uc suffers from The Unicode Bug when the unicode_strings feature isn't in enabled.

It works correctly (giving SS for ß) when the string the unicode_strings feature is enabled.

It works correctly (giving SS for ß) when the string is stored in the UTF8=1 format.

It works incorrectly (ß unchanged) otherwise. 

use open ":std", ":locale";
use feature qw( say );

my $ss = "\xDF";
utf8::upgrade(   my $ss_u = $ss );
utf8::downgrade( my $ss_d = $ss );

{
   no feature qw( unicode_strings );
   say uc( $ss_d );                    # ß
   say uc( $ss_u );                    # SS
}

{
   use feature qw( unicode_strings );
   say uc( $ss_d );                    # SS
   say uc( $ss_u );                    # SS
}

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In reply to Re^4: Memory Leak with XS but not pure C by ikegami
in thread Memory Leak with XS but not pure C by FrankFooty

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