Index: doc/encoding.n
==================================================================
--- doc/encoding.n
+++ doc/encoding.n
@@ -12,20 +12,14 @@
 .SH SYNOPSIS
 \fBencoding \fIoption\fR ?\fIarg arg ...\fR?
 .BE
 .SH INTRODUCTION
 .PP
-Strings in Tcl are logically a sequence of 16-bit Unicode characters.
+Strings in Tcl are logically a sequence of Unicode characters.
 These strings are represented in memory as a sequence of bytes that
-may be in one of several encodings: modified UTF\-8 (which uses 1 to 3
-bytes per character), 16-bit
-.QW Unicode
-(which uses 2 bytes per character, with an endianness that is
-dependent on the host architecture), and binary (which uses a single
-byte per character but only handles a restricted range of characters).
-Tcl does not guarantee to always use the same encoding for the same
-string.
+may be in one of several encodings: modified UTF\-8 (which uses 1 to 4
+bytes per character), or a custom encoding start as 8 bit binary data.
 .PP
 Different operating system interfaces or applications may generate
 strings in other encodings such as Shift\-JIS.  The \fBencoding\fR
 command helps to bridge the gap between Unicode and these other
 formats.
@@ -32,27 +26,56 @@
 .SH DESCRIPTION
 .PP
 Performs one of several encoding related operations, depending on
 \fIoption\fR.  The legal \fIoption\fRs are:
 .TP
-\fBencoding convertfrom\fR ?\fIencoding\fR? \fIdata\fR
+\fBencoding convertfrom\fR ?\fB-nocomplain\fR? ?\fB-failindex var\fR?
+?\fIencoding\fR? \fIdata\fR
 .
-Convert \fIdata\fR to Unicode from the specified \fIencoding\fR.  The
-characters in \fIdata\fR are treated as binary data where the lower
-8-bits of each character is taken as a single byte.  The resulting
-sequence of bytes is treated as a string in the specified
-\fIencoding\fR.  If \fIencoding\fR is not specified, the current
+Convert \fIdata\fR to a Unicode string from the specified \fIencoding\fR.  The
+characters in \fIdata\fR are 8 bit binary data.  The resulting
+sequence of bytes is a string created by applying the given \fIencoding\fR
+to the data. If \fIencoding\fR is not specified, the current
 system encoding is used.
+.
+The call fails on convertion errors, like an incomplete utf-8 sequence.
+The option \fB-failindex\fR is followed by a variable name. The variable
+is set to \fI-1\fR if no conversion error occured. It is set to the
+first error location in \fIdata\fR in case of a conversion error. All data
+until this error location is transformed and retured. This option may not
+be used together with \fB-nocomplain\fR.
+.
+The call does not fail on conversion errors, if the option
+\fB-nocomplain\fR is given. In this case, any error locations are replaced
+by \fB?\fR. Incomplete sequences are written verbatim to the output string.
+The purpose of this switch is to gain compatibility to prior versions of TCL.
+It is not recommended for any other usage.
 .TP
-\fBencoding convertto\fR ?\fIencoding\fR? \fIstring\fR
+\fBencoding convertto\fR ?\fB-nocomplain\fR? ?\fB-failindex var\fR?
+?\fIencoding\fR? \fIstring\fR
 .
 Convert \fIstring\fR from Unicode to the specified \fIencoding\fR.
 The result is a sequence of bytes that represents the converted
 string.  Each byte is stored in the lower 8-bits of a Unicode
 character (indeed, the resulting string is a binary string as far as
 Tcl is concerned, at least initially).  If \fIencoding\fR is not
 specified, the current system encoding is used.
+.
+The call fails on convertion errors, like a Unicode character not representable
+in the given \fIencoding\fR.
+.
+The option \fB-failindex\fR is followed by a variable name. The variable
+is set to \fI-1\fR if no conversion error occured. It is set to the
+first error location in \fIdata\fR in case of a conversion error. All data
+until this error location is transformed and retured. This option may not
+be used together with \fB-nocomplain\fR.
+.
+The call does not fail on conversion errors, if the option
+\fB-nocomplain\fR is given. In this case, any error locations are replaced
+by \fB?\fR. Incomplete sequences are written verbatim to the output string.
+The purpose of this switch is to gain compatibility to prior versions of TCL.
+It is not recommended for any other usage.
 .TP
 \fBencoding dirs\fR ?\fIdirectoryList\fR?
 .
 Tcl can load encoding data files from the file system that describe
 additional encodings for it to work with. This command sets the search
@@ -88,12 +111,32 @@
 .CE
 .PP
 The result is the unicode codepoint:
 .QW "\eu306F" ,
 which is the Hiragana letter HA.
+.PP
+The following example detects the error location in an incomplete UTF-8 sequence:
+.PP
+.CS
+% set s [\fBencoding convertfrom\fR -failindex i utf-8 "A\xc3"]
+A
+% set i
+1
+.CE
+.PP
+The following example detects the error location while transforming to ISO8859-1
+(ISO-Latin 1):
+.PP
+.CS
+% set s [\fBencoding convertto\fR -failindex i utf-8 "A\u0141"]
+A
+% set i
+1
+.CE
+.PP
 .SH "SEE ALSO"
 Tcl_GetEncoding(3)
 .SH KEYWORDS
 encoding, unicode
 .\" Local Variables:
 .\" mode: nroff
 .\" End:

Index: generic/tclCmdAH.c
==================================================================
--- generic/tclCmdAH.c
+++ generic/tclCmdAH.c
@@ -554,40 +554,61 @@
     int flags = TCL_ENCODING_STOPONERROR;
 #else
     int flags = TCL_ENCODING_NOCOMPLAIN;
 #endif
     int result;
+    Tcl_Obj *failVarObj = NULL;
+    /*
+     * Decode parameters:
+     * Possible combinations:
+     * 1) data						-> objc = 2
+     * 2) encoding data					-> objc = 3
+     * 3) -nocomplain data				-> objc = 3
+     * 4) -nocomplain encoding data			-> objc = 4
+     * 5) -failindex val data				-> objc = 4
+     * 6) -failindex val encoding data			-> objc = 5
+     */
 
     if (objc == 2) {
 	encoding = Tcl_GetEncoding(interp, NULL);
 	data = objv[1];
-    } else if ((unsigned)(objc - 2) < 3) {
+    } else if (objc > 2 && objc < 6) {
+	int objcUnprocessed = objc;
 	data = objv[objc - 1];
 	bytesPtr = Tcl_GetString(objv[1]);
 	if (bytesPtr[0] == '-' && bytesPtr[1] == 'n'
 		&& !strncmp(bytesPtr, "-nocomplain", strlen(bytesPtr))) {
 	    flags = TCL_ENCODING_NOCOMPLAIN;
-	} else if (objc < 4) {
-	    if (Tcl_GetEncodingFromObj(interp, objv[objc - 2], &encoding) != TCL_OK) {
-		return TCL_ERROR;
-	    }
-	    goto encConvFromOK;
-	} else {
-	    goto encConvFromError;
-	}
-	if (objc < 4) {
-	    encoding = Tcl_GetEncoding(interp, NULL);
-	} else if (Tcl_GetEncodingFromObj(interp, objv[objc - 2], &encoding) != TCL_OK) {
-	    return TCL_ERROR;
+	    objcUnprocessed--;
+	} else if (bytesPtr[0] == '-' && bytesPtr[1] == 'f'
+		&& !strncmp(bytesPtr, "-failindex", strlen(bytesPtr))) {
+	    /* at least two additional arguments needed */
+	    if (objc < 4) {
+		goto encConvFromError;
+	    }
+	    failVarObj = objv[2];
+	    flags = TCL_ENCODING_STOPONERROR;
+	    objcUnprocessed -= 2;
+	}
+	switch (objcUnprocessed) {
+	    case 3:
+		if (Tcl_GetEncodingFromObj(interp, objv[objc - 2], &encoding) != TCL_OK) {
+		    return TCL_ERROR;
+		}
+		break;
+	    case 2:
+		encoding = Tcl_GetEncoding(interp, NULL);
+		break;
+	    default:
+		goto encConvFromError;
 	}
     } else {
     encConvFromError:
-	Tcl_WrongNumArgs(interp, 1, objv, "?-nocomplain? ?encoding? data");
+	Tcl_WrongNumArgs(interp, 1, objv, "?-nocomplain? ?-failindex var? ?encoding? data");
 	return TCL_ERROR;
     }
 
-encConvFromOK:
     /*
      * Convert the string into a byte array in 'ds'
      */
 #if !defined(TCL_NO_DEPRECATED) && (TCL_MAJOR_VERSION < 9)
     if (!(flags & TCL_ENCODING_STOPONERROR)) {
@@ -599,18 +620,28 @@
 	return TCL_ERROR;
     }
     result = Tcl_ExternalToUtfDStringEx(encoding, bytesPtr, length,
 	    flags, &ds);
     if (!(flags & TCL_ENCODING_NOCOMPLAIN) && (result != TCL_INDEX_NONE)) {
-	char buf[TCL_INTEGER_SPACE];
-	sprintf(buf, "%u", result);
-	Tcl_SetObjResult(interp, Tcl_ObjPrintf("unexpected byte sequence starting at index %"
-		"u: '\\x%X'", result, UCHAR(bytesPtr[result])));
-	Tcl_SetErrorCode(interp, "TCL", "ENCODING", "ILLEGALSEQUENCE",
-		buf, NULL);
-	Tcl_DStringFree(&ds);
-	return TCL_ERROR;
+	if (failVarObj != NULL) {
+	    if (Tcl_ObjSetVar2(interp, failVarObj, NULL, Tcl_NewWideIntObj(result), TCL_LEAVE_ERR_MSG) == NULL) {
+		return TCL_ERROR;
+	    }
+	} else {
+	    char buf[TCL_INTEGER_SPACE];
+	    sprintf(buf, "%u", result);
+	    Tcl_SetObjResult(interp, Tcl_ObjPrintf("unexpected byte sequence starting at index %"
+		    "u: '\\x%X'", result, UCHAR(bytesPtr[result])));
+	    Tcl_SetErrorCode(interp, "TCL", "ENCODING", "ILLEGALSEQUENCE",
+		    buf, NULL);
+	    Tcl_DStringFree(&ds);
+	    return TCL_ERROR;
+	}
+    } else if (failVarObj != NULL) {
+	if (Tcl_ObjSetVar2(interp, failVarObj, NULL, Tcl_NewIntObj(-1), TCL_LEAVE_ERR_MSG) == NULL) {
+	    return TCL_ERROR;
+	}
     }
 
     /*
      * Note that we cannot use Tcl_DStringResult here because it will
      * truncate the string at the first null byte.
@@ -657,59 +688,92 @@
 #if TCL_MAJOR_VERSION > 8 || defined(TCL_NO_DEPRECATED)
     int flags = TCL_ENCODING_STOPONERROR;
 #else
     int flags = TCL_ENCODING_NOCOMPLAIN;
 #endif
+    Tcl_Obj *failVarObj = NULL;
+
+    /*
+     * Decode parameters:
+     * Possible combinations:
+     * 1) data						-> objc = 2
+     * 2) encoding data					-> objc = 3
+     * 3) -nocomplain data				-> objc = 3
+     * 4) -nocomplain encoding data			-> objc = 4
+     * 5) -failindex val data				-> objc = 4
+     * 6) -failindex val encoding data			-> objc = 5
+     */
 
     if (objc == 2) {
 	encoding = Tcl_GetEncoding(interp, NULL);
 	data = objv[1];
-    } else if ((unsigned)(objc - 2) < 3) {
+    } else if (objc > 2 && objc < 6) {
+	int objcUnprocessed = objc;
 	data = objv[objc - 1];
 	stringPtr = Tcl_GetString(objv[1]);
 	if (stringPtr[0] == '-' && stringPtr[1] == 'n'
 		&& !strncmp(stringPtr, "-nocomplain", strlen(stringPtr))) {
 	    flags = TCL_ENCODING_NOCOMPLAIN;
-	} else if (objc < 4) {
-	    if (Tcl_GetEncodingFromObj(interp, objv[objc - 2], &encoding) != TCL_OK) {
-		return TCL_ERROR;
-	    }
-	    goto encConvToOK;
-	} else {
-	    goto encConvToError;
-	}
-	if (objc < 4) {
-	    encoding = Tcl_GetEncoding(interp, NULL);
-	} else if (Tcl_GetEncodingFromObj(interp, objv[objc - 2], &encoding) != TCL_OK) {
-	    return TCL_ERROR;
+	    objcUnprocessed--;
+	} else if (stringPtr[0] == '-' && stringPtr[1] == 'f'
+		&& !strncmp(stringPtr, "-failindex", strlen(stringPtr))) {
+	    /* at least two additional arguments needed */
+	    if (objc < 4) {
+		goto encConvToError;
+	    }
+	    failVarObj = objv[2];
+	    flags = TCL_ENCODING_STOPONERROR;
+	    objcUnprocessed -= 2;
+	}
+	switch (objcUnprocessed) {
+	    case 3:
+		if (Tcl_GetEncodingFromObj(interp, objv[objc - 2], &encoding) != TCL_OK) {
+		    return TCL_ERROR;
+		}
+		break;
+	    case 2:
+		encoding = Tcl_GetEncoding(interp, NULL);
+		break;
+	    default:
+		goto encConvToError;
 	}
     } else {
     encConvToError:
-	Tcl_WrongNumArgs(interp, 1, objv, "?-nocomplain? ?encoding? data");
+	Tcl_WrongNumArgs(interp, 1, objv, "?-nocomplain? ?-failindex var? ?encoding? data");
 	return TCL_ERROR;
     }
 
-encConvToOK:
     /*
      * Convert the string to a byte array in 'ds'
      */
 
     stringPtr = TclGetStringFromObj(data, &length);
     result = Tcl_UtfToExternalDStringEx(encoding, stringPtr, length,
 	    flags, &ds);
     if (!(flags & TCL_ENCODING_NOCOMPLAIN) && (result != TCL_INDEX_NONE)) {
-	int pos = Tcl_NumUtfChars(stringPtr, result);
-	int ucs4;
-	char buf[TCL_INTEGER_SPACE];
-	TclUtfToUCS4(&stringPtr[result], &ucs4);
-	sprintf(buf, "%u", result);
-	Tcl_SetObjResult(interp, Tcl_ObjPrintf("unexpected character at index %"
-		"u: 'U+%06X'", pos, ucs4));
-	Tcl_SetErrorCode(interp, "TCL", "ENCODING", "ILLEGALSEQUENCE",
-		buf, NULL);
-	Tcl_DStringFree(&ds);
-	return TCL_ERROR;
+	if (failVarObj != NULL) {
+	    /* I hope, wide int will cover size_t data type */
+	    if (Tcl_ObjSetVar2(interp, failVarObj, NULL, Tcl_NewWideIntObj(result), TCL_LEAVE_ERR_MSG) == NULL) {
+		return TCL_ERROR;
+	    }
+	} else {
+	    size_t pos = Tcl_NumUtfChars(stringPtr, result);
+	    int ucs4;
+	    char buf[TCL_INTEGER_SPACE];
+	    TclUtfToUCS4(&stringPtr[result], &ucs4);
+	    sprintf(buf, "%u", result);
+	    Tcl_SetObjResult(interp, Tcl_ObjPrintf("unexpected character at index %"
+		    TCL_Z_MODIFIER "u: 'U+%06X'", pos, ucs4));
+	    Tcl_SetErrorCode(interp, "TCL", "ENCODING", "ILLEGALSEQUENCE",
+		    buf, NULL);
+	    Tcl_DStringFree(&ds);
+	    return TCL_ERROR;
+	}
+    } else if (failVarObj != NULL) {
+	if (Tcl_ObjSetVar2(interp, failVarObj, NULL, Tcl_NewIntObj(-1), TCL_LEAVE_ERR_MSG) == NULL) {
+	    return TCL_ERROR;
+	}
     }
     Tcl_SetObjResult(interp,
 		     Tcl_NewByteArrayObj((unsigned char*) Tcl_DStringValue(&ds),
 					 Tcl_DStringLength(&ds)));
     Tcl_DStringFree(&ds);

Index: tests/cmdAH.test
==================================================================
--- tests/cmdAH.test
+++ tests/cmdAH.test
@@ -176,11 +176,11 @@
 test cmdAH-4.2 {Tcl_EncodingObjCmd} -returnCodes error -body {
     encoding foo
 } -result {unknown or ambiguous subcommand "foo": must be convertfrom, convertto, dirs, names, or system}
 test cmdAH-4.3 {Tcl_EncodingObjCmd} -returnCodes error -body {
     encoding convertto
-} -result {wrong # args: should be "encoding convertto ?-nocomplain? ?encoding? data"}
+} -result {wrong # args: should be "encoding convertto ?-nocomplain? ?-failindex var? ?encoding? data"}
 test cmdAH-4.4 {Tcl_EncodingObjCmd} -returnCodes error -body {
     encoding convertto foo bar
 } -result {unknown encoding "foo"}
 test cmdAH-4.5 {Tcl_EncodingObjCmd} -setup {
     set system [encoding system]
@@ -198,11 +198,11 @@
 } -cleanup {
     encoding system $system
 } -result 8C
 test cmdAH-4.7 {Tcl_EncodingObjCmd} -returnCodes error -body {
     encoding convertfrom
-} -result {wrong # args: should be "encoding convertfrom ?-nocomplain? ?encoding? data"}
+} -result {wrong # args: should be "encoding convertfrom ?-nocomplain? ?-failindex var? ?encoding? data"}
 test cmdAH-4.8 {Tcl_EncodingObjCmd} -returnCodes error -body {
     encoding convertfrom foo bar
 } -result {unknown encoding "foo"}
 test cmdAH-4.9 {Tcl_EncodingObjCmd} -setup {
     set system [encoding system]
@@ -232,10 +232,125 @@
     encoding system iso8859-1
     encoding system
 } -cleanup {
     encoding system $system
 } -result iso8859-1
+
+test cmdAH-4.14.1 {Syntax error, -nocomplain and -failindex, no encoding} -body {
+    encoding convertfrom -nocomplain -failindex 2 ABC
+} -returnCodes 1 -result {wrong # args: should be "encoding convertfrom ?-nocomplain? ?-failindex var? ?encoding? data"}
+test cmdAH-4.14.2 {Syntax error, -nocomplain and -failindex, no encoding} -body {
+    encoding convertto -nocomplain -failindex 2 ABC
+} -returnCodes 1 -result {wrong # args: should be "encoding convertto ?-nocomplain? ?-failindex var? ?encoding? data"}
+test cmdAH-4.15.1 {Syntax error, -failindex and -nocomplain, no encoding} -body {
+    encoding convertfrom -failindex 2 -nocomplain ABC
+} -returnCodes 1 -result {unknown encoding "-nocomplain"}
+test cmdAH-4.15.2 {Syntax error, -failindex and -nocomplain, no encoding} -body {
+    encoding convertto -failindex 2 -nocomplain ABC
+} -returnCodes 1 -result {unknown encoding "-nocomplain"}
+test cmdAH-4.16.1 {Syntax error, -nocomplain and -failindex, encoding} -body {
+    encoding convertfrom -nocomplain -failindex 2 utf-8 ABC
+} -returnCodes 1 -result {wrong # args: should be "encoding convertfrom ?-nocomplain? ?-failindex var? ?encoding? data"}
+test cmdAH-4.16.2 {Syntax error, -nocomplain and -failindex, encoding} -body {
+    encoding convertto -nocomplain -failindex 2 utf-8 ABC
+} -returnCodes 1 -result {wrong # args: should be "encoding convertto ?-nocomplain? ?-failindex var? ?encoding? data"}
+test cmdAH-4.17.1 {Syntax error, -failindex and -nocomplain, encoding} -body {
+    encoding convertfrom -failindex 2 -nocomplain utf-8 ABC
+} -returnCodes 1 -result {wrong # args: should be "encoding convertfrom ?-nocomplain? ?-failindex var? ?encoding? data"}
+test cmdAH-4.17.2 {Syntax error, -failindex and -nocomplain, encoding} -body {
+    encoding convertto -failindex 2 -nocomplain utf-8 ABC
+} -returnCodes 1 -result {wrong # args: should be "encoding convertto ?-nocomplain? ?-failindex var? ?encoding? data"}
+test cmdAH-4.18.1 {Syntax error, -failindex with no var, no encoding} -body {
+    encoding convertfrom -failindex ABC
+} -returnCodes 1 -result {wrong # args: should be "::tcl::encoding::convertfrom ?-nocomplain? ?-failindex var? ?encoding? data"}
+test cmdAH-4.18.2 {Syntax error, -failindex with no var, no encoding (byte compiled)} -setup {
+    proc encoding_test {} {
+        encoding convertfrom -failindex ABC
+    }
+} -body {
+    # Compile and execute
+    encoding_test
+} -returnCodes 1 -result {wrong # args: should be "::tcl::encoding::convertfrom ?-nocomplain? ?-failindex var? ?encoding? data"} -cleanup {
+    rename encoding_test ""
+}
+test cmdAH-4.18.3 {Syntax error, -failindex with no var, no encoding} -body {
+    encoding convertto -failindex ABC
+} -returnCodes 1 -result {wrong # args: should be "::tcl::encoding::convertto ?-nocomplain? ?-failindex var? ?encoding? data"}
+test cmdAH-4.18.4 {Syntax error, -failindex with no var, no encoding (byte compiled)} -setup {
+    proc encoding_test {} {
+        encoding convertto -failindex ABC
+    }
+} -body {
+    # Compile and execute
+    encoding_test
+} -returnCodes 1 -result {wrong # args: should be "::tcl::encoding::convertto ?-nocomplain? ?-failindex var? ?encoding? data"} -cleanup {
+    rename encoding_test ""
+}
+test cmdAH-4.19.1 {convertrom -failindex with correct data} -body {
+    encoding convertfrom -failindex test ABC
+    set test
+} -returnCodes 0 -result -1
+test cmdAH-4.19.2 {convertrom -failindex with correct data (byt compiled)} -setup {
+    proc encoding_test {} {
+	encoding convertfrom -failindex test ABC
+	set test
+    }
+} -body {
+    # Compile and execute
+    encoding_test
+} -returnCodes 0 -result -1 -cleanup {
+    rename encoding_test ""
+}
+test cmdAH-4.19.3 {convertrom -failindex with correct data} -body {
+    encoding convertto -failindex test ABC
+    set test
+} -returnCodes 0 -result -1
+test cmdAH-4.19.4 {convertrom -failindex with correct data (byt compiled)} -setup {
+    proc encoding_test {} {
+	encoding convertto -failindex test ABC
+	set test
+    }
+} -body {
+    # Compile and execute
+    encoding_test
+} -returnCodes 0 -result -1 -cleanup {
+    rename encoding_test ""
+}
+test cmdAH-4.20.1 {convertrom -failindex with incomplete utf8} -body {
+    set x [encoding convertfrom -failindex i utf-8 A\xc3]
+    binary scan $x H* y
+    list $y $i
+} -returnCodes 0 -result {41c3 -1}
+test cmdAH-4.20.2 {convertrom -failindex with incomplete utf8 (byte compiled)} -setup {
+    proc encoding_test {} {
+	set x [encoding convertfrom -failindex i utf-8 A\xc3]
+	binary scan $x H* y
+	list $y $i
+    }
+} -body {
+    # Compile and execute
+    encoding_test
+} -returnCodes 0 -result {41c3 -1} -cleanup {
+    rename encoding_test ""
+}
+test cmdAH-4.21.1 {convertto -failindex with wrong character} -body {
+    set x [encoding convertto -failindex i iso8859-1 A\u0141]
+    binary scan $x H* y
+    list $y $i
+} -returnCodes 0 -result {41 1}
+test cmdAH-4.21.2 {convertto -failindex with wrong character (byte compiled)} -setup {
+    proc encoding_test {} {
+    set x [encoding convertto -failindex i iso8859-1 A\u0141]
+	binary scan $x H* y
+	list $y $i
+    }
+} -body {
+    # Compile and execute
+    encoding_test
+} -returnCodes 0 -result {41 1} -cleanup {
+    rename encoding_test ""
+}
 
 test cmdAH-5.1 {Tcl_FileObjCmd} -returnCodes error -body {
     file
 } -result {wrong # args: should be "file subcommand ?arg ...?"}
 test cmdAH-5.2 {Tcl_FileObjCmd} -returnCodes error -body {

Index: tests/encoding.test
==================================================================
--- tests/encoding.test
+++ tests/encoding.test
@@ -667,14 +667,14 @@
 test encoding-24.21 {Parse with -nocomplain but without providing encoding} {
     string length [encoding convertto -nocomplain "\x20"]
 } 1
 test encoding-24.22 {Syntax error, two encodings} -body {
     encoding convertfrom iso8859-1 utf-8 "ZX\uD800"
-} -returnCodes 1 -result {wrong # args: should be "::tcl::encoding::convertfrom ?-nocomplain? ?encoding? data"}
+} -returnCodes 1 -result {wrong # args: should be "::tcl::encoding::convertfrom ?-nocomplain? ?-failindex var? ?encoding? data"}
 test encoding-24.23 {Syntax error, two encodings} -body {
     encoding convertto iso8859-1 utf-8 "ZX\uD800"
-} -returnCodes 1 -result {wrong # args: should be "::tcl::encoding::convertto ?-nocomplain? ?encoding? data"}
+} -returnCodes 1 -result {wrong # args: should be "::tcl::encoding::convertto ?-nocomplain? ?-failindex var? ?encoding? data"}
 
 file delete [file join [temporaryDirectory] iso2022.txt]
 
 #
 # Begin jajp encoding round-trip conformity tests

Index: tests/safe.test
==================================================================
--- tests/safe.test
+++ tests/safe.test
@@ -1267,20 +1267,20 @@
     set i [safe::interpCreate]
 } -body {
     interp eval $i encoding convertfrom
 } -returnCodes error -cleanup {
     safe::interpDelete $i
-} -result {wrong # args: should be "encoding convertfrom ?-nocomplain? ?encoding? data"}
+} -result {wrong # args: should be "encoding convertfrom ?-nocomplain? ?-failindex var? ?encoding? data"}
 test safe-11.7.1 {testing safe encoding} -setup {
     set i [safe::interpCreate]
 } -body {
     catch {interp eval $i encoding convertfrom} m o
     dict get $o -errorinfo
 } -returnCodes ok -match glob -cleanup {
     unset -nocomplain m o
     safe::interpDelete $i
-} -result {wrong # args: should be "encoding convertfrom ?-nocomplain? ?encoding? data"
+} -result {wrong # args: should be "encoding convertfrom ?-nocomplain? ?-failindex var? ?encoding? data"
     while executing
 "encoding convertfrom"
     invoked from within
 "encoding convertfrom"
     invoked from within
@@ -1289,20 +1289,20 @@
     set i [safe::interpCreate]
 } -body {
     interp eval $i encoding convertto
 } -returnCodes error -cleanup {
     safe::interpDelete $i
-} -result {wrong # args: should be "encoding convertto ?-nocomplain? ?encoding? data"}
+} -result {wrong # args: should be "encoding convertto ?-nocomplain? ?-failindex var? ?encoding? data"}
 test safe-11.8.1 {testing safe encoding} -setup {
     set i [safe::interpCreate]
 } -body {
     catch {interp eval $i encoding convertto} m o
     dict get $o -errorinfo
 } -returnCodes ok -match glob -cleanup {
     unset -nocomplain m o
     safe::interpDelete $i
-} -result {wrong # args: should be "encoding convertto ?-nocomplain? ?encoding? data"
+} -result {wrong # args: should be "encoding convertto ?-nocomplain? ?-failindex var? ?encoding? data"
     while executing
 "encoding convertto"
     invoked from within
 "encoding convertto"
     invoked from within