ImportC and #include files

[jmh530]

On Monday, 8 May 2023 at 15:57:01 UTC, bachmeier wrote:
> On Monday, 8 May 2023 at 15:50:09 UTC, jmh530 wrote:
>> On Monday, 8 May 2023 at 15:34:32 UTC, jmh530 wrote:
>>> [snip]
>>> I was assuming that importC would re-write that to an enum 
>>> that I could use directly in the D file, but the spec says 
>>> that it doesn't support all uses of metaprogramming with 
>>> these. You think that's what I'm running into?
>>
>> Hmm, I'm not sure how much sense that makes since I'm able to 
>> use it in the .c file...
>
> To my knowledge, you're only able to use them in .c files. .d 
> files aren't run through the preprocessor and I don't know of 
> any way to access a C macro from D...but maybe I'm wrong. I've 
> been using core.stdc.

If you have a simple #define in a .c file, you can access it from 
a .d file. I tried the importC spec example with `#define COLOR 
0x123456` getting re-written to `enum COLOR = 0x123456;` and it 
worked.

The HUGE_VAL macro is a little more complicated. It relies on #if 
and it calls some `__builtin_huge_val`. However, if I have 
`static double LARGE_VAL = HUGE_VAL` in the .c file, I was able 
to access LARGE_VAL in the .d file as expected. So the 
preprocessor is able to run, but maybe it's not creating the enum 
version due to the other macros going on.