regexec.c: Don't give up on fold matching early

As noted in the comments of the code, "a" =~ /[A]/i doesn't work currently
(except that regcomp.c knows about the ASCII characters and corrects for
it, but not always, for example in cases like "a" =~ /\p{Upper}/i.  This
patch catches all those).

It works by computing a list of all characters that (singly) fold to
another one, and then checking each of those.  The maximum length of
the list is 3 in the current Unicode standard.

I believe that a better long-term solution is to do this at compile
rather than execution time, by generating a closure of everything
matched.  But this can't be done now because the data structure would
need to be extensively revamped to list all non-byte characters, and
user-defined \p{} matches are not known at compile-time.

And it doesn't handle the multi-char folds.  There is a separate ticket
for those.

1 files changed, 1 insertions, 0 deletions

diff --git a/sv.c b/sv.c
index f3010af387..e2d498d8d8 100644
--- a/sv.c
+++ b/sv.c
@@ -13157,6 +13157,7 @@ perl_clone_using(PerlInterpreter *proto_perl, UV flags,
 
     PL_registered_mros  = hv_dup_inc(proto_perl->Iregistered_mros, param);
     PL_blockhooks	= av_dup_inc(proto_perl->Iblockhooks, param);
+    PL_utf8_foldclosures = hv_dup_inc(proto_perl->Iutf8_foldclosures, param);
 
     /* Call the ->CLONE method, if it exists, for each of the stashes
        identified by sv_dup() above.