loc_tools.pl: Fix locales_enabled()

This commit properly returns the new list it is supposed to, clarifies
the documentation.

Fixes GH #18245

1 files changed, 35 insertions, 21 deletions

diff --git a/t/loc_tools.pl b/t/loc_tools.pl
index 927f0254a5..f4b99775e1 100644
--- a/t/loc_tools.pl
+++ b/t/loc_tools.pl
@@ -187,26 +187,35 @@ sub valid_locale_categories() {
 }
 
 sub locales_enabled(;$) {
-    # Returns 0 if no locale handling is available on this platform; otherwise
-    # 1.
+    # If no parameter is specified, the function returns 1 if there is any
+    # "safe" locale handling available to the caller; otherwise 0.  Safeness
+    # is defined here as the caller operating in the main thread of a program,
+    # or if threaded locales are safe on the platform and Configured to be
+    # used.  This sub is used for testing purposes, and for those, this
+    # definition of safety is sufficient, and necessary to get some tests to
+    # run on certain configurations on certain platforms.  But beware that the
+    # main thread can change the locale of any subthreads unless
+    # ${^SAFE_LOCALES} is non-zero.
     #
-    # The optional parameter is a reference to a list of individual POSIX
-    # locale categories.  If any of the individual categories specified by the
-    # optional parameter is all digits (and an optional leading minus), it is
-    # taken to be the C enum for the category (e.g., &POSIX::LC_CTYPE).
-    # Otherwise it should be a string name of the category, like 'LC_TIME'.
-    # The initial 'LC_' is optional.  It is a fatal error to call this with
-    # something that isn't a known category to this file.
+    # Use the optional parameter to discover if a particular category or
+    # categories are available on the system.  1 is returned if the global
+    # criteria described in the previous paragraph are true, AND if all the
+    # specified categories are available on the platform and Configured to be
+    # used.  Otherwise 0 is returned.  The parameter is either a single POSIX
+    # locale category or a reference to a list of them.  Each category must be
+    # its name as a string, like 'LC_TIME' (the initial 'LC_' is optional), or
+    # the number this platform uses to signify the category (e.g.,
+    # 'locales_enabled(&POSIX::LC_CTYPE)'
     #
-    # This optional parameter denotes which POSIX locale categories must be
-    # available on the platform.  If any aren't available, this function
-    # returns 0; otherwise it returns 1 and changes the list for the caller so
-    # that any category names are converted into their equivalent numbers, and
-    # sorts it to match the expectations of _trylocale.
+    # When the function returns 1 and a parameter was specified as a list
+    # reference, the reference will be altered on return to point to an
+    # equivalent list such that  the categories are numeric instead of strings
+    # and sorted to meet the input expectations of _trylocale().
     #
-    # It is acceptable for the second parameter to be just a simple scalar
-    # denoting a single category (either name or number).  No conversion into
-    # a number is done in this case.
+    # It is a fatal error to call this with something that isn't a known
+    # category to this file.  If this happens, look first for a typo, and
+    # second if you are using a category unknown to Perl.  In the latter case
+    # a bug report should be submitted.
 
     # khw cargo-culted the '?' in the pattern on the next line.
     return 0 if $Config{ccflags} =~ /\bD?NO_LOCALE\b/;
@@ -235,7 +244,7 @@ sub locales_enabled(;$) {
     # Done with the global possibilities.  Now check if any passed in category
     # is disabled.
 
-    my $categories_ref = shift;
+    my $categories_ref = $_[0];
     my $return_categories_numbers = 0;
     my @categories_numbers;
     my $has_LC_ALL = 0;
@@ -244,10 +253,15 @@ sub locales_enabled(;$) {
     if (defined $categories_ref) {
         my @local_categories_copy;
 
-        if (ref $categories_ref) {
-            @local_categories_copy = @$$categories_ref;
+        my $reftype = ref $categories_ref;
+        if ($reftype eq 'ARRAY') {
+            @local_categories_copy = @$categories_ref;
             $return_categories_numbers = 1;
         }
+        elsif ($reftype ne "") {
+            die "Parameter to locales_enabled() must be an ARRAY;"
+              . " instead you used a $reftype";
+        }
         else {  # Single category passed in
             @local_categories_copy = $categories_ref;
         }
@@ -306,7 +320,7 @@ sub locales_enabled(;$) {
         if ($has_LC_ALL) {
             push @categories_numbers, $category_number{'ALL'};
         }
-        $$categories_ref = \@categories_numbers;
+        $_[0]->@* = @categories_numbers;
     }
 
     return 1;