Address GH Perl#20571

The blamed commit, 04de022, exposed a bug in the module itself.  I will
submit a PR to fix it.

But this ticket did tell me that there was a problem with that commit.
It returned a C language value, CHAR_MAX, which doesn't really have a
corresponding concept in Perl.  Instead we use -1 to indicate that a
positive-valued variable is in some abnormal state.  This commit changes
to do that, and documents the changes, which should have been done in
04de022.

ext/POSIX/lib/POSIX.pm

@@ -4,7 +4,7 @@ use warnings;
 
 our ($AUTOLOAD, %SIGRT);
 
-our $VERSION = '2.09';
+our $VERSION = '2.10';
 
 require XSLoader;
 

ext/POSIX/lib/POSIX.pod

@@ -1015,6 +1015,18 @@ Here is how to query the database for the B<de> (Deutsch or German) locale.
 The members whose names begin with C<int_p_> and C<int_n_> were added by
 POSIX.1-2008 and are only available on systems that support them.
 
+A value of -1 returned for numeric entries indicates that the field is
+not applicable to the locale.  This is rare except in the C and related
+locales, which don't have most monetary values defined.  It can also
+happen, quirkily, in fields that are otherwise boolean to indicate that
+the value is kind of neither true nor false.  This happens in C<p_cs_precedes>
+and C<int_p_cs_precedes> when the currency symbol neither precedes nor
+succeeds a positive value but is infixed, by replacing the radix
+character.
+
+Prior to Perl v5.37.7, empty string fields and numeric fields with value
+-1 were omittted from the returned hash.
+
 =item C<localtime>
 
 This is identical to Perl's builtin C<localtime()> function for

locale.c

@@ -3520,15 +3520,21 @@ S_my_localeconv(pTHX_ const int item)
 
     /* Here, the hash has been completely populated.
      *
-     * Now go through all the string items and see if they should be marked as
-     * UTF-8 or not.  This would have been more convenient and faster to do
-     * while populating the hash in the first place, but that operation has to
-     * be done within a critical section, keeping other threads from executing,
-     * so only the minimal amount of work necessary is done at that time.
+     * Now go through all the items and:
+     *  a) For string items, see if they should be marked as UTF-8 or not.
+     *     This would have been more convenient and faster to do while
+     *     populating the hash in the first place, but that operation has to be
+     *     done within a critical section, keeping other threads from
+     *     executing, so only the minimal amount of work necessary is done at
+     *     that time.
+     *  b) For integer items, convert the C CHAR_MAX value into -1.  Again,
+     *     this could have been done in the critical section, but was deferred
+     *     to here to keep to the bare minimum amount the time spent owning the
+     *     processor. CHAR_MAX is a C concept for an 8-bit character type.
+     *     Perl has no such type; the closest fit is a -1.
      *
-     * XXX On unthreaded perls, and on platforms where localeconv (or
-     * localeconv_l if present) this code could be #ifdef'd out, and the
-     * UTF8ness determined at hash population time, at an extra maintenance
+     * XXX On unthreaded perls, this code could be #ifdef'd out, and the
+     * corrections determined at hash population time, at an extra maintenance
      * cost which khw doesn't think is worth it
      */
     for (unsigned int i = 0; i < 2; i++) {  /* Try both types of strings */
@@ -3589,6 +3595,28 @@ S_my_localeconv(pTHX_ const int item)
         }
     }   /* End of fixing up UTF8ness */
 
+
+    /* Examine each integer */
+    if (integers) while (1) {
+        const char * name = integers->name;
+
+        if (! name) {   /* Reached the end */
+            break;
+        }
+
+        SV ** value = hv_fetch(hv, name, strlen(name), true);
+        if (! value) {
+            continue;
+        }
+
+        /* Change CHAR_MAX to -1 */
+        if (SvIV(*value) == CHAR_MAX) {
+            sv_setiv(*value, -1);
+        }
+
+        integers++;   /* Iterate */
+    }
+
     return hv;
 }
 
@@ -4336,14 +4364,14 @@ S_my_langinfo_i(pTHX_
 
             /* The modification is to prefix the localeconv() return with a
              * single byte, calculated as follows: */
-            char prefix = (LIKELY(SvIV(precedes) != CHAR_MAX))
+            char prefix = (LIKELY(SvIV(precedes) != -1))
                           ? ((precedes != 0) ?  '-' : '+')
 
                             /* khw couldn't find any documentation that
-                             * CHAR_MAX is the signal, but cygwin uses it
-                             * thusly, and it makes sense given that CHAR_MAX
-                             * indicates the value isn't used, so it neither
-                             * precedes nor succeeds */
+                             * CHAR_MAX (which we modify to -1) is the signal,
+                             * but cygwin uses it thusly, and it makes sense
+                             * given that CHAR_MAX indicates the value isn't
+                             * used, so it neither precedes nor succeeds */
                           : '.';
 
             /* Now get CRNCYSTR */

pod/perldelta.pod

@@ -198,6 +198,13 @@ L<parent> has been upgraded to version 2.39.
 
 L<podlators> has been upgraded to version 5.00.
 
+=item *
+
+L<POSIX> has been upgraded from version 2.09 to 2.10.  All fields known
+to the platform in L<localeconv(3)> are now returned by
+L<POSIX/localeconv>.  Previously, empty string fields and numeric fields
+that aren't applicable to the current locale were omitted.
+
 =back
 
 =head2 Removed Modules and Pragmata