Crash using binary_memory on a dead process

[digitalcora]

erlang:process_info/2 can return undefined — the docs don't explain why, but it's in the typespec and definitely happens when the queried process is dead. If using recon:info/2 with the binary_memory attribute, Recon doesn't handle this return value and crashes in an internal call to proc_fake (see here).

Additionally, the typespec for recon:info/2 doesn't include undefined as a possible return value, even though it can return this (e.g. if used on a dead process).

Example in Elixir, because I'm not very good at Erlang syntax, but hopefully it makes sense:

pid = spawn(fn -> true end) # spawn a process that immediately dies
Process.sleep(100) # give it a moment to finish
:recon.info(pid, [:binary_memory])

** (FunctionClauseError) no function clause matching in :recon.proc_fake/2

    The following arguments were given to :recon.proc_fake/2:

        # 1
        [:binary_memory]

        # 2
        :undefined

    (recon 2.5.2) src/recon.erl:247: :recon.proc_fake/2

[digitalcora]

We recently tried to remove our workaround for this issue, but it appears to still exist in the current version 2.5.6 — the repro I posted above results in exactly the same internal crash (source line, which was not changed in #97).

[ferd]

See if #115 works; I'm sorry I couldn't get to this better, it was a straightforward fix and the test should be robust enough.

[digitalcora]

Thanks @ferd, from our testing so far this issue seems fixed, as long as we handle the possible undefined.