On Wed, 03 Aug 2011 06:35:08 -0400, simendsjo <simend...@gmail.com> wrote:
void main() {assert(is(typeof("") == typeof("".idup))); // both is immutable(char)[]assert("" !is null); assert("".idup !is null); // fails - s is null. Why? }
An empty string manifest constant (i.e. string literal) still must have a valid pointer, because it's mandated that the string have a zero byte appended to it. This is so you can pass it to C functions which expect null-terminated strings.
So essentially, there is a '\0' in memory, and "" points to that character with a length of 0
However, idup calls a runtime function which *purposely* asks to make a copy. However, it's *NOT* required to copy the 'zero after the string' part.
The implementation, knowing that a null array is equivalent to an empty array, is going to return null to avoid the performance penalty of allocating a block that won't be used. If you append, it will simply allocate a block as needed.
I see no reason the runtime should waste cycles or a perfectly good 16-byte buffer to give you an empty array.
Definitely functions as designed, not a bug. If you would like different behavior, you are going to have to have a really really good use case to get this changed.
-Steve
