Compiler module leak on file/module level compilation error

[lukaszsamson]

Elixir and Erlang/OTP versions

Erlang/OTP 28 [erts-16.2] [source] [64-bit] [smp:12:12] [ds:12:12:10] [async-threads:1] [jit]

Elixir 1.20.0-rc.4 (116f8f4) (compiled with Erlang/OTP 28)

Operating system

any

Current behavior

Repro in iex:

Code.compile_string("raise \"boom\"")
** (RuntimeError) boom
    nofile:1: (file)
    (elixir 1.20.0-rc.4) src/elixir_compiler.erl:101: :elixir_compiler.dispatch/4
    (elixir 1.20.0-rc.4) src/elixir_compiler.erl:76: :elixir_compiler.compile/4
    (elixir 1.20.0-rc.4) src/elixir_compiler.erl:42: :elixir_compiler.optimize_defmodule/2
    (elixir 1.20.0-rc.4) src/elixir_lexical.erl:18: :elixir_lexical.run/3
    (elixir 1.20.0-rc.4) src/elixir_compiler.erl:21: :elixir_compiler.quoted/3
    iex:1: (file)
iex(1)> IO.inspect(:sys.get_state(:elixir_code_server))
{:elixir_code_server, %{}, {[], [], 1}, %{}}

Code.compile_string("raise \"boom\"")
** (RuntimeError) boom
    nofile:1: (file)
    (elixir 1.20.0-rc.4) src/elixir_compiler.erl:101: :elixir_compiler.dispatch/4
    (elixir 1.20.0-rc.4) src/elixir_compiler.erl:76: :elixir_compiler.compile/4
    (elixir 1.20.0-rc.4) src/elixir_compiler.erl:42: :elixir_compiler.optimize_defmodule/2
    (elixir 1.20.0-rc.4) src/elixir_lexical.erl:18: :elixir_lexical.run/3
    (elixir 1.20.0-rc.4) src/elixir_compiler.erl:21: :elixir_compiler.quoted/3
    iex:2: (file)
iex(2)> IO.inspect(:sys.get_state(:elixir_code_server))
{:elixir_code_server, %{}, {[], [], 2}, %{}}

:code.all_loaded() |> Enum.filter(& elem(&1, 0) |> to_string |> String.starts_with?("elixir_compiler_"))
[elixir_compiler_1: [], elixir_compiler_0: []]

Code.purge_compiler_modules()
{:ok, 0}

:code.all_loaded() |> Enum.filter(& elem(&1, 0) |> to_string |> String.starts_with?("elixir_compiler_"))
[elixir_compiler_1: [], elixir_compiler_0: []]

Notice the counter gets incremented but modules are not registered in code server state. They stay loaded and is not purgeable by Code.purge_compiler_modules/0

The same happens if the crash is in module body

Code.compile_string("defmodule Foo do\n raise \"boom\"\nend")

Likely reason:
When Module:Fun(Args) in dispatch crashes return_compiler_module is not called

elixir/lib/elixir/src/elixir_compiler.erl

Lines 100 to 103 in a37db60

	dispatch(Module, Fun, Args, Purgeable) ->
	Res = Module:Fun(Args),
	return_compiler_module(Module, Purgeable),
	Res.

Expected behavior

Two alternatives

1. Failed modules should be accounted for in code server state and purgeable
2. Should be purged right away

[josevalim]

Good find! Please send a PR :)