avoid Unicode warnings in Carp

Only affects operation on old Perl versions.  Some special-case hackery
required for compatibility with old warnings.pm that eagerly loads Carp.

4 files changed, 52 insertions, 2 deletions

diff --git a/dist/Carp/lib/Carp.pm b/dist/Carp/lib/Carp.pm
index 5ca5e521bc..6ed248f12a 100644
--- a/dist/Carp/lib/Carp.pm
+++ b/dist/Carp/lib/Carp.pm
@@ -3,6 +3,27 @@ package Carp;
 { use 5.006; }
 use strict;
 use warnings;
+BEGIN {
+    # Very old versions of warnings.pm load Carp.  This can go wrong due
+    # to the circular dependency.  If warnings is invoked before Carp,
+    # then warnings starts by loading Carp, then Carp (above) tries to
+    # invoke warnings, and gets nothing because warnings is in the process
+    # of loading and hasn't defined its import method yet.  If we were
+    # only turning on warnings ("use warnings" above) this wouldn't be too
+    # bad, because Carp would just gets the state of the -w switch and so
+    # might not get some warnings that it wanted.  The real problem is
+    # that we then want to turn off Unicode warnings, but "no warnings
+    # 'utf8'" won't be effective if we're in this circular-dependency
+    # situation.  So, if warnings.pm is an affected version, we turn
+    # off all warnings ourselves by directly setting ${^WARNING_BITS}.
+    # On unaffected versions, we turn off just Unicode warnings, via
+    # the proper API.
+    if(!defined($warnings::VERSION) || eval($warnings::VERSION) < 1.06) {
+	${^WARNING_BITS} = "";
+    } else {
+	"warnings"->unimport("utf8");
+    }
+}
 
 BEGIN {
     no strict "refs";
@@ -24,7 +45,7 @@ BEGIN {
     }
 }
 
-our $VERSION = '1.31';
+our $VERSION = '1.32';
 
 our $MaxEvalLen = 0;
 our $Verbose    = 0;
diff --git a/dist/Carp/lib/Carp/Heavy.pm b/dist/Carp/lib/Carp/Heavy.pm
index a7a3327387..f0de26373a 100644
--- a/dist/Carp/lib/Carp/Heavy.pm
+++ b/dist/Carp/lib/Carp/Heavy.pm
@@ -2,7 +2,7 @@ package Carp::Heavy;
 
 use Carp ();
 
-our $VERSION = '1.31';
+our $VERSION = '1.32';
 
 1;
 
diff --git a/dist/Carp/t/baduni.t b/dist/Carp/t/baduni.t
new file mode 100644
index 0000000000..f2ec055866
--- /dev/null
+++ b/dist/Carp/t/baduni.t
@@ -0,0 +1,14 @@
+BEGIN { print "1..1\n"; }
+
+BEGIN { $^W = 1; }
+BEGIN { $SIG{__WARN__} = sub { die "WARNING: $_[0]" }; }
+
+use Carp ();
+
+my $badstr = do { no warnings "utf8"; "\x{ffff}" };
+sub dd { Carp::longmess() }
+dd($badstr);
+
+print "ok 1\n";
+
+1;
diff --git a/dist/Carp/t/baduni_warnings.t b/dist/Carp/t/baduni_warnings.t
new file mode 100644
index 0000000000..c5c876ce4b
--- /dev/null
+++ b/dist/Carp/t/baduni_warnings.t
@@ -0,0 +1,15 @@
+BEGIN { print "1..1\n"; }
+
+BEGIN { $^W = 1; }
+BEGIN { $SIG{__WARN__} = sub { die "WARNING: $_[0]" }; }
+
+use warnings;   # this may load Carp
+use Carp ();
+
+my $badstr = do { no warnings "utf8"; "\x{ffff}" };
+sub dd { Carp::longmess() }
+dd($badstr);
+
+print "ok 1\n";
+
+1;