Julia Error: @ccallable: argument types must be concrete

user_11917277 0
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I am new to Julia and trying to compile a function. My code is something like this and I get an error saying "@ccallable: argument types must be concrete" when I run the code. I also found this is because of the initial value I set to the function. Could anyone help me to solve this problem?

# this doesn't work
Base.@ccallable function test_function(a::Vector{Float64}, b::Float64, c=0.0::Float64)::Vector{Int64}
    c = b + c
    return a
end

# this works
Base.@ccallable function test_function(a::Vector{Float64}, b::Float64, c::Float64)::Vector{Int64}
    c = b + c
    return a
end
packagecompiler.jl julia
2 Answers
user_104479640

For the error itself, the problem is c=0.0::Float64 doesn't annotate the type of c, it asserts that the type of the default value 0.0 is Float64. You can actually check methods(test_function) to confirm this. To annotate c, write this: c::Float64=0, though that's not actually C-compatible.

Bigger picture, I'm confused about what you mean by "compile a function." The code looks like you're using PackageCompiler and making a Julia function callable from C. If you only want to compile a Julia function instead, Julia just does it upon every first call with a unique set of concrete argument types.

user_41321440
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