Type hierarchy within Clang.jl

freeman · August 7, 2022, 11:02pm

I’m using Clang.jl to automatically generate julia wrappers over C structs, lets call them MyType1, MyType2, etc:

struct MyType1
    # generated by Clang.jl
end
struct MyType2
    # generated by Clang.jl
end

However, these are (as all concretes types by default) direct subtypes of Any. Instead I would like the generated types to be

abstract type AbstractMyType end
abstract type AbstractMyType1 <: AbstractMyType end
abstract type AbstractMyType2 <: AbstractMyType end
(...)
struct MyType1 <: AbstractMyType1
    # generated by Clang.jl
end
struct MyType2 <: AbstractMyType2
    # generated by Clang.jl
end

Is this possible?

Gnimuc · August 8, 2022, 12:33pm

It’s possible as long as you know how to manipulate Julia AST.

github.com

JuliaInterop/Clang.jl/blob/39e3a25a6e932b48a5fa508e680de53296403627/docs/src/generator.md#rewrite-expressions-before-printing

# Generator Tutorial

## Tutorial on wrapping a JLL package
In most situations, Clang.jl is used to export a Julia interface to a C library managed by a JLL package. A JLL package wraps an artifact which provides a shared library that can be called with the `ccall` syntax and headers suitable for a C compiler. Clang.jl can translate the C headers into Julia files that can be directly used like normal Julia functions and types.

The general workflow of wrapping a JLL package is as follows.

1. Locate the C headers relative to the artifact directory.
2. Find the compiler flags needed to parse these headers.
3. Create a `.toml` file with generator options.
4. Build a context with the above three and run.
5. Test and troubleshoot the wrapper.

### Create a default generator
A generator context consists of a list of headers, a list of compiler flags, and generator options. The example below creates a typical context and runs the generator.
```julia
using Clang.Generators
using Clang.LibClang.Clang_jll

cd(@__DIR__)

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