Prevent MinGW builds on Windows from relying on a non-exported symbol for "_PyGen_Send".

Closes #1968.

CHANGES.rst

@@ -14,6 +14,9 @@ Bugs fixed
 * NumPy slicing generated incorrect results when compiled with Pythran.
   (Github issue #1946)
 
+* Fix "undefined reference" linker error for generators on Windows in Py3.3-3.5.
+  (Github issue #1968)
+
 * Adapt to recent C-API change of ``PyThreadState`` in CPython 3.7.
 
 

Cython/Utility/Coroutine.c

@@ -783,13 +783,13 @@ static PyObject *__Pyx_Coroutine_Send(PyObject *self, PyObject *value) {
             ret = __Pyx_async_gen_asend_send(yf, value);
         } else
         #endif
-        #if CYTHON_COMPILING_IN_CPYTHON && PY_VERSION_HEX >= 0x03030000 && (!defined(_MSC_VER) || PY_VERSION_HEX >= 0x03060000)
+        #if CYTHON_COMPILING_IN_CPYTHON && PY_VERSION_HEX >= 0x03030000 && (defined(__linux__) || PY_VERSION_HEX >= 0x030600B3)
         // _PyGen_Send() is not exported before Py3.6
         if (PyGen_CheckExact(yf)) {
             ret = _PyGen_Send((PyGenObject*)yf, value == Py_None ? NULL : value);
         } else
         #endif
-        #if CYTHON_COMPILING_IN_CPYTHON && PY_VERSION_HEX >= 0x03050000 && defined(PyCoro_CheckExact) && (!defined(_MSC_VER) || PY_VERSION_HEX >= 0x03060000)
+        #if CYTHON_COMPILING_IN_CPYTHON && PY_VERSION_HEX >= 0x03050000 && defined(PyCoro_CheckExact) && (defined(__linux__) || PY_VERSION_HEX >= 0x030600B3)
         // _PyGen_Send() is not exported before Py3.6
         if (PyCoro_CheckExact(yf)) {
             ret = _PyGen_Send((PyGenObject*)yf, value == Py_None ? NULL : value);
@@ -885,7 +885,7 @@ static PyObject *__Pyx_Generator_Next(PyObject *self) {
             ret = __Pyx_Generator_Next(yf);
         } else
         #endif
-        #if CYTHON_COMPILING_IN_CPYTHON && PY_VERSION_HEX >= 0x03030000 && (!defined(_MSC_VER) || PY_VERSION_HEX >= 0x03060000)
+        #if CYTHON_COMPILING_IN_CPYTHON && PY_VERSION_HEX >= 0x03030000 && (defined(__linux__) || PY_VERSION_HEX >= 0x030600B3)
         // _PyGen_Send() is not exported before Py3.6
         if (PyGen_CheckExact(yf)) {
             ret = _PyGen_Send((PyGenObject*)yf, NULL);