check_utf8_print: Use utf8_to_uv_flags.

This replaces the old-style utf8n_to_uvchr()

Author: khwilliamson

utf8.c

@@ -1246,12 +1246,14 @@ C<utf8n_to_uvchr> is more like an extension of C<utf8_to_uvchr_buf>, but
 with fewer quirks, and a different method of specifying the bytes in C<s> it is
 allowed to examine.  It has a C<curlen> parameter instead of an C<e> parameter,
 so the furthest byte in C<s> it can look at is S<C<s + curlen - 1>>.  Its
-return value is, like C<utf8_to_uvchr_buf>, ambiguous with respect to the NUL
-and REPLACEMENT characters, but the value of C<*retlen> can be relied on
-(except with the C<UTF8_CHECK_ONLY> flag described below) to know where the
-next possible character along C<s> starts, removing that quirk.  Hence, you
-always should use C<*retlen> to determine where the next character in C<s>
-starts.
+failure return value is not dependent on if warnings are enabled or not.  It is
+always 0 upon failure.  But like C<utf8_to_uvchr_buf>, 0 could also be the
+return for a successful translation of an input C<NUL> character.  Use the same
+method given above for disambiguating this.  Unlike C<utf8_to_uvchr_buf>,
+C<*retlen> can be relied on (except with the C<UTF8_CHECK_ONLY> flag described
+below) to know where the next possible character along C<s> starts, removing
+that quirk.  Hence, you always should use C<*retlen> to determine where the
+next character in C<s> starts.
 
 These functions have an additional parameter, C<flags>, besides the ones in
 C<utf8_to_uv> and C<utf8_to_uvchr_buf>, which can be used to broaden or
@@ -2080,7 +2082,7 @@ Perl_utf8_to_uv_msgs_helper_(const U8 * const s0,
             switch (this_problem) {
               default:
                 Perl_croak(aTHX_ "panic: Unexpected case value in "
-                                 " utf8n_to_uvchr_msgs() %" U32uf,
+                                 " utf8_to_uv_msgs() %" U32uf,
                            this_problem);
                 /* NOTREACHED */
                 break;
@@ -4687,8 +4689,10 @@ Perl_check_utf8_print(pTHX_ const U8* s, const STRLEN len)
                 if (   ckWARN_d(WARN_NON_UNICODE)
                     || UNLIKELY(does_utf8_overflow(s, s + len) >= ALMOST_CERTAINLY_OVERFLOWS))
                 {
+                    UV dummy;
+
                     /* A side effect of this function will be to warn */
-                    (void) utf8n_to_uvchr(s, e - s, NULL, UTF8_WARN_SUPER);
+                    (void) utf8_to_uv_flags(s, e, &dummy, NULL, UTF8_WARN_SUPER);
                     ok = FALSE;
                 }
             }
@@ -4707,8 +4711,10 @@ Perl_check_utf8_print(pTHX_ const U8* s, const STRLEN len)
             else if (   UNLIKELY(UTF8_IS_NONCHAR(s, e))
                      && (ckWARN_d(WARN_NONCHAR)))
             {
+                UV dummy;
+
                 /* A side effect of this function will be to warn */
-                (void) utf8n_to_uvchr(s, e - s, NULL, UTF8_WARN_NONCHAR);
+                (void) utf8_to_uv_flags(s, e, &dummy, NULL, UTF8_WARN_NONCHAR);
                 ok = FALSE;
             }
         }