Function as data breaks in threading block

[jnkh]

When functions are used as data inside a threading block, it (occasionally) results in a segmentation fault. When the same function is called as a locally defined function, the program runs smoothly.

Here is a minimal example illustrating this. We are calling the function fn(x) in two different ways. Once as is, and once as a data component of a type. It breaks only in the second case.

using Base.Threads

type CarryFunction
    fn::Function
end

alpha = 0.1
fn(x) = alpha*x

function use_anonymous(N::Int, c::CarryFunction)
    a = zeros(N)
    @threads all for i in 1:length(a)
        # a[i] = fn(i) #NO SEGFAULT
        a[i] = c.fn(i) #SEGFAULT (sometimes... but not always!)
    end
    println(a[1],a[end])
end

length = 10000
repetitions = 100
for j = 1:repetitions
    use_anonymous(length,CarryFunction(fn))
end

[yuyichao]

I can't reproduce on #14190 . There where some similar segfaults that I pushed separately so your particular problem might already be fixed on master. Note that you also need to remove the all parameter to the @thread macro now.

[JeffBezanson]

Possibly dup of #11857

[yuyichao]

Likely but hard to tell since none of these have backtraces.......

At least this one is probably reproducible on a more recent master?