Enable explicit destruction of all resources (#209)

* Enable explicit destruction of all resources

This commit adds a suite of methods to most of the types in this package
to enable explicit destruction of resources as necessary. Specifically
most classes which own a pointer internally now sport some new methods:

* `__enter__` and `__exit__` enable using the objects in `with` blocks.
* `close` enables explicitly deallocating the object.

All objects internally now validate that they have not been closed
before operating, raising a `ValueError` if a closed object is operated
on.

* Try to appease Python 3.8

tests/test_config.py

@@ -1,4 +1,5 @@
 import unittest
+from contextlib import closing
 
 from wasmtime import *
 
@@ -34,3 +35,14 @@ def test_smoke(self):
         config.consume_fuel = True
         config.wasm_relaxed_simd = True
         config.wasm_relaxed_simd_deterministic = True
+
+        with closing(config) as config:
+            pass
+
+        config.close()
+
+        with self.assertRaises(ValueError):
+            Engine(config)
+
+        with self.assertRaises(ValueError):
+            config.cache = True

tests/test_engine.py

@@ -13,5 +13,5 @@ def test_errors(self):
             Engine(3)  # type: ignore
         config = Config()
         Engine(config)
-        with self.assertRaises(WasmtimeError):
+        with self.assertRaises(ValueError):
             Engine(config)

tests/test_store.py

@@ -8,6 +8,15 @@ def test_smoke(self):
         Store()
         Store(Engine())
 
+        with Store() as store:
+            pass
+
+        store = Store()
+        store.close()
+        store.close()
+        with self.assertRaises(ValueError):
+            store.set_epoch_deadline(1)
+
     def test_errors(self):
         with self.assertRaises(TypeError):
             Store(3)  # type: ignore

wasmtime/__init__.py

@@ -13,6 +13,7 @@
 libraries are intended to be quite similar.
 """
 
+from ._managed import Managed
 from ._error import WasmtimeError, ExitTrap
 from ._config import Config
 from ._engine import Engine

wasmtime/_config.py

@@ -1,7 +1,7 @@
 from . import _ffi as ffi
 from ctypes import *
 import ctypes
-from wasmtime import WasmtimeError
+from wasmtime import WasmtimeError, Managed
 import typing
 
 
@@ -13,18 +13,19 @@ def setter_property(fset: typing.Callable) -> property:
     return prop
 
 
-class Config:
+class Config(Managed["ctypes._Pointer[ffi.wasm_config_t]"]):
     """
     Global configuration, used to create an `Engine`.
 
     A `Config` houses a number of configuration options which tweaks how wasm
     code is compiled or generated.
     """
 
-    _ptr: "ctypes._Pointer[ffi.wasm_config_t]"
-
     def __init__(self) -> None:
-        self._ptr = ffi.wasm_config_new()
+        self._set_ptr(ffi.wasm_config_new())
+
+    def _delete(self, ptr: "ctypes._Pointer[ffi.wasm_config_t]") -> None:
+        ffi.wasm_config_delete(ptr)
 
     @setter_property
     def debug_info(self, enable: bool) -> None:
@@ -35,7 +36,7 @@ def debug_info(self, enable: bool) -> None:
 
         if not isinstance(enable, bool):
             raise TypeError('expected a bool')
-        ffi.wasmtime_config_debug_info_set(self._ptr, enable)
+        ffi.wasmtime_config_debug_info_set(self.ptr(), enable)
 
     @setter_property
     def wasm_threads(self, enable: bool) -> None:
@@ -47,7 +48,7 @@ def wasm_threads(self, enable: bool) -> None:
 
         if not isinstance(enable, bool):
             raise TypeError('expected a bool')
-        ffi.wasmtime_config_wasm_threads_set(self._ptr, enable)
+        ffi.wasmtime_config_wasm_threads_set(self.ptr(), enable)
 
     @setter_property
     def wasm_reference_types(self, enable: bool) -> None:
@@ -59,7 +60,7 @@ def wasm_reference_types(self, enable: bool) -> None:
 
         if not isinstance(enable, bool):
             raise TypeError('expected a bool')
-        ffi.wasmtime_config_wasm_reference_types_set(self._ptr, enable)
+        ffi.wasmtime_config_wasm_reference_types_set(self.ptr(), enable)
 
     @setter_property
     def wasm_simd(self, enable: bool) -> None:
@@ -71,7 +72,7 @@ def wasm_simd(self, enable: bool) -> None:
 
         if not isinstance(enable, bool):
             raise TypeError('expected a bool')
-        ffi.wasmtime_config_wasm_simd_set(self._ptr, enable)
+        ffi.wasmtime_config_wasm_simd_set(self.ptr(), enable)
 
     @setter_property
     def wasm_bulk_memory(self, enable: bool) -> None:
@@ -83,7 +84,7 @@ def wasm_bulk_memory(self, enable: bool) -> None:
 
         if not isinstance(enable, bool):
             raise TypeError('expected a bool')
-        ffi.wasmtime_config_wasm_bulk_memory_set(self._ptr, enable)
+        ffi.wasmtime_config_wasm_bulk_memory_set(self.ptr(), enable)
 
     @setter_property
     def wasm_multi_value(self, enable: bool) -> None:
@@ -95,7 +96,7 @@ def wasm_multi_value(self, enable: bool) -> None:
 
         if not isinstance(enable, bool):
             raise TypeError('expected a bool')
-        ffi.wasmtime_config_wasm_multi_value_set(self._ptr, enable)
+        ffi.wasmtime_config_wasm_multi_value_set(self.ptr(), enable)
 
     @setter_property
     def wasm_multi_memory(self, enable: bool) -> None:
@@ -107,7 +108,7 @@ def wasm_multi_memory(self, enable: bool) -> None:
 
         if not isinstance(enable, bool):
             raise TypeError('expected a bool')
-        ffi.wasmtime_config_wasm_multi_memory_set(self._ptr, enable)
+        ffi.wasmtime_config_wasm_multi_memory_set(self.ptr(), enable)
 
     @setter_property
     def wasm_memory64(self, enable: bool) -> None:
@@ -119,7 +120,7 @@ def wasm_memory64(self, enable: bool) -> None:
 
         if not isinstance(enable, bool):
             raise TypeError('expected a bool')
-        ffi.wasmtime_config_wasm_memory64_set(self._ptr, enable)
+        ffi.wasmtime_config_wasm_memory64_set(self.ptr(), enable)
 
     @setter_property
     def wasm_relaxed_simd(self, enable: bool) -> None:
@@ -131,7 +132,7 @@ def wasm_relaxed_simd(self, enable: bool) -> None:
 
         if not isinstance(enable, bool):
             raise TypeError('expected a bool')
-        ffi.wasmtime_config_wasm_relaxed_simd_set(self._ptr, enable)
+        ffi.wasmtime_config_wasm_relaxed_simd_set(self.ptr(), enable)
 
     @setter_property
     def wasm_relaxed_simd_deterministic(self, enable: bool) -> None:
@@ -145,7 +146,7 @@ def wasm_relaxed_simd_deterministic(self, enable: bool) -> None:
 
         if not isinstance(enable, bool):
             raise TypeError('expected a bool')
-        ffi.wasmtime_config_wasm_relaxed_simd_deterministic_set(self._ptr, enable)
+        ffi.wasmtime_config_wasm_relaxed_simd_deterministic_set(self.ptr(), enable)
 
     @setter_property
     def strategy(self, strategy: str) -> None:
@@ -159,35 +160,35 @@ def strategy(self, strategy: str) -> None:
         """
 
         if strategy == "auto":
-            ffi.wasmtime_config_strategy_set(self._ptr, 0)
+            ffi.wasmtime_config_strategy_set(self.ptr(), 0)
         elif strategy == "cranelift":
-            ffi.wasmtime_config_strategy_set(self._ptr, 1)
+            ffi.wasmtime_config_strategy_set(self.ptr(), 1)
         else:
             raise WasmtimeError("unknown strategy: " + str(strategy))
 
     @setter_property
     def cranelift_debug_verifier(self, enable: bool) -> None:
         if not isinstance(enable, bool):
             raise TypeError('expected a bool')
-        ffi.wasmtime_config_cranelift_debug_verifier_set(self._ptr, enable)
+        ffi.wasmtime_config_cranelift_debug_verifier_set(self.ptr(), enable)
 
     @setter_property
     def cranelift_opt_level(self, opt_level: str) -> None:
         if opt_level == "none":
-            ffi.wasmtime_config_cranelift_opt_level_set(self._ptr, 0)
+            ffi.wasmtime_config_cranelift_opt_level_set(self.ptr(), 0)
         elif opt_level == "speed":
-            ffi.wasmtime_config_cranelift_opt_level_set(self._ptr, 1)
+            ffi.wasmtime_config_cranelift_opt_level_set(self.ptr(), 1)
         elif opt_level == "speed_and_size":
-            ffi.wasmtime_config_cranelift_opt_level_set(self._ptr, 2)
+            ffi.wasmtime_config_cranelift_opt_level_set(self.ptr(), 2)
         else:
             raise WasmtimeError("unknown opt level: " + str(opt_level))
 
     @setter_property
     def profiler(self, profiler: str) -> None:
         if profiler == "none":
-            ffi.wasmtime_config_profiler_set(self._ptr, 0)
+            ffi.wasmtime_config_profiler_set(self.ptr(), 0)
         elif profiler == "jitdump":
-            ffi.wasmtime_config_profiler_set(self._ptr, 1)
+            ffi.wasmtime_config_profiler_set(self.ptr(), 1)
         else:
             raise WasmtimeError("unknown profiler: " + str(profiler))
 
@@ -207,9 +208,9 @@ def cache(self, enabled: typing.Union[bool, str]) -> None:
         if isinstance(enabled, bool):
             if not enabled:
                 raise WasmtimeError("caching cannot be explicitly disabled")
-            error = ffi.wasmtime_config_cache_config_load(self._ptr, None)
+            error = ffi.wasmtime_config_cache_config_load(self.ptr(), None)
         elif isinstance(enabled, str):
-            error = ffi.wasmtime_config_cache_config_load(self._ptr,
+            error = ffi.wasmtime_config_cache_config_load(self.ptr(),
                                                           c_char_p(enabled.encode('utf-8')))
         else:
             raise TypeError("expected string or bool")
@@ -227,7 +228,7 @@ def epoch_interruption(self, enabled: bool) -> None:
             val = 1
         else:
             val = 0
-        ffi.wasmtime_config_epoch_interruption_set(self._ptr, val)
+        ffi.wasmtime_config_epoch_interruption_set(self.ptr(), val)
 
     @setter_property
     def consume_fuel(self, instances: bool) -> None:
@@ -240,7 +241,7 @@ def consume_fuel(self, instances: bool) -> None:
         """
         if not isinstance(instances, bool):
             raise TypeError('expected an bool')
-        ffi.wasmtime_config_consume_fuel_set(self._ptr, instances)
+        ffi.wasmtime_config_consume_fuel_set(self.ptr(), instances)
 
     @setter_property
     def parallel_compilation(self, enable: bool) -> None:
@@ -252,8 +253,4 @@ def parallel_compilation(self, enable: bool) -> None:
         """
         if not isinstance(enable, bool):
             raise TypeError('expected a bool')
-        ffi.wasmtime_config_parallel_compilation_set(self._ptr, enable)
-
-    def __del__(self) -> None:
-        if hasattr(self, '_ptr'):
-            ffi.wasm_config_delete(self._ptr)
+        ffi.wasmtime_config_parallel_compilation_set(self.ptr(), enable)

wasmtime/_engine.py

@@ -1,27 +1,22 @@
 from . import _ffi as ffi
-from wasmtime import Config, WasmtimeError
+from wasmtime import Config, WasmtimeError, Managed
 from typing import Optional
 import ctypes
 
 
-class Engine:
-    _ptr: "ctypes._Pointer[ffi.wasm_engine_t]"
+class Engine(Managed["ctypes._Pointer[ffi.wasm_engine_t]"]):
 
     def __init__(self, config: Optional[Config] = None):
         if config is None:
-            self._ptr = ffi.wasm_engine_new()
+            self._set_ptr(ffi.wasm_engine_new())
         elif not isinstance(config, Config):
             raise TypeError("expected Config")
-        elif not hasattr(config, '_ptr'):
-            raise WasmtimeError("Config already used")
         else:
-            ptr = config._ptr
-            delattr(config, '_ptr')
-            self._ptr = ffi.wasm_engine_new_with_config(ptr)
+            ptr = config._consume()
+            self._set_ptr(ffi.wasm_engine_new_with_config(ptr))
 
-    def increment_epoch(self) -> None:
-        ffi.wasmtime_engine_increment_epoch(self._ptr)
+    def _delete(self, ptr: "ctypes._Pointer[ffi.wasm_engine_t]") -> None:
+        ffi.wasm_engine_delete(ptr)
 
-    def __del__(self) -> None:
-        if hasattr(self, '_ptr'):
-            ffi.wasm_engine_delete(self._ptr)
+    def increment_epoch(self) -> None:
+        ffi.wasmtime_engine_increment_epoch(self.ptr())

wasmtime/_error.py

@@ -2,15 +2,17 @@
 from . import _ffi as ffi
 import ctypes
 from typing import Optional
+from wasmtime import Managed
 
 
-class WasmtimeError(Exception):
-    _ptr: "Optional[ctypes._Pointer[ffi.wasmtime_error_t]]"
-    _message: Optional[str]
+class WasmtimeError(Exception, Managed["ctypes._Pointer[ffi.wasmtime_error_t]"]):
+    __message: Optional[str]
 
     def __init__(self, message: str):
-        self._message = message
-        self._ptr = None
+        self.__message = message
+
+    def _delete(self, ptr: "ctypes._Pointer[ffi.wasmtime_error_t]") -> None:
+        ffi.wasmtime_error_delete(ptr)
 
     @classmethod
     def _from_ptr(cls, ptr: "ctypes._Pointer") -> 'WasmtimeError':
@@ -21,29 +23,25 @@ def _from_ptr(cls, ptr: "ctypes._Pointer") -> 'WasmtimeError':
         exit_code = c_int(0)
         if ffi.wasmtime_error_exit_status(ptr, byref(exit_code)):
             exit_trap: ExitTrap = ExitTrap.__new__(ExitTrap)
-            exit_trap._ptr = ptr
-            exit_trap._message = None
+            exit_trap._set_ptr(ptr)
+            exit_trap.__message = None
             exit_trap.code = exit_code.value
             return exit_trap
 
         err: WasmtimeError = cls.__new__(cls)
-        err._ptr = ptr
-        err._message = None
+        err._set_ptr(ptr)
+        err.__message = None
         return err
 
     def __str__(self) -> str:
-        if self._message:
-            return self._message
+        if self.__message:
+            return self.__message
         message_vec = ffi.wasm_byte_vec_t()
-        ffi.wasmtime_error_message(self._ptr, byref(message_vec))
+        ffi.wasmtime_error_message(self.ptr(), byref(message_vec))
         message = ffi.to_str(message_vec)
         ffi.wasm_byte_vec_delete(byref(message_vec))
         return message
 
-    def __del__(self) -> None:
-        if hasattr(self, '_ptr') and self._ptr:
-            ffi.wasmtime_error_delete(self._ptr)
-
 
 class ExitTrap(WasmtimeError):
     """

wasmtime/_extern.py

@@ -1,7 +1,7 @@
 from . import _ffi as ffi
 import ctypes
 from ._exportable import AsExtern
-from wasmtime import WasmtimeError
+from wasmtime import WasmtimeError, Managed
 
 
 def wrap_extern(ptr: ffi.wasmtime_extern_t) -> AsExtern:
@@ -41,9 +41,9 @@ def get_extern_ptr(item: AsExtern) -> ffi.wasmtime_extern_t:
         raise TypeError("expected a Func, Global, Memory, Table, Module, or Instance")
 
 
-class Extern:
+class Extern(Managed["ctypes._Pointer[ffi.wasm_extern_t]"]):
     def __init__(self, ptr: "ctypes._Pointer[ffi.wasm_extern_t]"):
-        self.ptr = ptr
+        self._set_ptr(ptr)
 
-    def __del__(self) -> None:
-        ffi.wasm_extern_delete(self.ptr)
+    def _delete(self, ptr: "ctypes._Pointer[ffi.wasm_extern_t]") -> None:
+        ffi.wasm_extern_delete(ptr)