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, 2 insertions, 0 deletions

diff --git a/perl.c b/perl.c
index 157cd6b603..ed99612b7b 100644
--- a/perl.c
+++ b/perl.c
@@ -1003,6 +1003,7 @@ perl_destruct(pTHXx)
     SvREFCNT_dec(PL_utf8_tofold);
     SvREFCNT_dec(PL_utf8_idstart);
     SvREFCNT_dec(PL_utf8_idcont);
+    SvREFCNT_dec(PL_utf8_foldclosures);
     PL_utf8_alnum	= NULL;
     PL_utf8_ascii	= NULL;
     PL_utf8_alpha	= NULL;
@@ -1022,6 +1023,7 @@ perl_destruct(pTHXx)
     PL_utf8_tofold	= NULL;
     PL_utf8_idstart	= NULL;
     PL_utf8_idcont	= NULL;
+    PL_utf8_foldclosures = NULL;
 
     if (!specialWARN(PL_compiling.cop_warnings))
 	PerlMemShared_free(PL_compiling.cop_warnings);