[Python-Dev] Fix import errors to have data

[Guido van Rossum]

I quickly whipped up this (procastinating on my OSCON keynote slides :-):

Index: import.c
===================================================================
RCS file: /cvsroot/python/python/dist/src/Python/import.c,v
retrieving revision 2.233
diff -c -u -r2.233 import.c
--- import.c	27 Jun 2004 16:51:46 -0000	2.233
+++ import.c	28 Jul 2004 18:57:15 -0000
@@ -572,17 +572,23 @@
 {
 	PyObject *modules = PyImport_GetModuleDict();
 	PyObject *m, *d, *v;
+	int pre_existing = 0;
 
-	m = PyImport_AddModule(name);
-	if (m == NULL)
-		return NULL;
+	if ((m = PyDict_GetItemString(modules, name)) != NULL &&
+	    PyModule_Check(m))
+		pre_existing = 1;
+	else {
+		m = PyImport_AddModule(name);
+		if (m == NULL)
+			return NULL;
+	}
 	/* If the module is being reloaded, we get the old module back
 	   and re-use its dict to exec the new code. */
 	d = PyModule_GetDict(m);
 	if (PyDict_GetItemString(d, "__builtins__") == NULL) {
 		if (PyDict_SetItemString(d, "__builtins__",
 					 PyEval_GetBuiltins()) != 0)
-			return NULL;
+			goto error;
 	}
 	/* Remember the filename as the __file__ attribute */
 	v = NULL;
@@ -601,7 +607,7 @@
 
 	v = PyEval_EvalCode((PyCodeObject *)co, d, d);
 	if (v == NULL)
-		return NULL;
+		goto error;
 	Py_DECREF(v);
 
 	if ((m = PyDict_GetItemString(modules, name)) == NULL) {
@@ -614,6 +620,11 @@
 	Py_INCREF(m);
 
 	return m;
+
+  error:
+	if (!pre_existing)
+		PyDict_DelItemString(modules, name); /* If it fails, too bad */
+	return NULL;
 }
 
 
Superficial testing suggests it works fine, except for one problem in
test_pkgimport which is testing specifically for the broken behavior.

BTW, building CVS Python gives these warnings for me:

/home/guido/projects/python/dist/src/Modules/cjkcodecs/_codecs_iso2022.c:120: array size missing in `designations'
/home/guido/projects/python/dist/src/Modules/cjkcodecs/_codecs_iso2022.c: In function `iso2022processesc':
/home/guido/projects/python/dist/src/Modules/cjkcodecs/_codecs_iso2022.c:306: warning: `esclen' might be used uninitialized in this function
/home/guido/projects/python/dist/src/Modules/cjkcodecs/_codecs_iso2022.c: At top level:
/home/guido/projects/python/dist/src/Modules/cjkcodecs/_codecs_iso2022.c:1053: warning: excess elements in array initializer
/home/guido/projects/python/dist/src/Modules/cjkcodecs/_codecs_iso2022.c:1053: warning: (near initialization for `iso2022_kr_config.designations')
/home/guido/projects/python/dist/src/Modules/cjkcodecs/_codecs_iso2022.c:1058: warning: excess elements in array initializer
[and many more similar]

Red Hat 7.3 using gcc 2.96.

--Guido van Rossum (home page: http://www.python.org/~guido/)