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From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.c
Subject: Re: C++ features for C
Date: Fri, 11 May 2018 15:38:58 -0700
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Thiago Adams <thiago.adams@gmail.com> writes:
> On Friday, May 11, 2018 at 4:59:34 PM UTC-3, Ian Collins wrote:
[...]
>> You overlooked the potentially most useful feature: real constants and 
>> constant expressions.
>
> Do you mean?
>
> constexpr double PI2 = 3.141592653589793;
>
> I don't like because of this:
>
> int main() {
>     constexpr double PI2 = 3.141592653589793;
>     const double *PI = &PI2;
> 	
>     printf("%p\n", PI);
>     return 0;
> }
>
> Why it has address?

Apparently the `constexpr double ...` declaration defines an object
that, like any object, has an address -- and ensures that the name
of that object is a constant expression.  (I haven't checked the C++
standard on this point so I'm not certain of the details.)

Presumably if you don't refer to the address of PI2, the compiler
could choose not to allocate storage for it.

I can see the point of wanting a construct that creates a constant
value (as `enum { answer = 42 };` does for constants of type int).
But what problem does the fact that PI2 has an address actually
cause?

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"