utf8.c: Fix potential bug

Commit 87367d5f9dc9bbf7db1a6cf87820cea76571bf1a changed
core_invlist_init() to return not the swash, but the swash's inversion
list if small enough, allowing a faster binary search than a slower hash
look-up on small lists.  Calls to two functions that access swashes were
changed to make this transparent.  However, there are two more such
functions which were overlooked, and need to be upgraded to provide such
transparency, should they ever be called on swashes that have been
converted.  This commit fixes one of them, but leaves the other, with a
comment, as it's much harder to do, and will not ever likely be
called on such a swash (it is for internal core use only).

1 files changed, 28 insertions, 13 deletions

diff --git a/utf8.c b/utf8.c
index 829db7dcfc..05f03d5712 100644
--- a/utf8.c
+++ b/utf8.c
@@ -2788,8 +2788,8 @@ Perl__core_swash_init(pTHX_ const char* pkg, const char* name, SV *listsv, I32 m
      * by calling utf8_heavy.pl in the general case.  The returned value may be
      * the swash's inversion list instead if the input parameters allow it.
      * Which is returned should be immaterial to callers, as the only
-     * operations permitted on a swash, swash_fetch() and
-     * _get_swash_invlist(), handle both these transparently.
+     * operations permitted on a swash, swash_fetch(), _get_swash_invlist(),
+     * and swash_to_invlist() handle both these transparently.
      *
      * This interface should only be used by functions that won't destroy or
      * adversely change the swash, as doing so affects all other uses of the
@@ -3661,7 +3661,8 @@ Perl__swash_inversion_hash(pTHX_ SV* const swash)
     STRLEN lcur;
     HV *const hv = MUTABLE_HV(SvRV(swash));
 
-    /* The string containing the main body of the table */
+    /* The string containing the main body of the table.  This will have its
+     * assertion fail if the swash has been converted to its inversion list */
     SV** const listsvp = hv_fetchs(hv, "LIST", FALSE);
 
     SV** const typesvp = hv_fetchs(hv, "TYPE", FALSE);
@@ -3900,22 +3901,36 @@ Perl__swash_to_invlist(pTHX_ SV* const swash)
     HV *const hv = MUTABLE_HV(SvRV(swash));
     UV elements = 0;    /* Number of elements in the inversion list */
     U8 empty[] = "";
+    SV** listsvp;
+    SV** typesvp;
+    SV** bitssvp;
+    SV** extssvp;
+    SV** invert_it_svp;
 
-    /* The string containing the main body of the table */
-    SV** const listsvp = hv_fetchs(hv, "LIST", FALSE);
-    SV** const typesvp = hv_fetchs(hv, "TYPE", FALSE);
-    SV** const bitssvp = hv_fetchs(hv, "BITS", FALSE);
-    SV** const extssvp = hv_fetchs(hv, "EXTRAS", FALSE);
-    SV** const invert_it_svp = hv_fetchs(hv, "INVERT_IT", FALSE);
-
-    const U8* const typestr = (U8*)SvPV_nolen(*typesvp);
-    const STRLEN bits  = SvUV(*bitssvp);
-    const STRLEN octets = bits >> 3; /* if bits == 1, then octets == 0 */
+    U8* typestr;
+    STRLEN bits;
+    STRLEN octets; /* if bits == 1, then octets == 0 */
     U8 *x, *xend;
     STRLEN xcur;
 
     SV* invlist;
 
+    /* If not a hash, it must be the swash's inversion list instead */
+    if (SvTYPE(hv) != SVt_PVHV) {
+        return (SV*) hv;
+    }
+
+    /* The string containing the main body of the table */
+    listsvp = hv_fetchs(hv, "LIST", FALSE);
+    typesvp = hv_fetchs(hv, "TYPE", FALSE);
+    bitssvp = hv_fetchs(hv, "BITS", FALSE);
+    extssvp = hv_fetchs(hv, "EXTRAS", FALSE);
+    invert_it_svp = hv_fetchs(hv, "INVERT_IT", FALSE);
+
+    typestr = (U8*)SvPV_nolen(*typesvp);
+    bits  = SvUV(*bitssvp);
+    octets = bits >> 3; /* if bits == 1, then octets == 0 */
+
     PERL_ARGS_ASSERT__SWASH_TO_INVLIST;
 
     /* read $swash->{LIST} */