Tweak the way libuv stops handles after a callback.

Fixes #1564.

docs/changes/1564.bugfix

+Fix a spurious warning about watchers and resource leaks on libuv on
+Windows. Reported by Stéphane Rainville.

pyproject.toml

@@ -26,6 +26,6 @@ directory = "docs/changes"
 filename = "CHANGES.rst"
 package = "gevent"
 package_dir = "src"
-issue_format = ":issue:`{issue}`"
+issue_format = "See :issue:`{issue}`."
 title_format = false
 template = "docs/_templates/hr-between-versions.rst.tmpl"

src/gevent/__init__.py

@@ -21,7 +21,7 @@ _version_info = namedtuple('version_info',
 #: .. deprecated:: 1.2
 #:  Use ``pkg_resources.parse_version(__version__)`` (or the equivalent
 #:  ``packaging.version.Version(__version__)``).
-version_info = _version_info(1, 5, 0, 'dev', 0)
+version_info = _version_info(20, 0, 0, 'dev', 0) # XXX: Remove me
 
 #: The human-readable PEP 440 version identifier.
 #: Use ``pkg_resources.parse_version(__version__)`` or

src/gevent/_ffi/loop.py

@@ -310,17 +310,28 @@ class AbstractCallbacks(object):
 
 
 def assign_standard_callbacks(ffi, lib, callbacks_class, extras=()): # pylint:disable=unused-argument
+    """
+    Given the typical *ffi* and *lib* arguments, and a subclass of :class:`AbstractCallbacks`
+    in *callbacks_class*, set up the ``def_extern`` Python callbacks from C
+    into an instance of *callbacks_class*.
+
+    :param tuple extras: If given, this is a sequence of ``(name, error_function)``
+      additional callbacks to register. Each *name* is an attribute of
+      the *callbacks_class* instance. (Each element cas also be just a *name*.)
+    :return: The *callbacks_class* instance. This object must be kept alive,
+      typically at module scope.
+    """
     # callbacks keeps these cdata objects alive at the python level
     callbacks = callbacks_class(ffi)
     extras = [extra if len(extra) == 2 else (extra, None) for extra in extras]
     extras = tuple([(getattr(callbacks, name), error) for name, error in extras])
-    for (func, error_func) in ((callbacks.python_callback, None),
-                               (callbacks.python_handle_error, None),
-                               (callbacks.python_stop, None),
-                               (callbacks.python_check_callback,
-                                callbacks.check_callback_onerror),
-                               (callbacks.python_prepare_callback,
-                                callbacks.check_callback_onerror)) + extras:
+    for (func, error_func) in (
+            (callbacks.python_callback, None),
+            (callbacks.python_handle_error, None),
+            (callbacks.python_stop, None),
+            (callbacks.python_check_callback, callbacks.check_callback_onerror),
+            (callbacks.python_prepare_callback, callbacks.check_callback_onerror)
+    ) + extras:
         # The name of the callback function matches the 'extern Python' declaration.
         error_func = error_func or callbacks.unhandled_onerror
         callback = ffi.def_extern(onerror=error_func)(func)

src/gevent/libuv/loop.py

@@ -448,8 +448,8 @@ class loop(AbstractLoop):
         if not self._queued_callbacks:
             return False
 
-        cbs = list(self._queued_callbacks)
-        self._queued_callbacks = []
+        cbs = self._queued_callbacks[:]
+        del self._queued_callbacks[:]
 
         for watcher_ptr, arg in cbs:
             handle = watcher_ptr.data
@@ -458,15 +458,23 @@ class loop(AbstractLoop):
                 assert not libuv.uv_is_active(watcher_ptr)
                 continue
             val = _callbacks.python_callback(handle, arg)
-            if val == -1:
+            if val == -1: # Failure.
                 _callbacks.python_handle_error(handle, arg)
-            elif val == 1:
+            elif val == 1: # Success
                 if not libuv.uv_is_active(watcher_ptr):
-                    if watcher_ptr.data != handle:
-                        if watcher_ptr.data:
-                            _callbacks.python_stop(None)
-                    else:
-                        _callbacks.python_stop(handle)
+                    # The callback closed the watcher in C. Good.
+                    # It's supposed to also reset the pointer to NULL at
+                    # that same time. If it resets it to something else, we're
+                    # re-using the same watcher object, and that's not correct either.
+                    # Prevoiusly we checked for that case, but we shouldn't need to.
+                    handle_after_callback = watcher_ptr.data
+                    try:
+                        if handle_after_callback:
+                            _callbacks.python_stop(handle_after_callback)
+                        if handle_after_callback != handle:
+                            _callbacks.python_stop(handle)
+                    finally:
+                        watcher_ptr.data = ffi.NULL
         return True
 
 

src/gevent/libuv/watcher.py

@@ -125,7 +125,7 @@ class watcher(_base.watcher):
         # Instead, this is arranged as a callback to GC when the
         # watcher class dies. Obviously it's important to keep the ffi
         # watcher alive.
-        # We can pass in "subclasses" if uv_handle_t that line up at the C level,
+        # We can pass in "subclasses" of uv_handle_t that line up at the C level,
         # but that don't in CFFI without a cast. But be careful what we use the cast
         # for, don't pass it back to C.
         ffi_handle_watcher = cls._FFI.cast('uv_handle_t*', ffi_watcher)

src/gevent/resolver/dnshelper.c

@@ -13,10 +13,11 @@
 #include "cares_ntop.h"
 #include "cares_pton.h"
 
-#if PY_VERSION_HEX < 0x02060000
-  #define PyUnicode_FromString         PyString_FromString
-#elif PY_MAJOR_VERSION < 3
-  #define PyUnicode_FromString         PyBytes_FromString
+#if PY_MAJOR_VERSION >= 3
+#define PY3K
+#define GPyNative_FromString PyUnicode_FromString
+#else
+#define GPyNative_FromString PyString_FromString
 #endif
 
 
@@ -51,7 +52,7 @@ gevent_append_addr(PyObject* list, int family, void* src, char* tmpbuf, size_t t
     int status = -1;
     PyObject* tmp;
     if (ares_inet_ntop(family, src, tmpbuf, tmpsize)) {
-        tmp = PyUnicode_FromString(tmpbuf);
+        tmp = GPyNative_FromString(tmpbuf);
         if (tmp) {
             status = PyList_Append(list, tmp);
             Py_DECREF(tmp);
@@ -64,7 +65,7 @@ gevent_append_addr(PyObject* list, int family, void* src, char* tmpbuf, size_t t
 static PyObject*
 parse_h_name(struct hostent *h)
 {
-    return PyUnicode_FromString(h->h_name);
+    return GPyNative_FromString(h->h_name);
 }
 
 
@@ -81,7 +82,7 @@ parse_h_aliases(struct hostent *h)
         for (pch = h->h_aliases; *pch != NULL; pch++) {
             if (*pch != h->h_name && strcmp(*pch, h->h_name)) {
                 int status;
-                tmp = PyUnicode_FromString(*pch);
+                tmp = GPyNative_FromString(*pch);
                 if (tmp == NULL) {
                     break;
                 }