On 12/13/2016 02:32 PM, Jason Merrill wrote:
On 12/13/2016 03:25 PM, Martin Sebor wrote:
On 12/13/2016 12:06 PM, Jason Merrill wrote:
On 12/09/2016 07:46 PM, Martin Sebor wrote:
On 12/09/2016 02:49 PM, Jason Merrill wrote:
On Fri, Dec 9, 2016 at 11:33 AM, Martin Sebor <mse...@gmail.com>
wrote:
For flexible array members, because they're not in C++, we get to
make up the rules that make the most sense to us. IMO, they should
fit in well with the rest of the language.
I disagree; we should support C code, but flexible arrays don't really
fit with the C++ object model, so I don't think trying to do anything
clever with them in constructors is worthwhile.
With the suggested approach the array becomes just an ordinary member.
It's not a flexible array member anymore because its bound is deduced
from the initializer (it just looks like one). The NSDMI char a[] =
"foo" syntax is just a shorthand for char a[4] = "foo".
That would mean that the size of the class varies with its initializer,
which again gets into not fitting with the C++ object model.
Okay, I accept the challenge of finding a case where the size
of a class depends on an initializer expression :)
Here's one:
constexpr long f (int) { return 1; }
constexpr long f (long) { return LONG_MAX; };
struct A { // sizeof (A) == 4
enum E { i = f (0) } e;
};
struct B { // sizeof (B) == 8
enum E { i = f (0L) } e;
};
It's not exactly the same but I think it's close enough to argue
that deducing the array size from its initializer wouldn't go
against the established model.
I don't see the similarity; A and B both have constant size.
Sure, just as C and D below do today
struct C { // sizeof (C) == 4
char a[4] = "abc";
};
struct D { // sizeof (D) == 8
char a[8] = "abcdefg";
};
and as would E and F below with what I suggest:
struct E { // sizeof (E) == 4
char a[] = "abc";
};
struct F { // sizeof (F) == 8
char a[] = "abcdefg";
};
Where is the disconnect?
I'm not suggesting that the size of an object of a class change
depending on how the member array is initialized in each ctor
initializer list (if that's how it came across).
Martin
