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From: Thiago Adams <thiago.adams@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: c initialization algorithm
Date: Tue, 15 Oct 2024 08:12:35 -0300
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On 14/10/2024 08:14, Thiago Adams wrote:
> On 14/10/2024 02:00, Tim Rentsch wrote:
>> Kaz Kylheku <643-408-1753@kylheku.com> writes:
>>
>>> On 2024-10-13, Thiago Adams <thiago.adams@gmail.com> wrote:
>>>
>>>> The algorithm for C initialization as described in the standard
>>>> and implemented in gcc allow this.
>>>>
>>>> struct X{
>>>>       int a,b,c;
>>>> };
>>>>
>>>> int main()
>>>> {
>>>>       struct X x = {.a=1,2,3,.a=1, 2, 3};
>>>> }
>>>>
>>>> https://godbolt.org/z/7naedbEM6
>>>>
>>>> Basically, when a designed initializer is found the "cursor" goes
>>>> to that member and the following members are initialized in
>>>> order.
>>>
>>>   I do not suspect that therw is an observable order.  I.e. as
>>>   in a required order considered observable behavior.
>>
>> Have you checked to C standard to see what it says about that?

I'm not only interested in this part, but since it raised some doubts, I 
decided to do some checks

#include <stdio.h>

struct X {
     int i;
};

int f() {
     printf("f");
     return 1;
}

int main() {
     struct X x = {.i = f(), .i = f() };
}

https://godbolt.org/z/rf984cGMM

There is a warning in this sample and f is called just once.