lib/locale.pm: Add an assertion

It turns out that the code assumes that the values for LC_CTYPE,
LC_MESSAGES, ...  are small non-negative numbers, as a bit position is
reserved for each of these.  It's better to make this assumption
explicit rather than getting hard-to-find failures.

(LC_ALL doesn't have to be of this form, and is in fact -1 on AIX)

1 files changed, 12 insertions, 2 deletions

diff --git a/lib/locale.pm b/lib/locale.pm
index 9cc243f86c..53c01ffd37 100644
--- a/lib/locale.pm
+++ b/lib/locale.pm
@@ -102,10 +102,20 @@ sub import {
             }
 
             # Map our names to the ones defined by POSIX
-            $arg = "LC_" . uc($arg);
+            my $LC = "LC_" . uc($arg);
 
-            my $bit = eval "&POSIX::$arg";
+            my $bit = eval "&POSIX::$LC";
             if (defined $bit) {
+
+                # Verify our assumption.
+                if (! ($bit >= 0 && $bit < 31)) {
+                    require Carp;
+                    Carp::croak("Cannot have ':$arg' parameter to 'use locale'"
+                              . " on this platform.  Use the 'perlbug' utility"
+                              . " to report this problem, or send email to"
+                              . " 'perlbug\@perl.org'.  $LC=$bit");
+                }
+
                 # 1 is added so that the pseudo-category :characters, which is
                 # -1, comes out 0.
                 $^H{locale} |= 1 << ($bit + 1);