bpo-30555: Fix WindowsConsoleIO fails in the presence of fd redirecti…

…on (GH-1927)

This works by not caching the handle and instead getting the handle from
the file descriptor each time, so that if the actual handle changes by
fd redirection closing/opening the console handle beneath our feet, we
will keep working correctly.

Include/cpython/fileutils.h

@@ -161,4 +161,12 @@ PyAPI_FUNC(int) _Py_dup(int fd);
 PyAPI_FUNC(int) _Py_get_blocking(int fd);
 
 PyAPI_FUNC(int) _Py_set_blocking(int fd, int blocking);
-#endif   /* !MS_WINDOWS */
+#else   /* MS_WINDOWS */
+PyAPI_FUNC(void*) _Py_get_osfhandle_noraise(int fd);
+
+PyAPI_FUNC(void*) _Py_get_osfhandle(int fd);
+
+PyAPI_FUNC(int) _Py_open_osfhandle_noraise(void *handle, int flags);
+
+PyAPI_FUNC(int) _Py_open_osfhandle(void *handle, int flags);
+#endif  /* MS_WINDOWS */

Misc/NEWS.d/next/Windows/2017-12-16-12-23-51.bpo-30555.3ybjly.rst

@@ -0,0 +1,2 @@
+Fix ``WindowsConsoleIO`` errors in the presence of fd redirection. Patch by
+Segev Finer.

Modules/_io/clinic/winconsoleio.c.h

@@ -8,10 +8,10 @@ PyDoc_STRVAR(_io__WindowsConsoleIO_close__doc__,
 "close($self, /)\n"
 "--\n"
 "\n"
-"Close the handle.\n"
+"Close the console object.\n"
 "\n"
-"A closed handle cannot be used for further I/O operations.  close() may be\n"
-"called more than once without error.");
+"A closed console object cannot be used for further I/O operations.\n"
+"close() may be called more than once without error.");
 
 #define _IO__WINDOWSCONSOLEIO_CLOSE_METHODDEF    \
     {"close", (PyCFunction)_io__WindowsConsoleIO_close, METH_NOARGS, _io__WindowsConsoleIO_close__doc__},
@@ -110,10 +110,7 @@ PyDoc_STRVAR(_io__WindowsConsoleIO_fileno__doc__,
 "fileno($self, /)\n"
 "--\n"
 "\n"
-"Return the underlying file descriptor (an integer).\n"
-"\n"
-"fileno is only set when a file descriptor is used to open\n"
-"one of the standard streams.");
+"Return the underlying file descriptor (an integer).");
 
 #define _IO__WINDOWSCONSOLEIO_FILENO_METHODDEF    \
     {"fileno", (PyCFunction)_io__WindowsConsoleIO_fileno, METH_NOARGS, _io__WindowsConsoleIO_fileno__doc__},
@@ -381,4 +378,4 @@ _io__WindowsConsoleIO_isatty(winconsoleio *self, PyObject *Py_UNUSED(ignored))
 #ifndef _IO__WINDOWSCONSOLEIO_ISATTY_METHODDEF
     #define _IO__WINDOWSCONSOLEIO_ISATTY_METHODDEF
 #endif /* !defined(_IO__WINDOWSCONSOLEIO_ISATTY_METHODDEF) */
-/*[clinic end generated code: output=a28b3120fa53b256 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=48080572ffee22f5 input=a9049054013a1b77]*/