Patch 1329 (partial) by Christian Heimes.

Add a closefd flag to open() which can be set to False to prevent closing
the file descriptor when close() is called or when the object is destroyed.
Useful to ensure that sys.std{in,out,err} keep their file descriptors open
when Python is uninitialized.  (This was always a feature in 2.x, it just
wasn't implemented in 3.0 yet.)

10 files changed, 63 insertions, 31 deletions

diff --git a/Doc/c-api/concrete.rst b/Doc/c-api/concrete.rst
index cdea26f1bc..1e1fa0dccf 100644
--- a/Doc/c-api/concrete.rst
+++ b/Doc/c-api/concrete.rst
@@ -2401,12 +2401,12 @@ change in future releases of Python.
    :ctype:`PyFileObject`.
 
 
-.. cfunction:: PyFile_FromFd(int fd, char *name, char *mode, int buffering, char *encoding, char *newline)
+.. cfunction:: PyFile_FromFd(int fd, char *name, char *mode, int buffering, char *encoding, char *newline, int closefd)
 
    Create a new :ctype:`PyFileObject` from the file descriptor of an already
    opened file *fd*. The arguments *name*, *encoding* and *newline* can be
-   *NULL* as well as buffering can be *-1* to use the defaults. Return *NULL* on
-   failure.
+   *NULL* to use the defaults; *buffering* can be *-1* to use the default.
+   Return *NULL* on failure.
 
    .. warning::
 
diff --git a/Include/fileobject.h b/Include/fileobject.h
index acb8c6ddc1..ae127da0c7 100644
--- a/Include/fileobject.h
+++ b/Include/fileobject.h
@@ -8,7 +8,8 @@ extern "C" {
 
 #define PY_STDIOTEXTMODE "b"
 
-PyAPI_FUNC(PyObject *) PyFile_FromFd(int, char *, char *, int, char *, char *);
+PyAPI_FUNC(PyObject *) PyFile_FromFd(int, char *, char *, int, char *, char *,
+				     int);
 PyAPI_FUNC(PyObject *) PyFile_GetLine(PyObject *, int);
 PyAPI_FUNC(int) PyFile_WriteObject(PyObject *, PyObject *, int);
 PyAPI_FUNC(int) PyFile_WriteString(const char *, PyObject *);
diff --git a/Lib/io.py b/Lib/io.py
index c2d803ccfe..d7709c4594 100644
--- a/Lib/io.py
+++ b/Lib/io.py
@@ -49,7 +49,8 @@ class BlockingIOError(IOError):
         self.characters_written = characters_written
 
 
-def open(file, mode="r", buffering=None, encoding=None, newline=None):
+def open(file, mode="r", buffering=None, encoding=None, newline=None,
+         closefd=True):
     r"""Replacement for the built-in open function.
 
     Args:
@@ -81,9 +82,12 @@ def open(file, mode="r", buffering=None, encoding=None, newline=None):
           other legal values, any `'\n'` characters written are
           translated to the given string.
 
+      closefd: optional argument to keep the underlying file descriptor
+               open when the file is closed.  It must not be false when
+               a filename is given.
+
     (*) If a file descriptor is given, it is closed when the returned
-    I/O object is closed.  If you don't want this to happen, use
-    os.dup() to create a duplicate file descriptor.
+    I/O object is closed, unless closefd=False is give.
 
     Mode strings characters:
       'r': open for reading (default)
@@ -138,7 +142,8 @@ def open(file, mode="r", buffering=None, encoding=None, newline=None):
                  (reading and "r" or "") +
                  (writing and "w" or "") +
                  (appending and "a" or "") +
-                 (updating and "+" or ""))
+                 (updating and "+" or ""),
+                 closefd)
     if buffering is None:
         buffering = -1
     if buffering < 0 and raw.isatty():
diff --git a/Lib/quopri.py b/Lib/quopri.py
index 62c0503877..6b3d13eca4 100755
--- a/Lib/quopri.py
+++ b/Lib/quopri.py
@@ -227,12 +227,14 @@ def main():
                 sys.stderr.write("%s: can't open (%s)\n" % (file, msg))
                 sts = 1
                 continue
-        if deco:
-            decode(fp, sys.stdout.buffer)
-        else:
-            encode(fp, sys.stdout.buffer, tabs)
-        if fp is not sys.stdin:
-            fp.close()
+        try:
+            if deco:
+                decode(fp, sys.stdout.buffer)
+            else:
+                encode(fp, sys.stdout.buffer, tabs)
+        finally:
+            if file != '-':
+                fp.close()
     if sts:
         sys.exit(sts)
 
diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index e826ff4b36..9d4163edc1 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -259,6 +259,9 @@ class IOTest(unittest.TestCase):
         self.assertEqual(f.write(a), n)
         f.close()
 
+    def test_closefd(self):
+        self.assertRaises(ValueError, io.open, test_support.TESTFN, 'w',
+                          closefd=False)
 
 class MemorySeekTestMixin:
 
diff --git a/Misc/NEWS b/Misc/NEWS
index 4ec628f7bc..41b8ab12b9 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -28,6 +28,9 @@ Core and Builtins
   with `Py_FileSystemDefaultEncoding` and a new API method 
   `PyUnicode_DecodeFSDefault(char*)` was added.
 
+- io.open() and _fileio.FileIO have grown a new argument closefd. A false
+  value disables the closing of the file descriptor.
+
 Extension Modules
 -----------------
 
diff --git a/Modules/_fileio.c b/Modules/_fileio.c
index bc707e8596..8469bb248f 100644
--- a/Modules/_fileio.c
+++ b/Modules/_fileio.c
@@ -33,6 +33,7 @@ typedef struct {
 	unsigned readable : 1;
 	unsigned writable : 1;
 	int seekable : 2; /* -1 means unknown */
+	int closefd : 1;
 	PyObject *weakreflist;
 } PyFileIOObject;
 
@@ -59,6 +60,13 @@ internal_close(PyFileIOObject *self)
 static PyObject *
 fileio_close(PyFileIOObject *self)
 {
+	if (!self->closefd) {
+		if (PyErr_WarnEx(PyExc_RuntimeWarning,
+				 "Trying to close unclosable fd!", 3) < 0) {
+			return NULL;
+		}
+		Py_RETURN_NONE;
+	}
 	errno = internal_close(self);
 	if (errno < 0) {
 		PyErr_SetFromErrno(PyExc_IOError);
@@ -119,7 +127,7 @@ static int
 fileio_init(PyObject *oself, PyObject *args, PyObject *kwds)
 {
 	PyFileIOObject *self = (PyFileIOObject *) oself;
-	static char *kwlist[] = {"file", "mode", NULL};
+	static char *kwlist[] = {"file", "mode", "closefd", NULL};
 	char *name = NULL;
 	char *mode = "r";
 	char *s;
@@ -130,6 +138,7 @@ fileio_init(PyObject *oself, PyObject *args, PyObject *kwds)
 	int rwa = 0, plus = 0, append = 0;
 	int flags = 0;
 	int fd = -1;
+	int closefd = 1;
 
 	assert(PyFileIO_Check(oself));
 	if (self->fd >= 0) {
@@ -138,8 +147,8 @@ fileio_init(PyObject *oself, PyObject *args, PyObject *kwds)
 			return -1;
 	}
 
-	if (PyArg_ParseTupleAndKeywords(args, kwds, "i|s:fileio",
-					kwlist, &fd, &mode)) {
+	if (PyArg_ParseTupleAndKeywords(args, kwds, "i|si:fileio",
+					kwlist, &fd, &mode, &closefd)) {
 		if (fd < 0) {
 			PyErr_SetString(PyExc_ValueError,
 					"Negative filedescriptor");
@@ -153,8 +162,9 @@ fileio_init(PyObject *oself, PyObject *args, PyObject *kwds)
 	    if (GetVersion() < 0x80000000) {
 		/* On NT, so wide API available */
 		PyObject *po;
-		if (PyArg_ParseTupleAndKeywords(args, kwds, "U|s:fileio",
-						kwlist, &po, &mode)) {
+		if (PyArg_ParseTupleAndKeywords(args, kwds, "U|si:fileio",
+						kwlist, &po, &mode, &closefd)
+						) {
 			widename = PyUnicode_AS_UNICODE(po);
 		} else {
 			/* Drop the argument parsing error as narrow
@@ -162,13 +172,13 @@ fileio_init(PyObject *oself, PyObject *args, PyObject *kwds)
 			PyErr_Clear();
 		}
 	    }
-	    if (widename == NULL) 
+	    if (widename == NULL)
 #endif
 	    {
-		if (!PyArg_ParseTupleAndKeywords(args, kwds, "et|s:fileio",
+		if (!PyArg_ParseTupleAndKeywords(args, kwds, "et|si:fileio",
 						 kwlist,
 						 Py_FileSystemDefaultEncoding,
-						 &name, &mode))
+						 &name, &mode, &closefd))
 			goto error;
 	    }
 	}
@@ -237,8 +247,16 @@ fileio_init(PyObject *oself, PyObject *args, PyObject *kwds)
 
 	if (fd >= 0) {
 		self->fd = fd;
+		self->closefd = closefd;
 	}
 	else {
+		self->closefd = 1;
+		if (!closefd) {
+			PyErr_SetString(PyExc_ValueError,
+                            "Cannot use closefd=True with file name");
+			goto error;
+		}
+
 		Py_BEGIN_ALLOW_THREADS
 		errno = 0;
 #ifdef MS_WINDOWS
@@ -270,7 +288,7 @@ fileio_dealloc(PyFileIOObject *self)
 	if (self->weakreflist != NULL)
 		PyObject_ClearWeakRefs((PyObject *) self);
 
-	if (self->fd >= 0) {
+	if (self->fd >= 0 && self->closefd) {
 		errno = internal_close(self);
 		if (errno < 0) {
 #ifdef HAVE_STRERROR
diff --git a/Objects/fileobject.c b/Objects/fileobject.c
index 9f63814ba1..4e18480b31 100644
--- a/Objects/fileobject.c
+++ b/Objects/fileobject.c
@@ -27,15 +27,15 @@ extern "C" {
 
 PyObject *
 PyFile_FromFd(int fd, char *name, char *mode, int buffering, char *encoding,
-	      char *newline)
+	      char *newline, int closefd)
 {
 	PyObject *io, *stream, *nameobj = NULL;
 
 	io = PyImport_ImportModule("io");
 	if (io == NULL)
 		return NULL;
-	stream = PyObject_CallMethod(io, "open", "isiss", fd, mode,
-				     buffering, encoding, newline);
+	stream = PyObject_CallMethod(io, "open", "isissi", fd, mode,
+				     buffering, encoding, newline, closefd);
 	Py_DECREF(io);
 	if (stream == NULL)
 		return NULL;
diff --git a/Python/import.c b/Python/import.c
index 24935547e6..be456f1b50 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -2588,7 +2588,7 @@ call_find_module(char *name, PyObject *path)
 				   (char*)PyUnicode_GetDefaultEncoding();
 		}
 		fob = PyFile_FromFd(fd, pathname, fdp->mode, -1,
-					(char*)encoding, NULL);
+				    (char*)encoding, NULL, 1);
 		if (fob == NULL) {
 			close(fd);
 			PyMem_FREE(found_encoding);
diff --git a/Python/pythonrun.c b/Python/pythonrun.c
index 330667a219..76da8fb7f7 100644
--- a/Python/pythonrun.c
+++ b/Python/pythonrun.c
@@ -720,7 +720,7 @@ initstdio(void)
 
 	/* Set sys.stdin */
 	if (!(std = PyFile_FromFd(fileno(stdin), "<stdin>", "r", -1,
-				      NULL, "\n"))) {
+				  NULL, "\n", 0))) {
 		goto error;
 	}
 	PySys_SetObject("__stdin__", std);
@@ -729,16 +729,16 @@ initstdio(void)
 
 	/* Set sys.stdout */
 	if (!(std = PyFile_FromFd(fileno(stdout), "<stdout>", "w", -1,
-				      NULL, "\n"))) {
+				  NULL, "\n", 0))) {
             goto error;
         }
 	PySys_SetObject("__stdout__", std);
 	PySys_SetObject("stdout", std);
 	Py_DECREF(std);
 
-	/* Set sys.stderr */
+	/* Set sys.stderr, replaces the preliminary stderr */
 	if (!(std = PyFile_FromFd(fileno(stderr), "<stderr>", "w", -1,
-				      NULL, "\n"))) {
+				  NULL, "\n", 0))) {
             goto error;
         }
         PySys_SetObject("__stderr__", std);