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From: Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups: comp.lang.c
Subject: Re: 80386 C compiler
Date: Fri, 29 Nov 2024 21:00:20 -0800
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Kaz Kylheku <643-408-1753@kylheku.com> writes:

> On 2024-11-27, James Kuyper <jameskuyper@alumni.caltech.edu> wrote:
>
>> If there weren't a rule mandating the order in which initializers
>> were applied, when two or more initializers affect the same
>> object, it wouldn't be possible to be certain which one overrode
>> the others.

That's wrong.  The priority rule for initializing the same subobject
depends not on order of evaluation but on syntactic order.  There
doesn't have to be a rule for evaluation order to make the order
of subobject overriding be well defined.

> It would make sense for that simply to be a constraint violation;
> two initializations for the same object are being requested.

It isn't that simple.  There are situations where overriding the
initialization of a particular subobject makes sense, and is
useful.  Example:

   typedef struct { int x, y; } Bas;
   typedef struct { Bas b[2]; } Foo;

   Foo
   sample_foo( Bas b ){
      Foo foo = { b, b, .b[1].y = -1 };
      return  foo;
   }

The subobject .b[1].y is overridden, but we can't take the previous
initialization of .b[1] without changing the semantics.