On 09/26/22 13:50, Richard W.M. Jones wrote:
> On Mon, Sep 26, 2022 at 09:50:48AM +0100, Daniel P. Berrangé wrote:
>> On Mon, Sep 26, 2022 at 10:18:06AM +0200, Laszlo Ersek wrote:
>>> gcc reports:
>>>
>>>> gui.c:1795:3: error: missing initializer for field ‘padding’ of
>>>> ‘GActionEntry’ {aka ‘const struct _GActionEntry’}
>>>> [-Werror=missing-field-initializers]
>>>> 1795 | { "shutdown", activate_action, NULL, NULL, NULL },
>>>>
>>>> gui.c:1796:3: error: missing initializer for field ‘padding’ of
>>>> ‘GActionEntry’ {aka ‘const struct _GActionEntry’}
>>>> [-Werror=missing-field-initializers]
>>>> 1796 | { "reboot", activate_action, NULL, NULL, NULL },
>>>
>>> I've found this only now because:
>>>
>>> - this is the first time I'm building virt-p2v with GTK3,
>
> One of the problems of having several different build axes :-(
Interestingly, gtk3-devel had not been installed on my workstation; I
don't even remember why I (apparently) only installed gtk2-devel. (And
then, and this is subjective of course, I actually think gtk2 looked
better. :/)
>
>>> - the "shutdown_actions" array depends on USE_POPOVERS which depends on
>>> GTK3 being selected,
>>>
>>> - the "missing-field-initializers" warning (treated as an error) has
>>> recently been enabled via "-Wextra" in commit 391f9833d398 ("p2v-c.m4:
>>> elicit a stricter set of warnings from gcc", 2022-09-23).
>>>
>>> The C-language documentation for GActionEntry is silent on the "padding"
>>> array:
>>>
>>> https://docs.gtk.org/gio/struct.ActionEntry.html
>>>
>>> However, the D-language docs expose it:
>>>
>>> https://api.gtkd.org/gio.c.types.GActionEntry.html
>>>
>>> Provide the missing field initializer.
>>>
>>> Signed-off-by: Laszlo Ersek <ler...@redhat.com>
>>> ---
>>> gui.c | 4 ++--
>>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/gui.c b/gui.c
>>> index 49301d9a985b..4faaa710ed90 100644
>>> --- a/gui.c
>>> +++ b/gui.c
>>> @@ -1792,8 +1792,8 @@ static gboolean close_running_dialog (GtkWidget *w,
>>> GdkEvent *event, gpointer da
>>>
>>> #ifdef USE_POPOVERS
>>> static const GActionEntry shutdown_actions[] = {
>>> - { "shutdown", activate_action, NULL, NULL, NULL },
>>> - { "reboot", activate_action, NULL, NULL, NULL },
>>> + { "shutdown", activate_action, NULL, NULL, NULL, { 0 } },
>>> + { "reboot", activate_action, NULL, NULL, NULL, { 0 } },
>>> };
>>
>> Notice the header decl says 'padding' is private hence why it is
>> not documented.
>>
>> struct _GActionEntry
>> {
>> const gchar *name;
>>
>> void (* activate) (GSimpleAction *action,
>> GVariant *parameter,
>> gpointer user_data);
>>
>> const gchar *parameter_type;
>>
>> const gchar *state;
>>
>> void (* change_state) (GSimpleAction *action,
>> GVariant *value,
>> gpointer user_data);
>>
>> /*< private >*/
>> gsize padding[3];
>> };
>>
>>
>> The purpose of this 'padding' entry is to reserve space in the struct
>> for future usage. Apps should never touch the padding field, since it
>> can change in future. ie that 3 element array can turn into three
>> separate public fields later, and then the compound initializer above
>> would be invalid.
>>
>> The right way to declare this is using named initializers:
>>
>> { .name = "shutdown", .activate = activate_action },
>> { .name = "reboot", .activate = activate_action },
>
> Yes I agree, if that shuts up the -Wextra warning.
It should; the gcc documentation says about -Wmissing-field-initializers
that it does not warn about designated initializers, such as in:
struct s { int f, g, h; };
struct s x = { .f = 3, .g = 4 };
Laszlo
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