[fpc-devel] Dangerous optimization in CASE..OF

[Martok]

Am 25.07.2017 um 19:31 schrieb Martok:
> As has just been pointed out to me, we all misdiagnosed that example.
Turns out this is not a new question, there is actually a very thorough
treatment of that very issue on SO:
<https://stackoverflow.com/questions/18195312/what-happens-if-you-static-cast-invalid-value-to-enum-class>

(Continue reading after the mention of CWG 1766, the interesting part is what
"representable range" means)

The simple answer however is: a C++ enum with fixed base type (FPC analogue: any
setting other than {$PACKENUM DEFAULT}), any value of the base type is valid.
C++ enums *without* base type may also have a smaller range than int, but always
a power-of-two. That would mean one could mask with that size (we already
generate the masking sometimes) and make the jumptable larger, saving a Jx at
the expense of a larger table.

So the question boils down to: do we want C-Style Enums to behave like in
C-dialects, or just look like they do?

If we do, there's a very simple solution: by setting a fixed $Z option, the
programmer specifically *chose* Low-Level enums. We could just honour that and
be done with it.

--
Martok