Index: source/i18n/regexcmp.h
===================================================================
--- source/i18n/regexcmp.h	(revision 292476)
+++ source/i18n/regexcmp.h	(working copy)
@@ -182,7 +182,9 @@
     int32_t                       fMatchOpenParen;   // The position in the compiled pattern
                                                      //   of the slot reserved for a state save
                                                      //   at the start of the most recently processed
-                                                     //   parenthesized block.
+                                                     //   parenthesized block. Updated when processing
+                                                     //   a close to the location for the corresponding open.
+
     int32_t                       fMatchCloseParen;  // The position in the pattern of the first
                                                      //   location after the most recently processed
                                                      //   parenthesized block.
Index: source/i18n/regexcmp.cpp
===================================================================
--- source/i18n/regexcmp.cpp	(revision 292476)
+++ source/i18n/regexcmp.cpp	(working copy)
@@ -2133,6 +2133,10 @@
             int32_t patEnd   = fRXPat->fCompiledPat->size() - 1;
             int32_t minML    = minMatchLength(fMatchOpenParen, patEnd);
             int32_t maxML    = maxMatchLength(fMatchOpenParen, patEnd);
+            if (URX_TYPE(maxML) != 0) {
+                error(U_REGEX_LOOK_BEHIND_LIMIT);
+                break;
+            }
             if (maxML == INT32_MAX) {
                 error(U_REGEX_LOOK_BEHIND_LIMIT);
                 break;
@@ -2166,6 +2170,10 @@
             int32_t patEnd   = fRXPat->fCompiledPat->size() - 1;
             int32_t minML    = minMatchLength(fMatchOpenParen, patEnd);
             int32_t maxML    = maxMatchLength(fMatchOpenParen, patEnd);
+            if (URX_TYPE(maxML) != 0) {
+                error(U_REGEX_LOOK_BEHIND_LIMIT);
+                break;
+            }
             if (maxML == INT32_MAX) {
                 error(U_REGEX_LOOK_BEHIND_LIMIT);
                 break;
@@ -2329,7 +2337,15 @@
     int32_t   topOfBlock = blockTopLoc(FALSE);
     if (fIntervalUpper == 0) {
         // Pathological case.  Attempt no matches, as if the block doesn't exist.
+        // Discard the generated code for the block.
+        // If the block included parens, discard the info pertaining to them as well.
         fRXPat->fCompiledPat->setSize(topOfBlock);
+        if (fMatchOpenParen >= topOfBlock) {
+            fMatchOpenParen = -1;
+        }
+        if (fMatchCloseParen >= topOfBlock) {
+            fMatchCloseParen = -1;
+        }
         return TRUE;
     }
 
Index: source/test/testdata/regextst.txt
===================================================================
--- source/test/testdata/regextst.txt	(revision 292476)
+++ source/test/testdata/regextst.txt	(working copy)
@@ -1173,6 +1173,24 @@
 "(?<=(?:){11})bc"                "<0>bc</0>"          # Empty (?:) expression.
 
 
+# Bug 11369
+#   Incorrect optimization of patterns with a zero length quantifier {0}
+
+"(.|b)(|b){0}\$(?#xxx){3}(?>\D*)"   "AAAAABBBBBCCCCCDDDDEEEEE"
+"(|b)ab(c)"                     "<0><1></1>ab<2>c</2></0>"
+"(|b){0}a{3}(D*)"               "<0>aaa<2></2></0>"
+"(|b){0,1}a{3}(D*)"             "<0><1></1>aaa<2></2></0>"
+"((|b){0})a{3}(D*)"             "<0><1></1>aaa<3></3></0>"
+
+# Bug 11370
+#   Max match length computation of look-behind expression gives result that is too big to fit in the
+#   in the 24 bit operand portion of the compiled code. Expressions should fail to compile
+#   (Look-behind match length must be bounded. This case is treated as unbounded, an error.)
+
+"(?<!(0123456789a){10000000})x"         E  "no match"
+"(?<!\\ubeaf(\\ubeaf{11000}){11000})"   E  "no match"
+
+
 #  Random debugging, Temporary
 #
 #"^(?:a?b?)*$"	                  "a--"