vutil.c: Simplify locale handling when using POSIX 2008

I read the code over and realized that there was a much simpler way to
do things when using POSIX 2008 locales.  Instead of all the rigamorole
about saving/restoring locales, just toggle to the C object using the
thread-safe uselocale() libc function.  This trivally gets us to the C
locale, and hence a dot radix.

Author: khwilliamson

vutil/vutil.c

@@ -668,79 +668,26 @@ Perl_upg_version(pTHX_ SV *ver, bool qv)
                 locale_name_on_entry = NULL;
             }
 
-# else
-            const locale_t locale_obj_on_entry = uselocale((locale_t) 0);
-            const char * locale_name_on_entry = NULL;
-            DECLARATION_FOR_LC_NUMERIC_MANIPULATION;
-
-            if (locale_obj_on_entry == LC_GLOBAL_LOCALE) {
-
-                /* in the global locale, we can call system setlocale and if it
-                 * isn't C, set it to C. */
-                LC_NUMERIC_LOCK(0);
-
-                locale_name_on_entry = setlocale(LC_NUMERIC, NULL);
-                if (   strNE(locale_name_on_entry, "C")
-                    && strNE(locale_name_on_entry, "POSIX"))
-                {
-                    /* the setlocale() call might free or overwrite the name */
-                    locale_name_on_entry = savepv(locale_name_on_entry);
-                    setlocale(LC_NUMERIC, "C");
-                }
-                else {  /* This value indicates to the restore code that we
-                           didn't change the locale */
-                    locale_name_on_entry = NULL;
-                }
-            }
-            else if (locale_obj_on_entry == PL_underlying_numeric_obj) {
-                /* Here, the locale appears to have been changed to use the
-                 * program's underlying locale.  Just use our mechanisms to
-                 * switch back to C.   It might be possible for this pointer to
-                 * actually refer to something else if it got released and
-                 * reused somehow.  But it doesn't matter, our mechanisms will
-                 * work even so */
-                STORE_LC_NUMERIC_SET_STANDARD();
-            }
-            else if (locale_obj_on_entry != PL_C_locale_obj) {
-                /* The C object should be unchanged during a program's
-                 * execution, so it should be safe to assume it means what it
-                 * says, so if we are in it, no locale change is required.
-                 * Otherwise, simply use the thread-safe operation. */
-                uselocale(PL_C_locale_obj);
-            }
-
-# endif
             /* Prevent recursed calls from trying to change back */
             LOCK_LC_NUMERIC_STANDARD();
-#endif
-            GET_NUMERIC_VERSION(ver, sv, tbuf, buf, len);
 
-#ifdef USE_LOCALE_NUMERIC
+            GET_NUMERIC_VERSION(ver, sv, tbuf, buf, len);
 
             UNLOCK_LC_NUMERIC_STANDARD();
 
-#  ifndef USE_POSIX_2008_LOCALE
-
             if (locale_name_on_entry) {
                 setlocale(LC_NUMERIC, locale_name_on_entry);
                 Safefree(locale_name_on_entry);
             }
 
             LC_NUMERIC_UNLOCK;  /* End critical section */
-#  else
-
-            if (locale_name_on_entry) {
-                setlocale(LC_NUMERIC, locale_name_on_entry);
-                Safefree(locale_name_on_entry);
-                LC_NUMERIC_UNLOCK;
-            }
-            else if (locale_obj_on_entry == PL_underlying_numeric_obj) {
-                RESTORE_LC_NUMERIC();
-            }
-            else if (locale_obj_on_entry != PL_C_locale_obj) {
-                uselocale(locale_obj_on_entry);
-            }
 
+#  else
+            /* With POSIX 2008, all we have to do is toggle to the C locale
+             * just long enough to get the value (which should have a dot). */
+            const locale_t locale_obj_on_entry = uselocale(PL_C_locale_obj);
+            GET_NUMERIC_VERSION(ver, sv, tbuf, buf, len);
+            uselocale(locale_obj_on_entry);
 #  endif
 
         }