Yigal Chripun wrote:
Lars T. Kyllingstad Wrote:
I was going to protest: "But what about const struct members? Should the
size of the following struct depend on whether the compiler determines
it can optimize by turning its const member into a manifest constant?"
struct Foo { const int bar = 123; }
But then I decided to actually try it with the current DMD2, and found
that the compiler does just that!
writeln(Foo.sizeof); // Prints "1", not "4"
Foo foo;
auto p = &foo.bar; // Error: constant 123 is not an lvalue
What's going on? Is this intended behaviour?
-Lars
what D version?
DMD 2.035.
in D1 const is a manifest constant as far as I know.
Yes, but in D2 the spec says that const is a constant view of mutable
data. There isn't (or at least I can't find) mention that struct members
are excepted from this rule.
to answer to general question, "what about structs":
I'd say that the same rules should apply just like inside functions.
struct Foo { const int num = 42; } // num should be a manifest const
can you give a use-case/example where you wouldn't want to do that but rather store the constant in the struct?
In any case where a different view of the same data is non-const. Or
would you also disallow casting away const-ness?
-Lars
