On 05/31/2018 06:40 PM, Jonathan M Davis wrote:
On Thursday, May 31, 2018 14:29:13 Manu via Digitalmars-d wrote:
"CTFE
Digests do not work in CTFE"
That's an unfortunate limitation... why is, those things? :(
If I had to guess without looking at the code? I would guess that it's doing
various casts to hash stuff, and no kind of reintpret cast is allowed in
CTFE. But really, you'd have to actually run the code, see what works and
what doesn't, and look at each error you get when it doesn't to see what
it's doing that can't be done during CTFE. Depending on what it's doing, it
may be possible to make it work during CTFE, or it may not. CTFE can do a
lot, but there's also a lot that it can't do - especially if you start doing
anything low level.
- Jonathan M Davis
I know the SHA1 implementation uses some inline asm. Although, now that
I think about it, I think that might just be one specialization of the
implementation, not the only implementation.
Regardless, I do know that std.digest dates back a long time to when
CTFE was WAY more limited that it is today. Most likely, CTFE at the
time probably just wasn't quite up to the task, so it was simply left as
runtime-only. A lot of Phobos was like that back then.
Heck, I wouldn't even be surprised if that note in the docs turned out
to be outdated and it had magically started working at CTFE at some
point. But even if not, I'd say it's almost certainly just a classic
case of "Nobody's needed it badly enough yet to get it working."
