[Dlang-internal] Detect CTFE in AssignExp:semantic

[Andrei Alexandrescu via Dlang-internal]

On 1/11/17 3:16 PM, Martin Nowak wrote:
> On Wednesday, 11 January 2017 at 09:05:44 UTC, Lucia Cojocaru wrote:
>> The dmd code (e2ir.d and expression.d are of interest):
>> https://github.com/somzzz/dmd/commit/8bccc49ba661567c523545650aad30c01fd25090
>>
>
> Calls for the old dmd<->C-API are very different from template functions
> calls, e.g. take a look at how _xOpEquals is called.
> https://github.com/dlang/dmd/blob/538a895157acdbbfc5869791f9504f7e86b4fdd0/src/clone.d#L496

Cool. That looks different from 
https://github.com/somzzz/dmd/commit/8bccc49ba661567c523545650aad30c01fd25090, 
is the latter appropriate as well? Or perhaps that's why the error with 
reading the variable during compilation?

>> The druntime template:
>
> https://github.com/somzzz/druntime/commit/6cf9cbc6650697d8a038be7076e588601aefe954
>
>
>> The example which doesn't compile is a standalone code snippet which
>> reproduces the error encountered. I started from the code in druntime
>> and simplified it to that point. As of your suggestions, I will
>> simplify it further and come back with another example.
>
> You cannot distinguish between ctfe/non-ctfe during semantic. Only the
> backend/glue layer differs between CTFE (interpret.d) and IR/codegen
> (e2ir).
> If you want to convert a C-API intrinsic to a template function call,
> you'd usually deal with __ctfe in druntime not in the compiler.
> DMD will always call the druntime function and if that happens during
> CTFE, it'll get interpreted.

OK, but the problem here is it indicates a problem at the call site of 
_d_arraycopyT, not inside the implementation. Is there an issue with the 
way the code is generated?

Also, as an aside: the _d_arraycopyT should probably go like this:

D _d_arraycopyT(S, D)(S from, D to) { ... }

You don't need size because it's from[0].sizeof. Correct?


Andrei