Merge rest of 8.7 except the botched apply/backout dance.

6 files changed, 346 insertions, 174 deletions

diff --git a/generic/tclCmdMZ.c b/generic/tclCmdMZ.c
index ba96d7c..0b65758 100644
--- a/generic/tclCmdMZ.c
+++ b/generic/tclCmdMZ.c
@@ -2305,7 +2305,6 @@ StringRplcCmd(
     int objc,			/* Number of arguments. */
     Tcl_Obj *const objv[])	/* Argument objects. */
 {
-    Tcl_UniChar *ustring;
     int first, last, length, end;
 
     if (objc < 4 || objc > 5) {
@@ -2313,7 +2312,7 @@ StringRplcCmd(
 	return TCL_ERROR;
     }
 
-    ustring = Tcl_GetUnicodeFromObj(objv[1], &length);
+    length = Tcl_GetCharLength(objv[1]);
     end = length - 1;
 
     if (TclGetIntForIndexM(interp, objv[2], end, &first) != TCL_OK ||
@@ -2339,26 +2338,17 @@ StringRplcCmd(
     } else {
 	Tcl_Obj *resultPtr;
 
-	/*
-	 * We are re-fetching in case the string argument is same value as 
-	 * an index argument, and shimmering cost us our ustring.
-	 */
-
-	ustring = Tcl_GetUnicodeFromObj(objv[1], &length);
-	end = length-1;
-
 	if (first < 0) {
 	    first = 0;
 	}
-
-	resultPtr = Tcl_NewUnicodeObj(ustring, first);
-	if (objc == 5) {
-	    Tcl_AppendObjToObj(resultPtr, objv[4]);
-	}
-	if (last < end) {
-	    Tcl_AppendUnicodeToObj(resultPtr, ustring + last + 1,
-		    end - last);
+	if (last > end) {
+	    last = end;
 	}
+
+	resultPtr = TclStringReplace(interp, objv[1], first,
+		last + 1 - first, (objc == 5) ? objv[4] : NULL,
+		TCL_STRING_IN_PLACE);
+
 	Tcl_SetObjResult(interp, resultPtr);
     }
     return TCL_OK;
@@ -3228,8 +3218,7 @@ StringTrimCmd(
     }
     string1 = TclGetStringFromObj(objv[1], &length1);
 
-    triml = TclTrimLeft(string1, length1, string2, length2);
-    trimr = TclTrimRight(string1 + triml, length1 - triml, string2, length2);
+    triml = TclTrim(string1, length1, string2, length2, &trimr);
 
     Tcl_SetObjResult(interp,
 	    Tcl_NewStringObj(string1 + triml, length1 - triml - trimr));
diff --git a/generic/tclExecute.c b/generic/tclExecute.c
index 59f6826..f294272 100644
--- a/generic/tclExecute.c
+++ b/generic/tclExecute.c
@@ -5467,82 +5467,9 @@ TEBCresume(
 	    NEXT_INST_F(1, 0, 0);
 	}
 
-	length3 = Tcl_GetCharLength(value3Ptr);
+	objResultPtr = TclStringReplace(interp, valuePtr, fromIdx,
+		toIdx - fromIdx + 1, value3Ptr, TCL_STRING_IN_PLACE);
 
-	/*
-	 * See if we can splice in place. This happens when the number of
-	 * characters being replaced is the same as the number of characters
-	 * in the string to be inserted.
-	 */
-
-	if (length3 - 1 == toIdx - fromIdx) {
-	    unsigned char *bytes1, *bytes2;
-
-	    if (Tcl_IsShared(valuePtr)) {
-		objResultPtr = Tcl_DuplicateObj(valuePtr);
-	    } else {
-		objResultPtr = valuePtr;
-	    }
-	    if (TclIsPureByteArray(objResultPtr)
-		    && TclIsPureByteArray(value3Ptr)) {
-		bytes1 = Tcl_GetByteArrayFromObj(objResultPtr, NULL);
-		bytes2 = Tcl_GetByteArrayFromObj(value3Ptr, NULL);
-		memcpy(bytes1 + fromIdx, bytes2, length3);
-	    } else {
-		ustring1 = Tcl_GetUnicodeFromObj(objResultPtr, NULL);
-		ustring2 = Tcl_GetUnicodeFromObj(value3Ptr, NULL);
-		memcpy(ustring1 + fromIdx, ustring2,
-			length3 * sizeof(Tcl_UniChar));
-	    }
-	    Tcl_InvalidateStringRep(objResultPtr);
-	    TclDecrRefCount(value3Ptr);
-	    TRACE_APPEND(("\"%.30s\"\n", O2S(objResultPtr)));
-	    if (objResultPtr == valuePtr) {
-		NEXT_INST_F(1, 0, 0);
-	    } else {
-		NEXT_INST_F(1, 1, 1);
-	    }
-	}
-
-	/*
-	 * Get the unicode representation; this is where we guarantee to lose
-	 * bytearrays.
-	 */
-
-	ustring1 = Tcl_GetUnicodeFromObj(valuePtr, &length);
-	length--;
-
-	/*
-	 * Remove substring using copying.
-	 */
-
-	objResultPtr = NULL;
-	if (fromIdx > 0) {
-	    objResultPtr = Tcl_NewUnicodeObj(ustring1, fromIdx);
-	}
-	if (length3 > 0) {
-	    if (objResultPtr) {
-		Tcl_AppendObjToObj(objResultPtr, value3Ptr);
-	    } else if (Tcl_IsShared(value3Ptr)) {
-		objResultPtr = Tcl_DuplicateObj(value3Ptr);
-	    } else {
-		objResultPtr = value3Ptr;
-	    }
-	}
-	if (toIdx < length) {
-	    if (objResultPtr) {
-		Tcl_AppendUnicodeToObj(objResultPtr, ustring1 + toIdx + 1,
-			length - toIdx);
-	    } else {
-		objResultPtr = Tcl_NewUnicodeObj(ustring1 + toIdx + 1,
-			length - toIdx);
-	    }
-	}
-	if (objResultPtr == NULL) {
-	    /* This has to be the case [string replace $s 0 end {}] */
-	    /* which has result {} which is same as value3Ptr. */
-	    objResultPtr = value3Ptr;
-	}
 	if (objResultPtr == value3Ptr) {
 	    /* See [Bug 82e7f67325] */
 	    TclDecrRefCount(OBJ_AT_TOS);
@@ -5717,12 +5644,7 @@ TEBCresume(
 	value2Ptr = OBJ_AT_TOS;		/* TrimSet */
 	string2 = TclGetStringFromObj(value2Ptr, &length2);
 	string1 = TclGetStringFromObj(valuePtr, &length);
-	trim1 = TclTrimLeft(string1, length, string2, length2);
-	if (trim1 < length) {
-	    trim2 = TclTrimRight(string1, length, string2, length2);
-	} else {
-	    trim2 = 0;
-	}
+	trim1 = TclTrim(string1, length, string2, length2, &trim2);
     createTrimmedString:
 	/*
 	 * Careful here; trim set often contains non-ASCII characters so we
diff --git a/generic/tclInt.h b/generic/tclInt.h
index e7794c7..81b1c05 100644
--- a/generic/tclInt.h
+++ b/generic/tclInt.h
@@ -3198,6 +3198,8 @@ MODULE_SCOPE void	TclSubstParse(Tcl_Interp *interp, const char *bytes,
 MODULE_SCOPE int	TclSubstTokens(Tcl_Interp *interp, Tcl_Token *tokenPtr,
 			    int count, int *tokensLeftPtr, int line,
 			    int *clNextOuter, const char *outerScript);
+MODULE_SCOPE int	TclTrim(const char *bytes, int numBytes,
+			    const char *trim, int numTrim, int *trimRight);
 MODULE_SCOPE int	TclTrimLeft(const char *bytes, int numBytes,
 			    const char *trim, int numTrim);
 MODULE_SCOPE int	TclTrimRight(const char *bytes, int numBytes,
@@ -4004,6 +4006,9 @@ MODULE_SCOPE int	TclStringLast(Tcl_Obj *needle, Tcl_Obj *haystack,
 			    int last);
 MODULE_SCOPE Tcl_Obj *	TclStringRepeat(Tcl_Interp *interp, Tcl_Obj *objPtr,
 			    int count, int flags);
+MODULE_SCOPE Tcl_Obj *	TclStringReplace(Tcl_Interp *interp, Tcl_Obj *objPtr,
+			    int first, int count, Tcl_Obj *insertPtr,
+			    int flags);
 MODULE_SCOPE Tcl_Obj *	TclStringReverse(Tcl_Obj *objPtr, int flags);
 
 /* Flag values for the [string] ensemble functions. */
diff --git a/generic/tclProcess.c b/generic/tclProcess.c
index 8d98a23..7187ee4 100644
--- a/generic/tclProcess.c
+++ b/generic/tclProcess.c
@@ -210,7 +210,7 @@ WaitProcessStatus(
     const char *msg;
 
     pid = Tcl_WaitPid(pid, &waitStatus, options);
-    if ((pid == 0)) {
+    if (pid == 0) {
 	/*
 	 * No change.
 	 */
diff --git a/generic/tclStringObj.c b/generic/tclStringObj.c
index 26a3a28..9913160 100644
--- a/generic/tclStringObj.c
+++ b/generic/tclStringObj.c
@@ -38,6 +38,7 @@
 #include "tommath.h"
 #include "tclStringRep.h"
 
+#include "assert.h"
 /*
  * Prototypes for functions defined later in this file:
  */
@@ -3531,6 +3532,150 @@ TclStringReverse(
 /*
  *---------------------------------------------------------------------------
  *
+ * TclStringReplace --
+ *
+ *	Implements the inner engine of the [string replace] command.
+ *
+ *	The result is a concatenation of a prefix from objPtr, characters
+ *	0 through first-1, the insertPtr string value, and a suffix from
+ *	objPtr, characters from first + count to the end. The effect is
+ *	as if the inner substring of characters first through first+count-1
+ *	are removed and replaced with insertPtr.
+ *	If insertPtr is NULL, it is treated as an empty string.
+ *	When passed the flag TCL_STRING_IN_PLACE, this routine will try
+ *	to do the work within objPtr, so long as no sharing forbids it.
+ *	Without that request, or as needed, a new Tcl value will be allocated
+ *	to be the result.
+ *
+ * Results:
+ *	A Tcl value that is the result of the substring replacement.
+ *	May return NULL in case of an error. When NULL is returned and
+ *	interp is non-NULL, error information is left in interp
+ *
+ *---------------------------------------------------------------------------
+ */
+
+Tcl_Obj *
+TclStringReplace(
+    Tcl_Interp *interp,		/* For error reporting, may be NULL */
+    Tcl_Obj *objPtr,		/* String to act upon */
+    int first,			/* First index to replace */
+    int count,			/* How many chars to replace */
+    Tcl_Obj *insertPtr,		/* Replacement string, may be NULL */
+    int flags)			/* TCL_STRING_IN_PLACE => attempt in-place */
+{
+    int inPlace = flags & TCL_STRING_IN_PLACE;
+    Tcl_Obj *result;
+
+    /* Caller is expected to pass sensible arguments */
+    assert ( count >= 0 ) ;
+    assert ( first >= 0 ) ;
+
+    /* Replace nothing with nothing */
+    if ((insertPtr == NULL) && (count == 0)) {
+	if (inPlace) {
+	    return objPtr;
+	} else {
+	    return Tcl_DuplicateObj(objPtr);
+	}
+    }
+
+    /*
+     * The caller very likely had to call Tcl_GetCharLength() or similar
+     * to be able to process index values.  This means it is like that
+     * objPtr is either a proper "bytearray" or a "string" or else it has
+     * a known and short string rep.
+     */
+
+    if (TclIsPureByteArray(objPtr)) {
+	int numBytes;
+	unsigned char *bytes = Tcl_GetByteArrayFromObj(objPtr, &numBytes);
+
+	if (insertPtr == NULL) {
+	    /* Replace something with nothing. */
+
+	    assert ( first <= numBytes ) ;
+	    assert ( count <= numBytes ) ;
+	    assert ( first + count <= numBytes ) ;
+
+	    result = Tcl_NewByteArrayObj(NULL, numBytes - count);/* PANIC? */
+	    TclAppendBytesToByteArray(result, bytes, first);
+	    TclAppendBytesToByteArray(result, bytes + first + count,
+		    numBytes - count - first);
+	    return result;
+	}
+
+	/* Replace everything */
+	if ((first == 0) && (count == numBytes)) {
+	    return insertPtr;
+	}
+
+	if (TclIsPureByteArray(insertPtr)) {
+	    int newBytes;
+	    unsigned char *iBytes
+		    = Tcl_GetByteArrayFromObj(insertPtr, &newBytes);
+
+	    if (count == newBytes && inPlace && !Tcl_IsShared(objPtr)) {
+		/*
+		 * Removal count and replacement count are equal.
+		 * Other conditions permit. Do in-place splice.
+		 */
+
+		memcpy(bytes + first, iBytes, count);
+		Tcl_InvalidateStringRep(objPtr);
+		return objPtr;
+	    }
+
+	    if (newBytes > INT_MAX - (numBytes - count)) {
+		if (interp) {
+		    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+			    "max size for a Tcl value (%d bytes) exceeded",
+			    INT_MAX));
+		    Tcl_SetErrorCode(interp, "TCL", "MEMORY", NULL);
+		}
+		return NULL;
+	    }
+	    result = Tcl_NewByteArrayObj(NULL, numBytes - count + newBytes);
+								/* PANIC? */
+	    TclAppendBytesToByteArray(result, bytes, first);	
+	    TclAppendBytesToByteArray(result, iBytes, newBytes);
+	    TclAppendBytesToByteArray(result, bytes + first + count,
+		    numBytes - count - first);
+	    return result;
+	}
+
+	/* Flow through to try other approaches below */
+    }
+
+    /*
+     * TODO: Figure out how not to generate a Tcl_UniChar array rep
+     * when it can be determined objPtr->bytes points to a string of
+     * all single-byte characters so we can index it directly.
+     */
+
+    /* The traditional implementation... */
+    {
+	int numChars;
+	Tcl_UniChar *ustring = Tcl_GetUnicodeFromObj(objPtr, &numChars);
+
+	/* TODO: Is there an in-place option worth pursuing here? */
+	
+	result = Tcl_NewUnicodeObj(ustring, first);
+	if (insertPtr) {
+	    Tcl_AppendObjToObj(result, insertPtr);
+	}
+	if (first + count < numChars) {
+	    Tcl_AppendUnicodeToObj(result, ustring + first + count,
+		    numChars - first - count);
+	}
+
+	return result;
+    }
+}
+
+/*
+ *---------------------------------------------------------------------------
+ *
  * FillUnicodeRep --
  *
  *	Populate the Unicode internal rep with the Unicode form of its string
diff --git a/generic/tclUtil.c b/generic/tclUtil.c
index d1b81a9..0ba6c8e 100644
--- a/generic/tclUtil.c
+++ b/generic/tclUtil.c
@@ -1647,11 +1647,46 @@ Tcl_Backslash(
 /*
  *----------------------------------------------------------------------
  *
- * TclTrimRight --
+ * UtfWellFormedEnd --
+ *	Checks the end of utf string is malformed, if yes - wraps bytes
+ *	to the given buffer (as well-formed NTS string).  The buffer
+ *	argument should be initialized by the caller and ready to use.
+ *
+ * Results:
+ *	The bytes with well-formed end of the string.
  *
- *	Takes two counted strings in the Tcl encoding which must both be null
- *	terminated. Conceptually trims from the right side of the first string
- *	all characters found in the second string.
+ * Side effects:
+ *	Buffer (DString) may be allocated, so must be released.
+ *
+ *----------------------------------------------------------------------
+ */
+
+static inline const char*
+UtfWellFormedEnd(
+    Tcl_DString *buffer,	/* Buffer used to hold well-formed string. */
+    const char *bytes,		/* Pointer to the beginning of the string. */
+    int length)			/* Length of the string. */
+{
+    const char *l = bytes + length;
+    const char *p = Tcl_UtfPrev(l, bytes);
+
+    if (Tcl_UtfCharComplete(p, l - p)) {
+	return bytes;
+    }
+    /* 
+     * Malformed utf-8 end, be sure we've NTS to safe compare of end-character,
+     * avoid segfault by access violation out of range.
+     */
+    Tcl_DStringAppend(buffer, bytes, length);
+    return Tcl_DStringValue(buffer);
+}
+/*
+ *----------------------------------------------------------------------
+ *
+ * TclTrimRight --
+ *	Takes two counted strings in the Tcl encoding.  Conceptually
+ *	finds the sub string (offset) to trim from the right side of the
+ *	first string all characters found in the second string.
  *
  * Results:
  *	The number of bytes to be removed from the end of the string.
@@ -1662,8 +1697,8 @@ Tcl_Backslash(
  *----------------------------------------------------------------------
  */
 
-int
-TclTrimRight(
+static inline int
+TrimRight(
     const char *bytes,		/* String to be trimmed... */
     int numBytes,		/* ...and its length in bytes */
     const char *trim,		/* String of trim characters... */
@@ -1673,18 +1708,6 @@ TclTrimRight(
     int pInc;
     Tcl_UniChar ch1 = 0, ch2 = 0;
 
-    if ((bytes[numBytes] != '\0') || (trim[numTrim] != '\0')) {
-	Tcl_Panic("TclTrimRight works only on null-terminated strings");
-    }
-
-    /*
-     * Empty strings -> nothing to do.
-     */
-
-    if ((numBytes == 0) || (numTrim == 0)) {
-	return 0;
-    }
-
     /*
      * Outer loop: iterate over string to be trimmed.
      */
@@ -1723,15 +1746,46 @@ TclTrimRight(
 
     return numBytes - (p - bytes);
 }
+
+int
+TclTrimRight(
+    const char *bytes,	/* String to be trimmed... */
+    int numBytes,	/* ...and its length in bytes */
+    const char *trim,	/* String of trim characters... */
+    int numTrim)	/* ...and its length in bytes */
+{
+    int res;
+    Tcl_DString bytesBuf, trimBuf;
+
+    /* Empty strings -> nothing to do */
+    if ((numBytes == 0) || (numTrim == 0)) {
+	return 0;
+    }
+
+    Tcl_DStringInit(&bytesBuf);
+    Tcl_DStringInit(&trimBuf);
+    bytes = UtfWellFormedEnd(&bytesBuf, bytes, numBytes);
+    trim = UtfWellFormedEnd(&trimBuf, trim, numTrim);
+
+    res = TrimRight(bytes, numBytes, trim, numTrim);
+    if (res > numBytes) {
+	res = numBytes;
+    }
+
+    Tcl_DStringFree(&bytesBuf);
+    Tcl_DStringFree(&trimBuf);
+
+    return res;
+}
 
 /*
  *----------------------------------------------------------------------
  *
  * TclTrimLeft --
  *
- *	Takes two counted strings in the Tcl encoding which must both be null
- *	terminated. Conceptually trims from the left side of the first string
- *	all characters found in the second string.
+ *	Takes two counted strings in the Tcl encoding.  Conceptually
+ *	finds the sub string (offset) to trim from the left side of the
+ *	first string all characters found in the second string.
  *
  * Results:
  *	The number of bytes to be removed from the start of the string.
@@ -1742,8 +1796,8 @@ TclTrimRight(
  *----------------------------------------------------------------------
  */
 
-int
-TclTrimLeft(
+static inline int
+TrimLeft(
     const char *bytes,		/* String to be trimmed... */
     int numBytes,		/* ...and its length in bytes */
     const char *trim,		/* String of trim characters... */
@@ -1752,18 +1806,6 @@ TclTrimLeft(
     const char *p = bytes;
 	Tcl_UniChar ch1 = 0, ch2 = 0;
 
-    if ((bytes[numBytes] != '\0') || (trim[numTrim] != '\0')) {
-	Tcl_Panic("TclTrimLeft works only on null-terminated strings");
-    }
-
-    /*
-     * Empty strings -> nothing to do.
-     */
-
-    if ((numBytes == 0) || (numTrim == 0)) {
-	return 0;
-    }
-
     /*
      * Outer loop: iterate over string to be trimmed.
      */
@@ -1798,10 +1840,99 @@ TclTrimLeft(
 
 	p += pInc;
 	numBytes -= pInc;
-    } while (numBytes);
+    } while (numBytes > 0);
 
     return p - bytes;
 }
+
+int
+TclTrimLeft(
+    const char *bytes,	/* String to be trimmed... */
+    int numBytes,	/* ...and its length in bytes */
+    const char *trim,	/* String of trim characters... */
+    int numTrim)	/* ...and its length in bytes */
+{
+    int res;
+    Tcl_DString bytesBuf, trimBuf;
+
+    /* Empty strings -> nothing to do */
+    if ((numBytes == 0) || (numTrim == 0)) {
+	return 0;
+    }
+
+    Tcl_DStringInit(&bytesBuf);
+    Tcl_DStringInit(&trimBuf);
+    bytes = UtfWellFormedEnd(&bytesBuf, bytes, numBytes);
+    trim = UtfWellFormedEnd(&trimBuf, trim, numTrim);
+
+    res = TrimLeft(bytes, numBytes, trim, numTrim);
+    if (res > numBytes) {
+	res = numBytes;
+    }
+
+    Tcl_DStringFree(&bytesBuf);
+    Tcl_DStringFree(&trimBuf);
+
+    return res;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * TclTrim --
+ *	Finds the sub string (offset) to trim from both sides of the
+ *	first string all characters found in the second string.
+ *
+ * Results:
+ *	The number of bytes to be removed from the start of the string
+ *
+ * Side effects:
+ *	None.
+ *
+ *----------------------------------------------------------------------
+ */
+
+int
+TclTrim(
+    const char *bytes,	/* String to be trimmed... */
+    int numBytes,	/* ...and its length in bytes */
+    const char *trim,	/* String of trim characters... */
+    int numTrim,	/* ...and its length in bytes */
+    int *trimRight)		/* Offset from the end of the string. */
+{
+    int trimLeft;
+    Tcl_DString bytesBuf, trimBuf;
+
+    *trimRight = 0;
+    /* Empty strings -> nothing to do */
+    if ((numBytes == 0) || (numTrim == 0)) {
+	return 0;
+    }
+
+    Tcl_DStringInit(&bytesBuf);
+    Tcl_DStringInit(&trimBuf);
+    bytes = UtfWellFormedEnd(&bytesBuf, bytes, numBytes);
+    trim = UtfWellFormedEnd(&trimBuf, trim, numTrim);
+
+    trimLeft = TrimLeft(bytes, numBytes, trim, numTrim);
+    if (trimLeft > numBytes) {
+	trimLeft = numBytes;
+    }
+    numBytes -= trimLeft;
+    /* have to trim yet (first char was already verified within TrimLeft) */
+    if (numBytes > 1) {
+	bytes += trimLeft;
+	*trimRight = TrimRight(bytes, numBytes, trim, numTrim);
+	if (*trimRight > numBytes) {
+	    *trimRight = numBytes;
+	}
+    }
+
+    Tcl_DStringFree(&bytesBuf);
+    Tcl_DStringFree(&trimBuf);
+
+    return trimLeft;
+}
 
 /*
  *----------------------------------------------------------------------
@@ -1869,30 +2000,20 @@ Tcl_Concat(
     result = ckalloc((unsigned) (bytesNeeded + argc));
 
     for (p = result, i = 0;  i < argc;  i++) {
-	int trim, elemLength;
+	int triml, trimr, elemLength;
 	const char *element;
 
 	element = argv[i];
 	elemLength = strlen(argv[i]);
 
-	/*
-	 * Trim away the leading whitespace.
-	 */
-
-	trim = TclTrimLeft(element, elemLength, CONCAT_TRIM_SET,
-		CONCAT_WS_SIZE);
-	element += trim;
-	elemLength -= trim;
-
-	/*
-	 * Trim away the trailing whitespace. Do not permit trimming to expose
-	 * a final backslash character.
-	 */
+	/* Trim away the leading/trailing whitespace. */
+	triml = TclTrim(element, elemLength, CONCAT_TRIM_SET,
+		CONCAT_WS_SIZE, &trimr);
+	element += triml;
+	elemLength -= triml + trimr;
 
-	trim = TclTrimRight(element, elemLength, CONCAT_TRIM_SET,
-		CONCAT_WS_SIZE);
-	trim -= trim && (element[elemLength - trim - 1] == '\\');
-	elemLength -= trim;
+	/* Do not permit trimming to expose a final backslash character. */
+	elemLength += trimr && (element[elemLength - 1] == '\\');
 
 	/*
 	 * If we're left with empty element after trimming, do nothing.
@@ -2012,28 +2133,18 @@ Tcl_ConcatObj(
     Tcl_SetObjLength(resPtr, 0);
 
     for (i = 0;  i < objc;  i++) {
-	int trim;
+	int triml, trimr;
 
 	element = TclGetStringFromObj(objv[i], &elemLength);
 
-	/*
-	 * Trim away the leading whitespace.
-	 */
-
-	trim = TclTrimLeft(element, elemLength, CONCAT_TRIM_SET,
-		CONCAT_WS_SIZE);
-	element += trim;
-	elemLength -= trim;
-
-	/*
-	 * Trim away the trailing whitespace. Do not permit trimming to expose
-	 * a final backslash character.
-	 */
+	/* Trim away the leading/trailing whitespace. */
+	triml = TclTrim(element, elemLength, CONCAT_TRIM_SET,
+		CONCAT_WS_SIZE, &trimr);
+	element += triml;
+	elemLength -= triml + trimr;
 
-	trim = TclTrimRight(element, elemLength, CONCAT_TRIM_SET,
-		CONCAT_WS_SIZE);
-	trim -= trim && (element[elemLength - trim - 1] == '\\');
-	elemLength -= trim;
+	/* Do not permit trimming to expose a final backslash character. */
+	elemLength += trimr && (element[elemLength - 1] == '\\');
 
 	/*
 	 * If we're left with empty element after trimming, do nothing.