--- CBOR-XS/XS.xs	2020/12/04 02:57:14	1.70
+++ CBOR-XS/XS.xs	2021/10/23 03:00:31	1.73
@@ -30,6 +30,9 @@
 # define SvREFCNT_dec_NN(sv) SvREFCNT_dec (sv)
 #endif
 
+// perl's is_utf8_string interprets len=0 as "calculate len", but we want it to mean 0
+#define cbor_is_utf8_string(str,len) (!(len) || is_utf8_string ((str), (len)))
+
 // known major and minor types
 enum cbor_type
 {
@@ -203,7 +206,7 @@
 }
 
 // minimum length of a string to be registered for stringref
-ecb_inline int
+ecb_inline STRLEN
 minimum_string_length (UV idx)
 {
   return idx <=          23 ?  3
@@ -989,7 +992,7 @@
         dec->cur += len;
 
         if (ecb_expect_false (dec->cbor.flags & F_VALIDATE_UTF8))
-          if (!is_utf8_string (key, len))
+          if (!cbor_is_utf8_string ((U8 *)key, len))
             ERR ("corrupted CBOR data (invalid UTF-8 in map key)");
 
         hv_store (hv, key, -len, decode_sv (dec), 0);
@@ -1128,7 +1131,7 @@
   if (utf8)
     {
       if (ecb_expect_false (dec->cbor.flags & F_VALIDATE_UTF8))
-        if (!is_utf8_string (SvPVX (sv), SvCUR (sv)))
+        if (!cbor_is_utf8_string (SvPVX (sv), SvCUR (sv)))
           ERR ("corrupted CBOR data (invalid UTF-8 in text string)");
 
       SvUTF8_on (sv);
@@ -1571,6 +1574,7 @@
 
                       case MAJOR_MAP     >> MAJOR_SHIFT:
                         len <<= 1;
+                        /* FALLTHROUGH */
                       case MAJOR_ARRAY   >> MAJOR_SHIFT:
                         if (len)
                           {