Taint more operands with case changes

 The documentation says that Perl taints certain operations when subject
 to locale rules, such as lc() and ucfirst().  Prior to this commit
 there were exceptions when the operand to these functions contained no
 characters whose case change actually varied depending on the locale,
 for example the empty string or above-Latin1 code points.  Changing to
 conform to the documentation simplifies the core code, and yields more
 consistent results.

10 files changed, 79 insertions, 108 deletions

diff --git a/embed.fnc b/embed.fnc
index 62faa21432..f324dd72b2 100644
--- a/embed.fnc
+++ b/embed.fnc
@@ -1512,13 +1512,17 @@ Ap	|void	|taint_proper	|NULLOK const char* f|NN const char *const s
 Apd	|UV	|to_utf8_case	|NN const U8 *p|NN U8* ustrp|NULLOK STRLEN *lenp \
 				|NN SV **swashp|NN const char *normal|NULLOK const char *special
 Abmd	|UV	|to_utf8_lower	|NN const U8 *p|NN U8* ustrp|NULLOK STRLEN *lenp
-AMp	|UV	|_to_utf8_lower_flags	|NN const U8 *p|NN U8* ustrp|NULLOK STRLEN *lenp|const bool flags|NULLOK bool* tainted_ptr
+AMp	|UV	|_to_utf8_lower_flags	|NN const U8 *p|NN U8* ustrp  \
+				|NULLOK STRLEN *lenp|const bool flags
 Abmd	|UV	|to_utf8_upper	|NN const U8 *p|NN U8* ustrp|NULLOK STRLEN *lenp
-AMp	|UV	|_to_utf8_upper_flags	|NN const U8 *p|NN U8* ustrp|NULLOK STRLEN *lenp|const bool flags|NULLOK bool* tainted_ptr
+AMp	|UV	|_to_utf8_upper_flags	|NN const U8 *p|NN U8* ustrp   \
+				|NULLOK STRLEN *lenp|const bool flags
 Abmd	|UV	|to_utf8_title	|NN const U8 *p|NN U8* ustrp|NULLOK STRLEN *lenp
-AMp	|UV	|_to_utf8_title_flags	|NN const U8 *p|NN U8* ustrp|NULLOK STRLEN *lenp|const bool flags|NULLOK bool* tainted_ptr
+AMp	|UV	|_to_utf8_title_flags	|NN const U8 *p|NN U8* ustrp   \
+				|NULLOK STRLEN *lenp|const bool flags
 Abmd	|UV	|to_utf8_fold	|NN const U8 *p|NN U8* ustrp|NULLOK STRLEN *lenp
-AMp	|UV	|_to_utf8_fold_flags|NN const U8 *p|NN U8* ustrp|NULLOK STRLEN *lenp|U8 flags|NULLOK bool* tainted_ptr
+AMp	|UV	|_to_utf8_fold_flags|NN const U8 *p|NN U8* ustrp       \
+				|NULLOK STRLEN *lenp|U8 flags
 #if defined(PERL_IN_MG_C) || defined(PERL_IN_PP_C)
 p	|bool	|translate_substr_offsets|STRLEN curlen|IV pos1_iv \
 					 |bool pos1_is_uv|IV len_iv \
diff --git a/embed.h b/embed.h
index 7a18084bb5..d1722482b0 100644
--- a/embed.h
+++ b/embed.h
@@ -35,10 +35,10 @@
 #define _is_utf8_perl_idcont(a)	Perl__is_utf8_perl_idcont(aTHX_ a)
 #define _is_utf8_perl_idstart(a)	Perl__is_utf8_perl_idstart(aTHX_ a)
 #define _to_uni_fold_flags(a,b,c,d)	Perl__to_uni_fold_flags(aTHX_ a,b,c,d)
-#define _to_utf8_fold_flags(a,b,c,d,e)	Perl__to_utf8_fold_flags(aTHX_ a,b,c,d,e)
-#define _to_utf8_lower_flags(a,b,c,d,e)	Perl__to_utf8_lower_flags(aTHX_ a,b,c,d,e)
-#define _to_utf8_title_flags(a,b,c,d,e)	Perl__to_utf8_title_flags(aTHX_ a,b,c,d,e)
-#define _to_utf8_upper_flags(a,b,c,d,e)	Perl__to_utf8_upper_flags(aTHX_ a,b,c,d,e)
+#define _to_utf8_fold_flags(a,b,c,d)	Perl__to_utf8_fold_flags(aTHX_ a,b,c,d)
+#define _to_utf8_lower_flags(a,b,c,d)	Perl__to_utf8_lower_flags(aTHX_ a,b,c,d)
+#define _to_utf8_title_flags(a,b,c,d)	Perl__to_utf8_title_flags(aTHX_ a,b,c,d)
+#define _to_utf8_upper_flags(a,b,c,d)	Perl__to_utf8_upper_flags(aTHX_ a,b,c,d)
 #define amagic_call(a,b,c,d)	Perl_amagic_call(aTHX_ a,b,c,d)
 #define amagic_deref_call(a,b)	Perl_amagic_deref_call(aTHX_ a,b)
 #define append_utf8_from_native_byte	S_append_utf8_from_native_byte
diff --git a/lib/locale.t b/lib/locale.t
index 3180a69833..8afbeab1cd 100644
--- a/lib/locale.t
+++ b/lib/locale.t
@@ -1873,17 +1873,19 @@ setlocale(&POSIX::LC_ALL, "C");
         my $above_latin1_case_change_delta; # Same for the specific ords > 255
                                             # that we use
 
-        # We test an ASCII character, which should change case and be tainted;
+        # We test an ASCII character, which should change case;
         # a Latin1 character, which shouldn't change case under this C locale,
-        #   and is tainted.
         # an above-Latin1 character that when the case is changed would cross
-        #   the 255/256 boundary, so doesn't change case and isn't tainted
-        # (the \x{149} is one of these, but changes into 2 characters, the
+        #   the 255/256 boundary, so doesn't change case
+        #   (the \x{149} is one of these, but changes into 2 characters, the
         #   first one of which doesn't cross the boundary.
         # the final one in each list is an above-Latin1 character whose case
-        #   does change, and shouldn't be tainted.  The code below uses its
-        #   position in its list as a marker to indicate that it, unlike the
-        #   other code points above ASCII, has a successful case change
+        #   does change.  The code below uses its position in its list as a
+        #   marker to indicate that it, unlike the other code points above
+        #   ASCII, has a successful case change
+        #
+        # All casing operations under locale (but not :not_characters) should
+        # taint
         if ($function =~ /^u/) {
             @list = ("", "a", "\xe0", "\xff", "\x{fb00}", "\x{149}", "\x{101}");
             $ascii_case_change_delta = -32;
@@ -1957,9 +1959,9 @@ setlocale(&POSIX::LC_ALL, "C");
                             : "; not encoded in utf8)")
                         . " should be \"$should_be\", got \"$changed\"");
 
-                    # Tainting shouldn't happen for utf8 locales, empty
-                    # strings, or those characters above 255.
-                    (! $is_utf8_locale && length($char) > 0 && ord($char) < 256)
+                    # Tainting shouldn't happen for use locale :not_character
+                    # (a utf8 locale)
+                    (! $is_utf8_locale)
                     ? check_taint($changed)
                     : check_taint_not($changed);
 
diff --git a/mathoms.c b/mathoms.c
index 592116a7ec..73f1e8d38b 100644
--- a/mathoms.c
+++ b/mathoms.c
@@ -1180,7 +1180,7 @@ Perl_to_utf8_fold(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp)
 {
     PERL_ARGS_ASSERT_TO_UTF8_FOLD;
 
-    return _to_utf8_fold_flags(p, ustrp, lenp, FOLD_FLAGS_FULL, NULL);
+    return _to_utf8_fold_flags(p, ustrp, lenp, FOLD_FLAGS_FULL);
 }
 
 UV
@@ -1188,7 +1188,7 @@ Perl_to_utf8_lower(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp)
 {
     PERL_ARGS_ASSERT_TO_UTF8_LOWER;
 
-    return _to_utf8_lower_flags(p, ustrp, lenp, FALSE, NULL);
+    return _to_utf8_lower_flags(p, ustrp, lenp, FALSE);
 }
 
 UV
@@ -1196,7 +1196,7 @@ Perl_to_utf8_title(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp)
 {
     PERL_ARGS_ASSERT_TO_UTF8_TITLE;
 
-    return _to_utf8_title_flags(p, ustrp, lenp, FALSE, NULL);
+    return _to_utf8_title_flags(p, ustrp, lenp, FALSE);
 }
 
 UV
@@ -1204,7 +1204,7 @@ Perl_to_utf8_upper(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp)
 {
     PERL_ARGS_ASSERT_TO_UTF8_UPPER;
 
-    return _to_utf8_upper_flags(p, ustrp, lenp, FALSE, NULL);
+    return _to_utf8_upper_flags(p, ustrp, lenp, FALSE);
 }
 
 SV *
diff --git a/pod/perldelta.pod b/pod/perldelta.pod
index 9d2a4aad05..5f88fa3f80 100644
--- a/pod/perldelta.pod
+++ b/pod/perldelta.pod
@@ -43,13 +43,16 @@ L</Selected Bug Fixes> section.
 
 =head1 Incompatible Changes
 
-XXX For a release on a stable branch, this section aspires to be:
-
-    There are no changes intentionally incompatible with 5.XXX.XXX
-    If any exist, they are bugs, and we request that you submit a
-    report.  See L</Reporting Bugs> below.
-
-[ List each incompatible change as a =head2 entry ]
+=head2 Tainting happens under more circumstances; now conforms to documentation
+
+When changing the case of a string (C<lc>, C<"\U">, I<etc>.), within the
+scope of C<use locale>, the result is now tainted no matter what the
+contents of the string were, as the documentation (L<perlsec>,
+L<perllocale/SECURITY>) indicates it should.   Previously, if the string
+contained no characters whose case change could be affected by the
+locale, the result would not be tainted.  For example, the result of
+C<uc()> on an empty string or one containing only above-Latin1 code
+points is now tainted.  This leads to more consistent tainting results.
 
 =head1 Deprecations
 
diff --git a/pp.c b/pp.c
index 22133b3834..c4117685c2 100644
--- a/pp.c
+++ b/pp.c
@@ -3479,7 +3479,6 @@ PP(pp_ucfirst)
     STRLEN tculen;  /* tculen is the byte length of the freshly titlecased (or
 		     * lowercased) character stored in tmpbuf.  May be either
 		     * UTF-8 or not, but in either case is the number of bytes */
-    bool tainted = FALSE;
 
     s = (const U8*)SvPV_const(source, slen);
 
@@ -3503,12 +3502,10 @@ PP(pp_ucfirst)
 	doing_utf8 = TRUE;
         ulen = UTF8SKIP(s);
         if (op_type == OP_UCFIRST) {
-	    _to_utf8_title_flags(s, tmpbuf, &tculen,
-				 IN_LOCALE_RUNTIME, &tainted);
+	    _to_utf8_title_flags(s, tmpbuf, &tculen, IN_LOCALE_RUNTIME);
 	}
         else {
-	    _to_utf8_lower_flags(s, tmpbuf, &tculen,
-				 IN_LOCALE_RUNTIME, &tainted);
+	    _to_utf8_lower_flags(s, tmpbuf, &tculen, IN_LOCALE_RUNTIME);
 	}
 
         /* we can't do in-place if the length changes.  */
@@ -3642,17 +3639,9 @@ PP(pp_ucfirst)
 	    SvCUR_set(dest, need - 1);
 	}
 
-	if (tainted) {
-	    TAINT;
-	    SvTAINTED_on(dest);
-	}
     }
     else {  /* Neither source nor dest are in or need to be UTF-8 */
 	if (slen) {
-	    if (IN_LOCALE_RUNTIME) {
-		TAINT;
-		SvTAINTED_on(dest);
-	    }
 	    if (inplace) {  /* in-place, only need to change the 1st char */
 		*d = *tmpbuf;
 	    }
@@ -3680,6 +3669,10 @@ PP(pp_ucfirst)
 	    SvCUR_set(dest, need - 1);
 	}
     }
+    if (IN_LOCALE_RUNTIME) {
+        TAINT;
+        SvTAINTED_on(dest);
+    }
     if (dest != source && SvTAINTED(source))
 	SvTAINT(dest);
     SvSETMAGIC(dest);
@@ -3740,7 +3733,6 @@ PP(pp_uc)
     if (DO_UTF8(source)) {
 	const U8 *const send = s + len;
 	U8 tmpbuf[UTF8_MAXBYTES_CASE+1];
-	bool tainted = FALSE;
 
 	/* All occurrences of these are to be moved to follow any other marks.
 	 * This is context-dependent.  We may not be passed enough context to
@@ -3770,8 +3762,7 @@ PP(pp_uc)
              * and copy it to the output buffer */
 
             u = UTF8SKIP(s);
-            uv = _to_utf8_upper_flags(s, tmpbuf, &ulen,
-				      IN_LOCALE_RUNTIME, &tainted);
+            uv = _to_utf8_upper_flags(s, tmpbuf, &ulen, IN_LOCALE_RUNTIME);
 #define GREEK_CAPITAL_LETTER_IOTA 0x0399
 #define COMBINING_GREEK_YPOGEGRAMMENI 0x0345
             if (uv == GREEK_CAPITAL_LETTER_IOTA
@@ -3806,10 +3797,6 @@ PP(pp_uc)
 	*d = '\0';
 
 	SvCUR_set(dest, d - (U8*)SvPVX_const(dest));
-	if (tainted) {
-	    TAINT;
-	    SvTAINTED_on(dest);
-	}
     }
     else {	/* Not UTF-8 */
 	if (len) {
@@ -3819,8 +3806,6 @@ PP(pp_uc)
 	     * latin1 as having case; otherwise the latin1 casing.  Do the
 	     * whole thing in a tight loop, for speed, */
 	    if (IN_LOCALE_RUNTIME) {
-		TAINT;
-		SvTAINTED_on(dest);
 		for (; s < send; d++, s++)
 		    *d = toUPPER_LC(*s);
 	    }
@@ -3918,6 +3903,10 @@ PP(pp_uc)
 	    SvCUR_set(dest, d - (U8*)SvPVX_const(dest));
 	}
     } /* End of isn't utf8 */
+    if (IN_LOCALE_RUNTIME) {
+        TAINT;
+        SvTAINTED_on(dest);
+    }
     if (dest != source && SvTAINTED(source))
 	SvTAINT(dest);
     SvSETMAGIC(dest);
@@ -3970,14 +3959,12 @@ PP(pp_lc)
     if (DO_UTF8(source)) {
 	const U8 *const send = s + len;
 	U8 tmpbuf[UTF8_MAXBYTES_CASE+1];
-	bool tainted = FALSE;
 
 	while (s < send) {
 	    const STRLEN u = UTF8SKIP(s);
 	    STRLEN ulen;
 
-	    _to_utf8_lower_flags(s, tmpbuf, &ulen,
-				 IN_LOCALE_RUNTIME, &tainted);
+	    _to_utf8_lower_flags(s, tmpbuf, &ulen, IN_LOCALE_RUNTIME);
 
 	    /* Here is where we would do context-sensitive actions.  See the
 	     * commit message for 86510fb15 for why there isn't any */
@@ -4007,10 +3994,6 @@ PP(pp_lc)
 	SvUTF8_on(dest);
 	*d = '\0';
 	SvCUR_set(dest, d - (U8*)SvPVX_const(dest));
-	if (tainted) {
-	    TAINT;
-	    SvTAINTED_on(dest);
-	}
     } else {	/* Not utf8 */
 	if (len) {
 	    const U8 *const send = s + len;
@@ -4018,12 +4001,10 @@ PP(pp_lc)
 	    /* Use locale casing if in locale; regular style if not treating
 	     * latin1 as having case; otherwise the latin1 casing.  Do the
 	     * whole thing in a tight loop, for speed, */
-	    if (IN_LOCALE_RUNTIME) {
-		TAINT;
-		SvTAINTED_on(dest);
+            if (IN_LOCALE_RUNTIME) {
 		for (; s < send; d++, s++)
 		    *d = toLOWER_LC(*s);
-	    }
+            }
 	    else if (! IN_UNI_8_BIT) {
 		for (; s < send; d++, s++) {
 		    *d = toLOWER(*s);
@@ -4040,6 +4021,10 @@ PP(pp_lc)
 	    SvCUR_set(dest, d - (U8*)SvPVX_const(dest));
 	}
     }
+    if (IN_LOCALE_RUNTIME) {
+        TAINT;
+        SvTAINTED_on(dest);
+    }
     if (dest != source && SvTAINTED(source))
 	SvTAINT(dest);
     SvSETMAGIC(dest);
@@ -4164,12 +4149,11 @@ PP(pp_fc)
 
     send = s + len;
     if (DO_UTF8(source)) { /* UTF-8 flagged string. */
-        bool tainted = FALSE;
         while (s < send) {
             const STRLEN u = UTF8SKIP(s);
             STRLEN ulen;
 
-            _to_utf8_fold_flags(s, tmpbuf, &ulen, flags, &tainted);
+            _to_utf8_fold_flags(s, tmpbuf, &ulen, flags);
 
             if (ulen > u && (SvLEN(dest) < (min += ulen - u))) {
                 const UV o = d - (U8*)SvPVX_const(dest);
@@ -4182,15 +4166,9 @@ PP(pp_fc)
             s += u;
         }
         SvUTF8_on(dest);
-	if (tainted) {
-	    TAINT;
-	    SvTAINTED_on(dest);
-	}
     } /* Unflagged string */
     else if (len) {
         if ( IN_LOCALE_RUNTIME ) { /* Under locale */
-            TAINT;
-            SvTAINTED_on(dest);
             for (; s < send; d++, s++)
                 *d = toFOLD_LC(*s);
         }
@@ -4265,6 +4243,10 @@ PP(pp_fc)
     *d = '\0';
     SvCUR_set(dest, d - (U8*)SvPVX_const(dest));
 
+    if (IN_LOCALE_RUNTIME) {
+        TAINT;
+        SvTAINTED_on(dest);
+    }
     if (SvTAINTED(source))
 	SvTAINT(dest);
     SvSETMAGIC(dest);
diff --git a/proto.h b/proto.h
index 6b36e5bf88..ec1550c1aa 100644
--- a/proto.h
+++ b/proto.h
@@ -81,25 +81,25 @@ PERL_CALLCONV UV	Perl__to_uni_fold_flags(pTHX_ UV c, U8 *p, STRLEN *lenp, const
 #define PERL_ARGS_ASSERT__TO_UNI_FOLD_FLAGS	\
 	assert(p); assert(lenp)
 
-PERL_CALLCONV UV	Perl__to_utf8_fold_flags(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp, U8 flags, bool* tainted_ptr)
+PERL_CALLCONV UV	Perl__to_utf8_fold_flags(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp, U8 flags)
 			__attribute__nonnull__(pTHX_1)
 			__attribute__nonnull__(pTHX_2);
 #define PERL_ARGS_ASSERT__TO_UTF8_FOLD_FLAGS	\
 	assert(p); assert(ustrp)
 
-PERL_CALLCONV UV	Perl__to_utf8_lower_flags(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp, const bool flags, bool* tainted_ptr)
+PERL_CALLCONV UV	Perl__to_utf8_lower_flags(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp, const bool flags)
 			__attribute__nonnull__(pTHX_1)
 			__attribute__nonnull__(pTHX_2);
 #define PERL_ARGS_ASSERT__TO_UTF8_LOWER_FLAGS	\
 	assert(p); assert(ustrp)
 
-PERL_CALLCONV UV	Perl__to_utf8_title_flags(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp, const bool flags, bool* tainted_ptr)
+PERL_CALLCONV UV	Perl__to_utf8_title_flags(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp, const bool flags)
 			__attribute__nonnull__(pTHX_1)
 			__attribute__nonnull__(pTHX_2);
 #define PERL_ARGS_ASSERT__TO_UTF8_TITLE_FLAGS	\
 	assert(p); assert(ustrp)
 
-PERL_CALLCONV UV	Perl__to_utf8_upper_flags(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp, const bool flags, bool* tainted_ptr)
+PERL_CALLCONV UV	Perl__to_utf8_upper_flags(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp, const bool flags)
 			__attribute__nonnull__(pTHX_1)
 			__attribute__nonnull__(pTHX_2);
 #define PERL_ARGS_ASSERT__TO_UTF8_UPPER_FLAGS	\
diff --git a/regexec.c b/regexec.c
index b8e709f426..0109370288 100644
--- a/regexec.c
+++ b/regexec.c
@@ -1268,7 +1268,7 @@ STMT_START {                               \
             uscan += len;                                                           \
             len=0;                                                                  \
         } else {                                                                    \
-            uvc = _to_utf8_fold_flags( (const U8*) uc, foldbuf, &foldlen, flags, NULL);                \
+            uvc = _to_utf8_fold_flags( (const U8*) uc, foldbuf, &foldlen, flags);   \
             len = UTF8SKIP(uc);                                                     \
             skiplen = UNISKIP( uvc );                                               \
             foldlen -= skiplen;                                                     \
diff --git a/utf8.c b/utf8.c
index deb7a6d1cb..9f3a219585 100644
--- a/utf8.c
+++ b/utf8.c
@@ -1805,7 +1805,7 @@ Perl__to_uni_fold_flags(pTHX_ UV c, U8* p, STRLEN *lenp, const U8 flags)
 	       the special flags. */
 	U8 utf8_c[UTF8_MAXBYTES + 1];
 	uvchr_to_utf8(utf8_c, c);
-	return _to_utf8_fold_flags(utf8_c, p, lenp, flags, NULL);
+	return _to_utf8_fold_flags(utf8_c, p, lenp, flags);
     }
 }
 
@@ -2138,12 +2138,10 @@ Instead use L</toUPPER_utf8>.
 =cut */
 
 /* Not currently externally documented, and subject to change:
- * <flags> is set iff locale semantics are to be used for code points < 256
- * <tainted_ptr> if non-null, *tainted_ptr will be set TRUE iff locale rules
- *		 were used in the calculation; otherwise unchanged. */
+ * <flags> is set iff locale semantics are to be used for code points < 256 */
 
 UV
-Perl__to_utf8_upper_flags(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp, const bool flags, bool* tainted_ptr)
+Perl__to_utf8_upper_flags(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp, const bool flags)
 {
     dVAR;
 
@@ -2188,10 +2186,6 @@ Perl__to_utf8_upper_flags(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp, const bool
 	*(ustrp + 1) = UTF8_EIGHT_BIT_LO((U8) result);
 	*lenp = 2;
     }
-
-    if (tainted_ptr) {
-	*tainted_ptr = TRUE;
-    }
     return result;
 }
 
@@ -2206,11 +2200,10 @@ Instead use L</toTITLE_utf8>.
  * <flags> is set iff locale semantics are to be used for code points < 256
  *	   Since titlecase is not defined in POSIX, uppercase is used instead
  *	   for these/
- * <tainted_ptr> if non-null, *tainted_ptr will be set TRUE iff locale rules
- *		 were used in the calculation; otherwise unchanged. */
+ */
 
 UV
-Perl__to_utf8_title_flags(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp, const bool flags, bool* tainted_ptr)
+Perl__to_utf8_title_flags(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp, const bool flags)
 {
     dVAR;
 
@@ -2256,9 +2249,6 @@ Perl__to_utf8_title_flags(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp, const bool
 	*lenp = 2;
     }
 
-    if (tainted_ptr) {
-	*tainted_ptr = TRUE;
-    }
     return result;
 }
 
@@ -2270,12 +2260,10 @@ Instead use L</toLOWER_utf8>.
 =cut */
 
 /* Not currently externally documented, and subject to change:
- * <flags> is set iff locale semantics are to be used for code points < 256
- * <tainted_ptr> if non-null, *tainted_ptr will be set TRUE iff locale rules
- *		 were used in the calculation; otherwise unchanged. */
+ * <flags> is set iff locale semantics are to be used for code points < 256 */
 
 UV
-Perl__to_utf8_lower_flags(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp, const bool flags, bool* tainted_ptr)
+Perl__to_utf8_lower_flags(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp, const bool flags)
 {
     UV result;
 
@@ -2322,9 +2310,6 @@ Perl__to_utf8_lower_flags(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp, const bool
 	*lenp = 2;
     }
 
-    if (tainted_ptr) {
-	*tainted_ptr = TRUE;
-    }
     return result;
 }
 
@@ -2344,11 +2329,10 @@ Instead use L</toFOLD_utf8>.
  *			      otherwise simple folds
  *      bit FOLD_FLAGS_NOMIX_ASCII is set iff folds of non-ASCII to ASCII are
  *			      prohibited
- * <tainted_ptr> if non-null, *tainted_ptr will be set TRUE iff locale rules
- *		 were used in the calculation; otherwise unchanged. */
+ */
 
 UV
-Perl__to_utf8_fold_flags(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp, U8 flags, bool* tainted_ptr)
+Perl__to_utf8_fold_flags(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp, U8 flags)
 {
     dVAR;
 
@@ -2453,9 +2437,6 @@ Perl__to_utf8_fold_flags(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp, U8 flags, b
 	*lenp = 2;
     }
 
-    if (tainted_ptr) {
-	*tainted_ptr = TRUE;
-    }
     return result;
 
   return_long_s:
diff --git a/utf8.h b/utf8.h
index f72a2433cc..09e4f7c5f4 100644
--- a/utf8.h
+++ b/utf8.h
@@ -47,11 +47,10 @@
                                     ckWARN_d(WARN_UTF8) ? 0 : UTF8_ALLOW_ANY)
 
 #define to_uni_fold(c, p, lenp) _to_uni_fold_flags(c, p, lenp, FOLD_FLAGS_FULL)
-#define to_utf8_fold(c, p, lenp) _to_utf8_fold_flags(c, p, lenp, \
-	             FOLD_FLAGS_FULL, NULL)
-#define to_utf8_lower(a,b,c) _to_utf8_lower_flags(a,b,c,0, NULL)
-#define to_utf8_upper(a,b,c) _to_utf8_upper_flags(a,b,c,0, NULL)
-#define to_utf8_title(a,b,c) _to_utf8_title_flags(a,b,c,0, NULL)
+#define to_utf8_fold(c, p, lenp) _to_utf8_fold_flags(c, p, lenp, FOLD_FLAGS_FULL)
+#define to_utf8_lower(a,b,c) _to_utf8_lower_flags(a,b,c,0)
+#define to_utf8_upper(a,b,c) _to_utf8_upper_flags(a,b,c,0)
+#define to_utf8_title(a,b,c) _to_utf8_title_flags(a,b,c,0)
 
 /* Source backward compatibility. */
 #define is_utf8_string_loc(s, len, ep)	is_utf8_string_loclen(s, len, ep, 0)