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From: Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups: comp.lang.c
Subject: Re: 80386 C compiler
Date: Wed, 27 Nov 2024 19:26:21 -0800
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Kaz Kylheku <643-408-1753@kylheku.com> writes:

> On 2024-11-25, Rosario19 <Ros@invalid.invalid> wrote:
>
>> On Mon, 25 Nov 2024 18:23:58 -0000 (UTC), Kaz Kylheku  wrote:
>>
>>> void fn(int a)
>>> {
>>>   int x[3] = { foo(), bar(), a }; /* not in C90 */
>>
>> is in the above foo() called before bar()?
>
> No, you cannot rely on that.  Maybe it's fixed in a more recent
> standard, but C99 (which I happen to have open in a PDF reader
> tab) stated that "The order in which any side effects occur among
> the initialization list expressions is unspecified.".  This
> implies that there is no sequence point between any two
> initializing expressions, which means we don't know whose
> expression's function call takes place first.

Challenge exercise for C standard enthusiasts:  It is possible
(in C99 and later) to write an initializer for x[] that puts
in the same values as the initializer above, but guarantees
foo() is called before bar().  Hint:  nothing else is needed
besides a different writing of the initializer for x[] (still
an array of length 3).  How to do it?