Issue 3723: Fixed initialization of subinterpreters

The patch fixes several issues with Py_NewInterpreter as well as the demo for multiple subinterpreters.
Most of the patch was written by MvL with help from Benjamin, Amaury and me. Graham Dumpleton has verified that this patch fixes an issue with mod_wsgi.

Demo/embed/importexc.c

 #include <Python.h>
 
-char* cmd = "import exceptions";
+#if 0
+char* cmd = "import codecs, encodings.utf_8, types; print(types)";
+#else
+char* cmd = "import types; print(types)";
+#endif
 
 int main()
 {
+	printf("Initialize interpreter\n");
 	Py_Initialize();
 	PyEval_InitThreads();
 	PyRun_SimpleString(cmd);
 	Py_EndInterpreter(PyThreadState_Get());
 
+	printf("\nInitialize subinterpreter\n");
 	Py_NewInterpreter();
 	PyRun_SimpleString(cmd);
 	Py_Finalize();

Include/pystate.h

@@ -27,6 +27,7 @@ typedef struct _is {
     PyObject *codec_search_path;
     PyObject *codec_search_cache;
     PyObject *codec_error_registry;
+    int codecs_initialized;
 
 #ifdef HAVE_DLOPEN
     int dlopenflags;

Misc/NEWS

@@ -15,6 +15,8 @@ What's New in Python 3.0 beta 5
 Core and Builtins
 -----------------
 
+- Issue 3723: Fixed initialization of subinterpreters.
+
 - Issue #4213: The file system encoding is now normalized by the
   codec subsystem, for example UTF-8 is turned into utf-8.
 

Objects/unicodeobject.c

@@ -1346,6 +1346,19 @@ PyObject *PyUnicode_AsEncodedString(PyObject *unicode,
 #endif
 	else if (strcmp(encoding, "ascii") == 0)
 	    return PyUnicode_AsASCIIString(unicode);
+        /* During bootstrap, we may need to find the encodings
+           package, to load the file system encoding, and require the
+           file system encoding in order to load the encodings
+           package.
+
+           Break out of this dependency by assuming that the path to
+           the encodings module is ASCII-only.  XXX could try wcstombs
+           instead, if the file system encoding is the locale's
+           encoding. */
+        else if (Py_FileSystemDefaultEncoding &&
+                 strcmp(encoding, Py_FileSystemDefaultEncoding) == 0 &&
+                 !PyThreadState_GET()->interp->codecs_initialized)
+	    return PyUnicode_AsASCIIString(unicode);            
     }
 
     /* Encode via the codec registry */

Python/bltinmodule.c

@@ -2282,7 +2282,7 @@ static struct PyModuleDef builtinsmodule = {
 	PyModuleDef_HEAD_INIT,
 	"builtins",
 	builtin_doc,
-	0,
+	-1, /* multiple "initialization" just copies the module dict. */
 	builtin_methods,
 	NULL,
 	NULL,

Python/codecs.c

@@ -869,5 +869,6 @@ static int _PyCodecRegistry_Init(void)
 	return -1;
     }
     Py_DECREF(mod);
+    interp->codecs_initialized = 1;
     return 0;
 }

Python/pystate.c

@@ -76,6 +76,7 @@ PyInterpreterState_New(void)
 		interp->codec_search_path = NULL;
 		interp->codec_search_cache = NULL;
 		interp->codec_error_registry = NULL;
+		interp->codecs_initialized = 0;
 #ifdef HAVE_DLOPEN
 #ifdef RTLD_NOW
                 interp->dlopenflags = RTLD_NOW;

Python/pythonrun.c

@@ -562,8 +562,13 @@ Py_NewInterpreter(void)
 			goto handle_error;
 		Py_INCREF(interp->builtins);
 	}
+
+	/* initialize builtin exceptions */
+	_PyExc_Init();
+
 	sysmod = _PyImport_FindExtension("sys", "sys");
 	if (bimod != NULL && sysmod != NULL) {
+		PyObject *pstderr;
 		interp->sysdict = PyModule_GetDict(sysmod);
 		if (interp->sysdict == NULL)
 			goto handle_error;
@@ -571,7 +576,18 @@ Py_NewInterpreter(void)
 		PySys_SetPath(Py_GetPath());
 		PyDict_SetItemString(interp->sysdict, "modules",
 				     interp->modules);
+		/* Set up a preliminary stderr printer until we have enough
+		   infrastructure for the io module in place. */
+		pstderr = PyFile_NewStdPrinter(fileno(stderr));
+		if (pstderr == NULL)
+			Py_FatalError("Py_Initialize: can't set preliminary stderr");
+		PySys_SetObject("stderr", pstderr);
+		PySys_SetObject("__stderr__", pstderr);
+
 		_PyImportHooks_Init();
+                if (initstdio() < 0)
+                    Py_FatalError(
+                        "Py_Initialize: can't initialize sys standard streams");
 		initmain();
 		if (!Py_NoSiteFlag)
 			initsite();

Python/sysmodule.c

@@ -1231,7 +1231,7 @@ static struct PyModuleDef sysmodule = {
 	PyModuleDef_HEAD_INIT,
 	"sys",
 	sys_doc,
-	0,
+	-1, /* multiple "initialization" just copies the module dict. */
 	sys_methods,
 	NULL,
 	NULL,