GAgavinray·Sep 13, 2021
Now if only a full binding generator for C and C++ headers to Nim was done (the reverse), the language would really be cooking!
"What do you mean, Nim has two of these already?"
Yeah, I know, and -- not to hurt anyone's feelings -- but: they kind of suck. And there's no way I see them able to be extended to do the job fully, based on the way they're currently built.
Those are some bold claims to make!
So before I get stoned to death (no offense to the authors, I am grateful that they exist and have used them both) let me attempt an explanation and back up these statements.
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To start off, the two tools available are "c2nim" and "nimterop". c2nim is a Nim official library, while nimterop is a community library.
https://github.com/nim-lang/c2nim
https://github.com/nimterop/nimterop
To preface this: I've spent a fair amount of time on
Read the rest
the "codegen of bindings for interop from C/C++ headers" problem. The first thing I did was reach out to people who spent months or years on this problem and ask them what worked and what didn't. (I had no clue where to start and figured lots of smart people have done this before)
Consistently, what I heard was (roughly):
"If you want to programmatically interact with information about C/C++ units, you want to use the LLVM/clang ecosystem. You're going to think you can do what you want from 'libclang', the C API. But what you'll find out after sinking months of your time is that libclang DOESN'T expose enough info about the AST for certain scenarios, and there is ABSOLUTELY ZERO WAY to get it. So you'll need to use libTooling, which is C++, and has the full AST available."
I've found this to be true, with the exception that a few people have taken to "augmenting" libclang with extra bindings to libTooling functions or other C++-only methods.
Most notably is Tanner Gooding & Co's "libClangSharp" from the Microsoft "ClangSharp" project, and PathogenDavid's "Biohazrd" libraries (which again are a sort of enhanced fork based on ClangSharp):
https://github.com/microsoft/ClangSharp # See "/sources/libClangSharp"
https://github.com/InfectedLibraries/Biohazrd
Okay so with that out of the way, my long-winded point is:
- c2nim is a custom C lexer/parser written in Nim, with zero support for C++
- nimterop uses tree-sitter, which isn't bad but it's certainly no "libTooling"
Neither tool supports C++, and edgecases (in either text or syntax) will still outright break them/they don't know how to handle. I had one where an unprintable unicode character caused c2nim to freeze indefinitely.
Nimterop is also dead as far as I understand -- last active commit period was about ~1 yr ago.
I'm hard to convince to the path to success here doesn't involve leaning on the collective decades of man-hours of engineering put into clang/LLVM. C++ is a nightmare of a specification, a veritable cluster-fuck of complexity.
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As a side note, I've had the opportunity to speak to one of the Nim maintainers (Timothee Cour) about this and the future here, and he's expressed interest in having a good story for easy type-safe C++ interop via binding generation and also believes it's important.
So hopefully this is something we'll see pop up eventually.
Maybe I'll take a crack at myself using ClangSharp (or it's XML output format, using TypeScript/Python to munge the XML and spit out code) but there aren't enough hours in a day to do all the interesting things =(