1 files changed, 19 insertions, 6 deletions

diff --git a/thirdparty/icu4c/common/unisetspan.cpp b/thirdparty/icu4c/common/unisetspan.cpp
index 68e44d91ee..fe0d74f5b2 100644
--- a/thirdparty/icu4c/common/unisetspan.cpp
+++ b/thirdparty/icu4c/common/unisetspan.cpp
@@ -231,6 +231,9 @@ UnicodeSetStringSpan::UnicodeSetStringSpan(const UnicodeSet &set,
         const UnicodeString &string=*(const UnicodeString *)strings.elementAt(i);
         const UChar *s16=string.getBuffer();
         int32_t length16=string.length();
+        if (length16==0) {
+            continue;  // skip the empty string
+        }
         UBool thisRelevant;
         spanLength=spanSet.span(s16, length16, USET_SPAN_CONTAINED);
         if(spanLength<length16) {  // Relevant string.
@@ -312,7 +315,7 @@ UnicodeSetStringSpan::UnicodeSetStringSpan(const UnicodeSet &set,
         const UChar *s16=string.getBuffer();
         int32_t length16=string.length();
         spanLength=spanSet.span(s16, length16, USET_SPAN_CONTAINED);
-        if(spanLength<length16) {  // Relevant string.
+        if(spanLength<length16 && length16>0) {  // Relevant string.
             if(which&UTF16) {
                 if(which&CONTAINED) {
                     if(which&FWD) {
@@ -362,7 +365,7 @@ UnicodeSetStringSpan::UnicodeSetStringSpan(const UnicodeSet &set,
                     addToSpanNotSet(c);
                 }
             }
-        } else {  // Irrelevant string.
+        } else {  // Irrelevant string. (Also the empty string.)
             if(which&UTF8) {
                 if(which&CONTAINED) {  // Only necessary for LONGEST_MATCH.
                     uint8_t *s8=utf8+utf8Count;
@@ -653,11 +656,12 @@ int32_t UnicodeSetStringSpan::span(const UChar *s, int32_t length, USetSpanCondi
             for(i=0; i<stringsLength; ++i) {
                 int32_t overlap=spanLengths[i];
                 if(overlap==ALL_CP_CONTAINED) {
-                    continue;  // Irrelevant string.
+                    continue;  // Irrelevant string. (Also the empty string.)
                 }
                 const UnicodeString &string=*(const UnicodeString *)strings.elementAt(i);
                 const UChar *s16=string.getBuffer();
                 int32_t length16=string.length();
+                U_ASSERT(length>0);
 
                 // Try to match this string at pos-overlap..pos.
                 if(overlap>=LONG_SPAN) {
@@ -697,6 +701,9 @@ int32_t UnicodeSetStringSpan::span(const UChar *s, int32_t length, USetSpanCondi
                 const UnicodeString &string=*(const UnicodeString *)strings.elementAt(i);
                 const UChar *s16=string.getBuffer();
                 int32_t length16=string.length();
+                if (length16==0) {
+                    continue;  // skip the empty string
+                }
 
                 // Try to match this string at pos-overlap..pos.
                 if(overlap>=LONG_SPAN) {
@@ -817,11 +824,12 @@ int32_t UnicodeSetStringSpan::spanBack(const UChar *s, int32_t length, USetSpanC
             for(i=0; i<stringsLength; ++i) {
                 int32_t overlap=spanBackLengths[i];
                 if(overlap==ALL_CP_CONTAINED) {
-                    continue;  // Irrelevant string.
+                    continue;  // Irrelevant string. (Also the empty string.)
                 }
                 const UnicodeString &string=*(const UnicodeString *)strings.elementAt(i);
                 const UChar *s16=string.getBuffer();
                 int32_t length16=string.length();
+                U_ASSERT(length>0);
 
                 // Try to match this string at pos-(length16-overlap)..pos-length16.
                 if(overlap>=LONG_SPAN) {
@@ -863,6 +871,9 @@ int32_t UnicodeSetStringSpan::spanBack(const UChar *s, int32_t length, USetSpanC
                 const UnicodeString &string=*(const UnicodeString *)strings.elementAt(i);
                 const UChar *s16=string.getBuffer();
                 int32_t length16=string.length();
+                if (length16==0) {
+                    continue;  // skip the empty string
+                }
 
                 // Try to match this string at pos-(length16-overlap)..pos-length16.
                 if(overlap>=LONG_SPAN) {
@@ -1358,11 +1369,12 @@ int32_t UnicodeSetStringSpan::spanNot(const UChar *s, int32_t length) const {
         // Try to match the strings at pos.
         for(i=0; i<stringsLength; ++i) {
             if(spanLengths[i]==ALL_CP_CONTAINED) {
-                continue;  // Irrelevant string.
+                continue;  // Irrelevant string. (Also the empty string.)
             }
             const UnicodeString &string=*(const UnicodeString *)strings.elementAt(i);
             const UChar *s16=string.getBuffer();
             int32_t length16=string.length();
+            U_ASSERT(length>0);
             if(length16<=rest && matches16CPB(s, pos, length, s16, length16)) {
                 return pos;  // There is a set element at pos.
             }
@@ -1401,11 +1413,12 @@ int32_t UnicodeSetStringSpan::spanNotBack(const UChar *s, int32_t length) const
             // it is easier and we only need to know whether the string is irrelevant
             // which is the same in either array.
             if(spanLengths[i]==ALL_CP_CONTAINED) {
-                continue;  // Irrelevant string.
+                continue;  // Irrelevant string. (Also the empty string.)
             }
             const UnicodeString &string=*(const UnicodeString *)strings.elementAt(i);
             const UChar *s16=string.getBuffer();
             int32_t length16=string.length();
+            U_ASSERT(length>0);
             if(length16<=pos && matches16CPB(s, pos-length16, length, s16, length16)) {
                 return pos;  // There is a set element at pos.
             }