Implement variadic function

[melonedo]

I have manually tested this implementation strategy with Julia's default printf, although this can not be done automatically.

fix #146 , fix #17

[Gnimuc]

By Julia's default printf, you mean the @printf macro in Ptrinf or the printf in Libc?

[Gnimuc]

CImGui.jl has some use cases for this feature, you could give it a test and submit a PR there. IIRC, LibCURL.jl also has some variadic functions, it might have some test cases as well.

https://github.com/JuliaImGui/LibCImGui.jl/blob/9af63ee69dc109000dabdb30ef86073d546738c3/src/LibCImGui.jl#L39-L90

[melonedo]

By Julia's default printf, you mean the @printf macro in Ptrinf or the printf in Libc?

Substitute the $libname.$funcname part for printf or scanf, then the code works.

@generated function scanf(s, va_list...)
        va_list = map(enumerate(to_c_type.(va_list))) do (ind, type)
                :(va_list[$ind]::$type)
            end
        :(@ccall(scanf(s::Ptr{Cchar}; $(va_list...))::Cint))
    end
a = Ref(0)
scanf("%d", a)
# Enter 123
println(a[]) # => 123

[melonedo]

CImGui.jl has some use cases for this feature, you could give it a test and submit a PR there.

Thanks! I'll check it out.

[Gnimuc]

I think it's succinct to give users full control of the types of varargs, just like what they need to do when using @ccall. But to_c_type also has some use cases where users might want to hack into the @generated function and insert their own implementation of to_c_type.

@generated function scanf(s, args::Vararg{Any,N}) where {N}
        varargs = (:(args[$i]::$(args[i])) for i = 1:N)
        :(@ccall(scanf(s::Ptr{Cchar}; $(varargs...))::Cint))
end

[melonedo]

CImGui.jl has some use cases for this feature, you could give it a test and submit a PR there. IIRC, LibCURL.jl also has some variadic functions, it might have some test cases as well.

https://github.com/JuliaImGui/LibCImGui.jl/blob/9af63ee69dc109000dabdb30ef86073d546738c3/src/LibCImGui.jl#L39-L90

Unfortunately both CimGui.jl and LibCimGui.jl have few tests, so I forked LibCURL.jl and tested on Downloads.jl, and it looks fine.

[Gnimuc]

This is great! I would give it a battle test if I could find some time.

[Gnimuc]

I'm going to merge this. @melonedo could you rebase the commit history to be a little bit cleaner? For example, one commit for the implementation and another one for docs.

[melonedo]

Should I force-push the combined commits here?

[Gnimuc]

Yup.