For the last few weeks I was working on purity and effects analyzer of Elixir and Erlang projects, and I came across a bunch of interesting functions which were built-in but undocumented or hidden.
Please, do not use them in production systems because they’re a subject to change
But don’t hesitate to play with them to check how the erlang runtime works, or make some dark magic there
:erts_internal.cmp_termcompares two terms in oldschool
:erts_internal.term_type, function which returns a top-level type of the structure. Interesting thing is that for
:atom. This function is really useful for debugging of binaries
:erts_internal.map_to_tuple_keysto show keys tuple for flatmaps (maps with <= 32 keys)
:erts_internal.map_hashmap_childrento show the Tree representation of the hashmap (map with > 32 keys)
:erts_internal.ets_super_userto make the current process become a ETS process with maximum privileges. Process will have read/write access to any ets table (even protected and private ones)
:binary.referenced_byte_size(documented) to check a size of a referenced binary
:prim_eval.recevewhich works like a normal
receive, but allows to decide whether to pick or not to pick the message from the queue to the closure rather then a pattern. It allows to peek in the head of the queue, without taking the value out of queue
try do: :prim_eval.receive(fn x -> throw(x) end, 0), catch: (x -> x)
:erts_debug.sameto check if the values are represented by the exactly same structure in memory (this means that pointers for heap values are equal)
:erts_debug.flat_sizeto check the size with term reusage and flat size like if every term was referenced only once.
If you know any other magic functions, please post them in this thread