Elixir library: fix crash with inspect(:atom)

inspect was returning a list instead of a binary.
Also fix handling of atom special cases.

Signed-off-by: Davide Bettio <davide@uninstall.it>

Author: bettio

CHANGELOG.md

@@ -38,6 +38,7 @@ instead
 - Fix memory corruption in `unicode:characters_to_binary`
 - Fix handling of large literal indexes
 - `unicode:characters_to_list`: fixed bogus out_of_memory error on some platforms such as ESP32
+- Fix crash in Elixir library when doing `inspect(:atom)`
 
 ## [0.6.4] - 2024-08-18
 

libs/exavmlib/lib/Kernel.ex

@@ -42,7 +42,7 @@ defmodule Kernel do
   def inspect(term, opts \\ []) when is_list(opts) do
     case term do
       t when is_atom(t) ->
-        [?:, atom_to_string(t)]
+        atom_to_string(t, ":")
 
       t when is_integer(t) ->
         :erlang.integer_to_binary(t)
@@ -118,10 +118,26 @@ defmodule Kernel do
     )
   end
 
-  defp atom_to_string(atom) do
-    # TODO: use unicode rather than plain latin1
-    # handle spaces and special characters
-    :erlang.atom_to_binary(atom, :latin1)
+  defp atom_to_string(atom, prefix \\ "") do
+    case atom do
+      true ->
+        "true"
+
+      false ->
+        "false"
+
+      nil ->
+        "nil"
+
+      any_atom ->
+        case :erlang.atom_to_binary(any_atom) do
+          <<"Elixir.", displayable::binary>> ->
+            displayable
+
+          other ->
+            <<prefix::binary, other::binary>>
+        end
+    end
   end
 
   @doc """

tests/libs/exavmlib/Tests.ex

@@ -26,6 +26,7 @@ defmodule Tests do
     :ok = test_enum()
     :ok = test_exception()
     :ok = test_chars_protocol()
+    :ok = test_inspect()
     :ok = IO.puts("Finished Elixir tests")
   end
 
@@ -234,6 +235,18 @@ defmodule Tests do
     :ok
   end
 
+  def test_inspect() do
+    "true" = inspect(true)
+    "false" = inspect(false)
+    "nil" = inspect(nil)
+
+    ":test" = inspect(:test)
+    ":アトム" = inspect(:アトム)
+    "Test" = inspect(Test)
+
+    :ok
+  end
+
   defp fact(n) when n < 0, do: :test
   defp fact(0), do: 1
   defp fact(n), do: fact(n - 1) * n