Cannot use shared library with Distributed.jl

General Usage
,
1

Hi,
I’m trying to use a shared library in a pmap call from Distributed.jl, but can’t seem to make it work.

MWE:
A file mylib.c with this:

#include <stdio.h>

int say_y(int y)
{
    printf("Hello from C: got y = %d.\n", y);
    return y*2;
}

and the julia code:

using Distributed, Libdl
addprocs()
run(`gcc -fPIC -shared -o mylib.so mylib.c`)

@everywhere function get_dlhandler()
    lib = Libdl.dlopen(joinpath(@__DIR__, "mylib.so"))
    symbol = Libdl.dlsym(lib, :say_y)
    return (lib, symbol)
end

@everywhere lib, symbol = get_dlhandler()

map(id->fetch(@spawnat id lib), 1:nprocs())
#=
All pointers but the first are undefined: 
 Ptr{Nothing}(0x000000003ceccb50)
 Ptr{Nothing}(0x0000000000000000)
 Ptr{Nothing}(0x0000000000000000)
 ...
=#

I also tried having a different copy of the shared library mylib.so for each process, without any change.

There must be something I don’t grasp about distributed computing, shared libraries and filesystem interaction, but I can’t seem to find an answer. Any idea as to what I’m doing wrong?

PS: using the library with @ccall works, but I want to keep the library reference in order to avoid opening it again and again:

pmap(y->(@ccall "./mylib.so".say_y(y::Cint)::Cint), 1:10)
# returns [2, 4, 6,..., 20]