Clean up the fix to #9324 with some of the suggestions raised on python-dev

in response to the original checkin.

Move the validation from the original loop into a switch statement,
and adjust a platform check in the tests.

Lib/test/test_signal.py

@@ -9,9 +9,8 @@ import subprocess
 import traceback
 import sys, os, time, errno
 
-if sys.platform == 'os2' or sys.platform == 'riscos':
-    raise unittest.SkipTest("Can't test signal on %s" % \
-                                   sys.platform)
+if sys.platform in ('os2', 'riscos'):
+    raise unittest.SkipTest("Can't test signal on %s" % sys.platform)
 
 
 class HandlerBCalled(Exception):

Modules/signalmodule.c

@@ -255,21 +255,20 @@ signal_signal(PyObject *self, PyObject *args)
     int sig_num;
     PyObject *old_handler;
     void (*func)(int);
-#ifdef MS_WINDOWS
-    int cur_sig, num_valid_sigs = 6;
-    static int valid_sigs[] = {SIGABRT, SIGFPE, SIGILL, SIGINT,
-                               SIGSEGV, SIGTERM};
-    BOOL valid_sig = FALSE;
-#endif
     if (!PyArg_ParseTuple(args, "iO:signal", &sig_num, &obj))
         return NULL;
 #ifdef MS_WINDOWS
     /* Validate that sig_num is one of the allowable signals */
-    for (cur_sig = 0; cur_sig < num_valid_sigs; cur_sig++)
-        valid_sig |= (sig_num == valid_sigs[cur_sig]);
-    if (!valid_sig) {
-        PyErr_SetString(PyExc_ValueError, "signal number out of range");
-        return NULL;
+    switch (sig_num) {
+        case SIGABRT: break;
+        case SIGFPE: break;
+        case SIGILL: break;
+        case SIGINT: break;
+        case SIGSEGV: break;
+        case SIGTERM: break;
+        default:
+            PyErr_SetString(PyExc_ValueError, "invalid signal value");
+            return NULL;
     }
 #endif
 #ifdef WITH_THREAD