On Tuesday, 14 December 2021 at 07:50:48 UTC, evilrat wrote:
There is some missing features like above tail ref and const, there is minor mangling issues that requires pragma mangle sometimes, and other annoying little details.
As far as I can tell from my limited experience, the way D approaches interacting with C++ is sound and extremely useful. Link compatibility goes a very long way.
Unfortunately it's the "annoying little details" that I immediately bumped into. Things that should be no problem at all with just link compatibility, like incorrectly mangled functions (forgetting about 'const' in return types on Windows) and this very, very annoying issue that I can't pass a class by reference but only by pointer.
I can understand that passing a class by value might be out of scope (though it would be possible, since it works for structs just as well), but with pass by reference it's really just D's boneheadedness to try to have its own way.
D is a great language, and I want to use it, but as a stand-alone language it just doesn't have the ecosystem that I need (gamedev). Using it as an integrated scripting language is for me the next best thing to benefit from it in a project that is otherwise C++. With link compatibility and auto-generating some bindings, I can get there eventually, but it's still a lot of work with many manually crafted shims. I am currently willing to invest a lot of time to try to solve this, but I won't rewrite a huge C++ code base just because D can't pass classes by reference.
Other projects will have even more constraints and even less willingness to invest time into such an undertaking and just scrap the idea early on.
C++ link compatibility was a great idea, but if D wants to expand it's user base further, in my opinion it has to polish the interop and be willing to make a few sacrifices on it's end, because that can save everyone else hundreds of hours of tedious work (and maintenance) and thus be the deciding factor for or against using D in a C++ project.
