Simplify PyInit_timezone. (GH-9467)

Reduce the knotty preprocessor conditional logic, dedent unnecessarily nested
code, and handle errors properly.

The first edition of this change (afde1c1a)
failed (bpo-34715) because FreeBSD doesn't define the timezone globals. That's
why we're now checking for HAVE_DECL_TZNAME.

Modules/timemodule.c

@@ -1522,7 +1522,7 @@ PyDoc_STRVAR(get_clock_info_doc,
 \n\
 Get information of the specified clock.");
 
-#if !defined(HAVE_TZNAME) || defined(__GLIBC__) || defined(__CYGWIN__)
+#ifndef HAVE_DECL_TZNAME
 static void
 get_zone(char *zone, int n, struct tm *p)
 {
@@ -1543,7 +1543,7 @@ get_gmtoff(time_t t, struct tm *p)
     return timegm(p) - t;
 #endif
 }
-#endif /* !defined(HAVE_TZNAME) || defined(__GLIBC__) || defined(__CYGWIN__) */
+#endif // !HAVE_DECL_TZNAME
 
 static void
 PyInit_timezone(PyObject *m) {
@@ -1563,7 +1563,7 @@ PyInit_timezone(PyObject *m) {
 
     And I'm lazy and hate C so nyer.
      */
-#if defined(HAVE_TZNAME) && !defined(__GLIBC__) && !defined(__CYGWIN__)
+#ifdef HAVE_DECL_TZNAME
     PyObject *otz0, *otz1;
     tzset();
     PyModule_AddIntConstant(m, "timezone", timezone);
@@ -1574,11 +1574,20 @@ PyInit_timezone(PyObject *m) {
 #endif
     PyModule_AddIntConstant(m, "daylight", daylight);
     otz0 = PyUnicode_DecodeLocale(tzname[0], "surrogateescape");
+    if (otz0 == NULL) {
+        return;
+    }
     otz1 = PyUnicode_DecodeLocale(tzname[1], "surrogateescape");
-    PyModule_AddObject(m, "tzname", Py_BuildValue("(NN)", otz0, otz1));
-#else /* !HAVE_TZNAME || __GLIBC__ || __CYGWIN__*/
-    {
-#define YEAR ((time_t)((365 * 24 + 6) * 3600))
+    if (otz1 == NULL) {
+        Py_DECREF(otz0);
+        return;
+    }
+    PyObject *tzname_obj = Py_BuildValue("(NN)", otz0, otz1);
+    if (tzname_obj == NULL)
+        return;
+    PyModule_AddObject(m, "tzname", tzname_obj);
+#else // !HAVE_DECL_TZNAME
+    static const time_t YEAR = (365 * 24 + 6) * 3600;
     time_t t;
     struct tm p;
     long janzone, julyzone;
@@ -1594,34 +1603,23 @@ PyInit_timezone(PyObject *m) {
     julyzone = -get_gmtoff(t, &p);
     julyname[9] = '\0';
 
-        if( janzone < julyzone ) {
+    PyObject *tzname_obj;
+    if (janzone < julyzone) {
         /* DST is reversed in the southern hemisphere */
         PyModule_AddIntConstant(m, "timezone", julyzone);
         PyModule_AddIntConstant(m, "altzone", janzone);
-            PyModule_AddIntConstant(m, "daylight",
-                                    janzone != julyzone);
-            PyModule_AddObject(m, "tzname",
-                               Py_BuildValue("(zz)",
-                                             julyname, janname));
+        PyModule_AddIntConstant(m, "daylight", janzone != julyzone);
+        tzname_obj = Py_BuildValue("(zz)", julyname, janname);
     } else {
         PyModule_AddIntConstant(m, "timezone", janzone);
         PyModule_AddIntConstant(m, "altzone", julyzone);
-            PyModule_AddIntConstant(m, "daylight",
-                                    janzone != julyzone);
-            PyModule_AddObject(m, "tzname",
-                               Py_BuildValue("(zz)",
-                                             janname, julyname));
+        PyModule_AddIntConstant(m, "daylight", janzone != julyzone);
+        tzname_obj = Py_BuildValue("(zz)", janname, julyname);
     }
-    }
-#ifdef __CYGWIN__
-    tzset();
-    PyModule_AddIntConstant(m, "timezone", _timezone);
-    PyModule_AddIntConstant(m, "altzone", _timezone-3600);
-    PyModule_AddIntConstant(m, "daylight", _daylight);
-    PyModule_AddObject(m, "tzname",
-                       Py_BuildValue("(zz)", _tzname[0], _tzname[1]));
-#endif /* __CYGWIN__ */
-#endif /* !HAVE_TZNAME || __GLIBC__ || __CYGWIN__*/
+    if (tzname_obj == NULL)
+        return;
+    PyModule_AddObject(m, "tzname", tzname_obj);
+#endif // !HAVE_DECL_TZNAME
 }
 
 

PC/pyconfig.h

@@ -396,6 +396,10 @@ Py_NO_ENABLE_SHARED to find out.  Also support MS_NO_COREDLL for b/w compat */
 /* Define to 1 if you have the <direct.h> header file. */
 #define HAVE_DIRECT_H 1
 
+/* Define to 1 if you have the declaration of `tzname', and to 0 if you don't.
+   */
+#define HAVE_DECL_TZNAME 1
+
 /* Define if you have dirent.h.  */
 /* #define DIRENT 1 */