Fix importing of shared libraries from inside packages.

This is a bit of a hack: when the shared library is loaded, the module
name is "package.module", but the module calls Py_InitModule*() with just
"module" for the name.  The shared library loader squirrels away the true
name of the module in _Py_PackageContext, and Py_InitModule*() will
substitute this (if the name actually matches).

Python/importdl.c

@@ -233,6 +233,7 @@ _PyImport_LoadDynamicModule(name, pathname, fp)
 #else
 	PyObject *m, *d, *s;
 	char funcname[258];
+	char *lastdot, *shortname, *packagecontext;
 	dl_funcptr p = NULL;
 #ifdef USE_SHLIB
 	static struct {
@@ -252,7 +253,16 @@ _PyImport_LoadDynamicModule(name, pathname, fp)
 		Py_INCREF(m);
 		return m;
 	}
-	sprintf(funcname, FUNCNAME_PATTERN, name);
+	lastdot = strrchr(name, '.');
+	if (lastdot == NULL) {
+		packagecontext = NULL;
+		shortname = name;
+	}
+	else {
+		packagecontext = name;
+		shortname = lastdot+1;
+	}
+	sprintf(funcname, FUNCNAME_PATTERN, shortname);
 #ifdef USE_SHLIB
 	if (fp != NULL) {
 		int i;
@@ -519,11 +529,14 @@ _PyImport_LoadDynamicModule(name, pathname, fp)
   got_it:
 #endif
 	if (p == NULL) {
-		PyErr_SetString(PyExc_ImportError,
-		   "dynamic module does not define init function");
+		PyErr_Format(PyExc_ImportError,
+		   "dynamic module does not define init function (%s)",
+			     funcname);
 		return NULL;
 	}
+	_Py_PackageContext = packagecontext;
 	(*p)();
+	_Py_PackageContext = NULL;
 	if (PyErr_Occurred())
 		return NULL;
 	if (_PyImport_FixupExtension(name, pathname) == NULL)

Python/modsupport.c

@@ -39,6 +39,9 @@ typedef extended va_double;
 typedef double va_double;
 #endif
 
+/* Package context -- the full module name for package imports */
+char *_Py_PackageContext = NULL;
+
 /* Py_InitModule4() parameters:
    - name is the module name
    - methods is the list of top-level functions
@@ -69,6 +72,13 @@ Py_InitModule4(name, methods, doc, passthrough, module_api_version)
 	if (module_api_version != PYTHON_API_VERSION)
 		fprintf(stderr, api_version_warning,
 			name, PYTHON_API_VERSION, name, module_api_version);
+	if (_Py_PackageContext != NULL) {
+		char *p = strrchr(_Py_PackageContext, '.');
+		if (p != NULL && strcmp(name, p+1) == 0) {
+			name = _Py_PackageContext;
+			_Py_PackageContext = NULL;
+		}
+	}
 	if ((m = PyImport_AddModule(name)) == NULL)
 		return NULL;
 	d = PyModule_GetDict(m);