3 files changed, 31 insertions, 14 deletions

diff --git a/lexlib/LexerBase.cxx b/lexlib/LexerBase.cxx
index f9e6292a1..ee3aa797e 100644
--- a/lexlib/LexerBase.cxx
+++ b/lexlib/LexerBase.cxx
@@ -75,10 +75,7 @@ const char * SCI_METHOD LexerBase::DescribeWordListSets() {
 
 Sci_Position SCI_METHOD LexerBase::WordListSet(int n, const char *wl) {
 	if (n < numWordLists) {
-		WordList wlNew;
-		wlNew.Set(wl);
-		if (*keyWordLists[n] != wlNew) {
-			keyWordLists[n]->Set(wl);
+		if (keyWordLists[n]->Set(wl)) {
 			return 0;
 		}
 	}
diff --git a/lexlib/WordList.cxx b/lexlib/WordList.cxx
index c8b4cd63b..937f18948 100644
--- a/lexlib/WordList.cxx
+++ b/lexlib/WordList.cxx
@@ -20,7 +20,7 @@ using namespace Scintilla;
  * Creates an array that points into each word in the string and puts \0 terminators
  * after each word.
  */
-static char **ArrayFromWordList(char *wordlist, int *len, bool onlyLineEnds = false) {
+static char **ArrayFromWordList(char *wordlist, size_t slen, int *len, bool onlyLineEnds = false) {
 	int prev = '\n';
 	int words = 0;
 	// For rapid determination of whether a character is a separator, build
@@ -40,7 +40,6 @@ static char **ArrayFromWordList(char *wordlist, int *len, bool onlyLineEnds = fa
 	}
 	char **keywords = new char *[words + 1];
 	int wordsStore = 0;
-	const size_t slen = strlen(wordlist);
 	if (words) {
 		prev = '\0';
 		for (size_t k = 0; k < slen; k++) {
@@ -117,22 +116,43 @@ static void SortWordList(char **words, unsigned int len) {
 
 #endif
 
-void WordList::Set(const char *s) {
-	Clear();
+bool WordList::Set(const char *s) {
 	const size_t lenS = strlen(s) + 1;
-	list = new char[lenS];
-	memcpy(list, s, lenS);
-	words = ArrayFromWordList(list, &len, onlyLineEnds);
+	char *listTemp = new char[lenS];
+	memcpy(listTemp, s, lenS);
+	int lenTemp = 0;
+	char **wordsTemp = ArrayFromWordList(listTemp, lenS - 1, &lenTemp, onlyLineEnds);
 #ifdef _MSC_VER
-	std::sort(words, words + len, cmpWords);
+	std::sort(wordsTemp, wordsTemp + lenTemp, cmpWords);
 #else
-	SortWordList(words, len);
+	SortWordList(wordsTemp, lenTemp);
 #endif
+
+	if (lenTemp == len) {
+		bool changed = false;
+		for (int i = 0; i < lenTemp; i++) {
+			if (strcmp(words[i], wordsTemp[i]) != 0) {
+				changed = true;
+				break;
+			}
+		}
+		if (!changed) {
+			delete []listTemp;
+			delete []wordsTemp;
+			return false;
+		}
+	}
+
+	Clear();
+	words = wordsTemp;
+	list = listTemp;
+	len = lenTemp;
 	std::fill(starts, std::end(starts), -1);
 	for (int l = len - 1; l >= 0; l--) {
 		unsigned char indexChar = words[l][0];
 		starts[indexChar] = l;
 	}
+	return true;
 }
 
 /** Check whether a string is in the list.
diff --git a/lexlib/WordList.h b/lexlib/WordList.h
index a9f2d4ab2..c1253cec6 100644
--- a/lexlib/WordList.h
+++ b/lexlib/WordList.h
@@ -26,7 +26,7 @@ public:
 	bool operator!=(const WordList &other) const;
 	int Length() const;
 	void Clear();
-	void Set(const char *s);
+	bool Set(const char *s);
 	bool InList(const char *s) const;
 	bool InListAbbreviated(const char *s, const char marker) const;
 	bool InListAbridged(const char *s, const char marker) const;