(dev);
> - }
> -#endif
> + qbus_list_bus(dev, errp);
> return NULL;
> }
> }
> diff --git a/util/error.c b/util/error.c
> index cdb726c..9dd474f 100644
> --- a/util/error.c
> +++ b/util/error.c
> @@ -20,6 +20,7 @@ struct Error
> ErrorClass err_class;
> const char *src, *func;
> int line;
> + GString *hint;
> };
>
> Error *error_abort;
> @@ -115,6 +116,28 @@ void error_setg_file_open_internal(Error **errp,
> "Could not open '%s'", filename);
> }
>
> +void error_append_hint(Error **errp, const char *fmt, ...)
> +{
> + va_list ap;
> + int saved_errno = errno;
> + Error *err;
> +
> + if (!errp) {
> + return;
> + }
> + err = *errp;
> + assert(err && errp != &error_abort);
> +
> + if (!err->hint) {
> + err->hint = g_string_new(NULL);
> + }
> + va_start(ap, fmt);
> + g_string_append_vprintf(err->hint, fmt, ap);
> + va_end(ap);
> +
> + errno = saved_errno;
> +}
> +
> #ifdef _WIN32
>
> void error_setg_win32_internal(Error **errp,
> @@ -151,6 +174,9 @@ Error *error_copy(const Error *err)
> err_new = g_malloc0(sizeof(*err));
> err_new->msg = g_strdup(err->msg);
> err_new->err_class = err->err_class;
> + if (err->hint) {
> + err_new->hint = g_string_new(err->hint->str);
> + }
>
> return err_new;
> }
> @@ -168,6 +194,9 @@ const char *error_get_pretty(Error *err)
> void error_report_err(Error *err)
> {
> error_report("%s", error_get_pretty(err));
> + if (err->hint) {
> + error_printf_unless_qmp("%s\n", err->hint->str);
> + }
> error_free(err);
> }
>
> @@ -175,6 +204,9 @@ void error_free(Error *err)
> {
> if (err) {
> g_free(err->msg);
> + if (err->hint) {
> + g_string_free(err->hint, true);
> + }
> g_free(err);
> }
> }
Once again, GLib demonstrates its lack of taste.
> diff --git a/util/qemu-option.c b/util/qemu-option.c
> index efd6f02..6c76ed2 100644
> --- a/util/qemu-option.c
> +++ b/util/qemu-option.c
> @@ -205,10 +205,8 @@ void parse_option_size(const char *name, const char
> *value,
> break;
> default:
> error_setg(errp, QERR_INVALID_PARAMETER_VALUE, name, "a size");
> -#if 0 /* conversion from qerror_report() to error_set() broke this: */
> - error_printf_unless_qmp("You may use k, M, G or T suffixes for "
> - "kilobytes, megabytes, gigabytes and terabytes.\n");
> -#endif
> + error_append_hint(errp, "You may use k, M, G or T suffixes for "
> + "kilobytes, megabytes, gigabytes and terabytes.");
> return;
> }
> } else {
> @@ -648,9 +646,8 @@ QemuOpts *qemu_opts_create(QemuOptsList *list, const char
> *id,
> if (!id_wellformed(id)) {
> error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "id",
> "an identifier");
> -#if 0 /* conversion from qerror_report() to error_set() broke this: */
> - error_printf_unless_qmp("Identifiers consist of letters, digits,
> '-', '.', '_', starting with a letter.\n");
> -#endif
> + error_append_hint(errp, "Identifiers consist of letters, digits,
> "
> + "'-', '.', '_', starting with a letter.");
> return NULL;
> }
> opts = qemu_opts_find(list, id);
I'll take this through my tree. Thanks!