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From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: Are there any conformant C compilers?
Date: Fri, 02 Sep 2022 11:50:58 -0700
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Thiago Adams <thiago.adams@gmail.com> writes:
> On Friday, September 2, 2022 at 1:53:06 PM UTC-3, Bart wrote:
>> On 02/09/2022 16:19, Ben Bacarisse wrote: 
>> > Bart <b...@freeuk.com> writes: 
>> > 
>> >>>> The only other actual literal is a string. 
>> >>> How about compound literals? 
>> >> 
>> >> The 'literal' in those is just a term somebody decided use. 
>> > 
>> > They are literals because they describe a specific value in the source 
>> > code. The value is "literally" in the source. 
>> > 
>> >> (Elsewhere I would call them constructors.) 
>> > 
>> > Sure. And the ASCII digit 1 is a constructor for an int value. And a " 
>> > optionally followed by characters and another " is a constructor for a 
>> > char array object. 
>> > 
>> > Both terms work, but the one C has chosen is "literal". 
>> >
>> Some constructors are special: 
>> 
>> 123456 
>> 123.456 
>> "abcdef" 
>> 'A' 
>> 
>> because they can /only/ comprise values known at compile-time. These I 
>> like to call literals. 
>
> Compound literals also are values known  at compile time.

Not necessarily.  A compound literal at block scope can contain
non-constant expressions.

    struct foo { int a; int b; };
    struct foo obj;
    obj = (struct foo) { .a = rand(), .b = rand() };

> For instance:
> ((int []){1, 2, 3})
> or
> ((struct X { int i ; } ){.i = 2})
>
> (
>  by the way, in C23 compound literal can have storage 
>  specifier, static constexpr..
>  Like
>  ((static int []){1, 2, 3})
> )

That's handy.  It means that you can write a compound literal at block
scope whose associated object doesn't vanish at the end of the block.
With `static`, you can return a pointer to it.  It gives you behavior
more similar to string literals.

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for Philips
void Void(void) { Void(); } /* The recursive call of the void */