How to set nthreads for library at load time

[visr]

In #113 the number of threads is set to 1, with the option to change it at compile time.

I am compiling Julia code to a library with JuliaC, and used to set the threads at runtime from a Rust CLI by setting JULIA_NUM_THREADS, which worked fine (code here if interested).

I'm fine with defaulting to 1, but I don't see how I can control it at runtime. I see testset "jl_options applied at runtime (library)" but that only seems to read out the values at runtime.

Or should really not do this? I don't understand what in #112 is meant by until it has multi-threading / chained signal support. EDIT: just found JuliaLang/julia#61319

[visr]

Since I didn't want to be stuck on an older JuliaC version, in Deltares/Ribasim#3151 I added c_sources = ["build/set_julia_threads.c"] which adds C API to our library to set the number of threads before Julia is initialized. When nthreads > 1, signal handling is turned on as well.