How to compile a julia script? - compilation

Question

I have noticed that the version 0.4.* of julia has a --compile option.
Strangely, I cannot find any documentation about it.
I was trying (in Ubuntu), to compile a julia script to an executable LLVM bytecode file. But until here, I failed:
julia --compile=yes --output-bc test.bc test.jl
Segmentation fault (core dumped)
I also can get this error message:
julia --compile=yes --output-bc test.bc test.jl
ERROR: could not open file boot.jl
This error does not appear anymore, if I put a boot.jl file in the same folder.
How should I do to compile a julia script to an executable/obfuscated bytecode ?
Edit: FYI, my test.jl file contains only print(123)

Answer 1

Here's an example, from a julia source build on OS X, with /tmp/test.jl as:
function foo()
print(123)
end
precompile(foo, ())
And julia/base/userimg.jl as include("/tmp/test.jl")
Execute the following inside the julia/base directory:
julia --compile=yes --output-bc test.bc -J ../usr/lib/julia/inference.ji sysimg.jl
Then run llvm-dis test.bc -o test.ll. Somewhere in the (enormous) image we have the relevant bytecode for the test function:
define internal %jl_value_t* #julia_foo_22542() {
top:
%0 = alloca [4 x %jl_value_t*], align 8, !dbg !51528
...
That said, as of now (Dec. 2015), Julia is not usable for ahead-of-time compilation of stand-alone executables. However, the following may be of interest:
https://github.com/dhoegh/BuildExecutable.jl (doesn't use --output-bc, as yet, but has a nicer user interface and that option would be easy to add)
https://github.com/JuliaLang/julia/pull/13677