locale.c: Refactor a static function

S_new_numeric() is called after the LC_NUMERIC category is changed, to
update various ancillary information Perl keeps.

This reorders the function so that on POSIX 2008 platforms, the numeric
object is created earlier.  This allows for fewer operations on those
platforms, as we already have the correct value in place for querying
what the radix and thousands separator characters are.

Explanatory comments are also added.

locale.c

@@ -1555,6 +1555,7 @@ S_set_numeric_radix(pTHX_ const bool use_locale)
 STATIC void
 S_new_numeric(pTHX_ const char *newnum)
 {
+    const char *save_newnum;
 
 #  ifndef USE_LOCALE_NUMERIC
 
@@ -1604,10 +1605,6 @@ S_new_numeric(pTHX_ const char *newnum)
      *                  such platforms.
      */
 
-    char *save_newnum;
-    const char * scratch_buffer = NULL;
-    Size_t buf_size = 0;
-
     if (! newnum) {
         Safefree(PL_numeric_name);
         PL_numeric_name = NULL;
@@ -1619,28 +1616,6 @@ S_new_numeric(pTHX_ const char *newnum)
 
     save_newnum = savepv(newnum);
     PL_numeric_underlying = TRUE;
-    PL_numeric_standard = isNAME_C_OR_POSIX(save_newnum);
-
-#    ifndef TS_W32_BROKEN_LOCALECONV
-
-    /* If its name isn't C nor POSIX, it could still be indistinguishable from
-     * them.  But on broken Windows systems calling my_langinfo() for
-     * THOUSEP can currently (but rarely) cause a race, so avoid doing that,
-     * and just always change the locale if not C nor POSIX on those systems */
-    if (! PL_numeric_standard) {
-        PL_numeric_standard =    strEQ(C_decimal_point,
-                                       my_langinfo_c(RADIXCHAR, LC_NUMERIC,
-                                                     NULL, &scratch_buffer,
-                                                     &buf_size, NULL))
-                               && strEQ(C_thousands_sep,
-                                       my_langinfo_c(THOUSEP, LC_NUMERIC,
-                                                     NULL,
-                                                     &scratch_buffer,
-                                                     &buf_size, NULL));
-        Safefree(scratch_buffer);
-    }
-
-#    endif
 
     /* Save the new name if it isn't the same as the previous one, if any */
     if (PL_numeric_name && strEQ(PL_numeric_name, save_newnum)) {
@@ -1652,8 +1627,6 @@ S_new_numeric(pTHX_ const char *newnum)
         PL_numeric_name = save_newnum;
     }
 
-    PL_numeric_underlying_is_standard = PL_numeric_standard;
-
 #  ifdef USE_POSIX_2008_LOCALE
 
     /* We keep a special object for easy switching to */
@@ -1663,6 +1636,55 @@ S_new_numeric(pTHX_ const char *newnum)
 
 #    endif
 
+    if (isNAME_C_OR_POSIX(PL_numeric_name)) {
+        PL_numeric_standard = TRUE;
+    }
+    else { /* If its name isn't C nor POSIX, it could still be
+              indistinguishable from them. */
+        const char * scratch_buffer = NULL;
+
+        PL_numeric_standard = strEQ(C_decimal_point,
+                                  my_langinfo_c(RADIXCHAR, LC_NUMERIC,
+                                                USE_UNDERLYING_NUMERIC,
+                                                &scratch_buffer, NULL,
+                                                NULL));
+        Safefree(scratch_buffer);
+
+#    ifndef TS_W32_BROKEN_LOCALECONV
+
+        scratch_buffer = NULL;
+
+    /* If the radix isn't the same as C's, we know it is distinguishable from
+     * C; otherwise check the thousands separator too.  Only if both are the
+     * same as C's is the locale indistinguishable from C.
+     *
+     * But on earlier Windows versions, there is a potential race.  This code
+     * knows that localeconv() (elsewhere in this file) will be used to extract
+     * the needed value, and localeconv() was buggy for quite a while, and that
+     * code in this file hence uses a workaround.  And that workaround may have
+     * an (unlikely) race.  Gathering the radix uses a different workaround on
+     * Windows that doesn't involve a race.  It might be possible to do the
+     * same for this (patches welcome).
+     *
+     * Until then khw doesn't think it's worth even the small risk of a race to
+     * get this value, which in almost all locales is empty, and doesn't appear
+     * to be used in any of the Micrsoft library routines anyway. */
+
+        if (PL_numeric_standard) {
+            PL_numeric_standard = strEQ(C_thousands_sep,
+                                        my_langinfo_c(THOUSEP, LC_NUMERIC,
+                                                      USE_UNDERLYING_NUMERIC,
+                                                      &scratch_buffer, NULL,
+                                                      NULL));
+        }
+        Safefree(scratch_buffer);
+
+#    endif
+
+    }
+
+    PL_numeric_underlying_is_standard = PL_numeric_standard;
+
     DEBUG_L( PerlIO_printf(Perl_debug_log,
                             "Called new_numeric with %s, PL_numeric_name=%s\n",
                             newnum, PL_numeric_name));