Using the Standard Library with C++ Interop

[Adam D. Ruppe]

On Friday, 5 February 2021 at 21:04:00 UTC, wolfiesnotfine wrote:
> however sse() from core.cpuid is incorrectly reporting as 
> false. The function properly returns true if it's not called 
> from C++ but instead a D main function.

That makes me think it is a static constructor, and indeed there 
is one here:

https://github.com/dlang/druntime/blob/master/src/core/cpuid.d#L1068


Static constructors are normally run during druntime 
initialization, but betterC never uses druntime and thus doesn't 
initialize it.

You might be able to just call that function directly with some 
pragma(mangle) hacks (get the symbol name out of the binary, 
probably something like _D4core5cpuid6__ctor or something along 
those lines, then declare function like `pragma(mangle, "that 
name") extern void initCpuId();` and just call it at some point), 
or copy/paste the source out into your code and call it that way.

The copy/paste is surely easier and more likely to work since 
even if you get the symbol name, it probably isn't linked in with 
-betterC since that skips linking the runtime code entirely.


tbh I'd say just don't use betterC, you can still runtime init 
from C++ and be judicious in what features you use to keep it 
more minimal.