What does the binary julia-debug do that julia does not? I assume it is built with debugging options on. Is there a way it can benefit someone programming in Julia or is it mainly for those who are developing for the Julia language itself?

just for developing Julia itself. It allows to debug the C/C++ part of the Julia source code.

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OK great. I really appreciate the quick answer!

It also allows better debugging of non-C/C++ part but shouldn’t be needed for most package debugging.

What does it mean if I get errors like this in debug mode, but not normally?

julia> using SIMDArrays
[ Info: Precompiling SIMDArrays [604d08c6-8d09-11e8-1189-87850a518ab4]
julia-debug: /home/chriselrod/Documents/languages/jdev/src/gf.c:1188: check_ambiguous_visitor: Assertion `!jl_subtype((jl_value_t*)sig, (jl_value_t*)type)' failed.

signal (6): Aborted

I was hoping this would make it easier to track down segfaults.

It does mean that you should write a bug report on this in the julia github repo :wink:

Assertions are usually stripped in the release version (not sure if julia bypasses this) and thus its clear that the assertion will only kick in in debug mode. But since assertions should never happen, you might have hit a a real bug.