Index: source/common/unicode/utypes.h
===================================================================
--- source/common/unicode/utypes.h	(revision 292709)
+++ source/common/unicode/utypes.h	(working copy)
@@ -647,6 +647,7 @@
     U_REGEX_STACK_OVERFLOW,               /**< Regular expression backtrack stack overflow.       */
     U_REGEX_TIME_OUT,                     /**< Maximum allowed match time exceeded                */
     U_REGEX_STOPPED_BY_CALLER,            /**< Matching operation aborted by user callback fn.    */
+    U_REGEX_PATTERN_TOO_BIG,              /**< Pattern exceeds limits on size or complexity.      */
     U_REGEX_ERROR_LIMIT,                  /**< This must always be the last value to indicate the limit for regexp errors */
 
     /*
Index: source/common/utypes.c
===================================================================
--- source/common/utypes.c	(revision 292709)
+++ source/common/utypes.c	(working copy)
@@ -165,7 +165,8 @@
     "U_REGEX_INVALID_RANGE",
     "U_REGEX_STACK_OVERFLOW",
     "U_REGEX_TIME_OUT",
-    "U_REGEX_STOPPED_BY_CALLER"
+    "U_REGEX_STOPPED_BY_CALLER",
+    "U_REGEX_PATTERN_TOO_BIG"
 };
 
 static const char * const
Index: source/i18n/regexcmp.cpp
===================================================================
--- source/i18n/regexcmp.cpp	(revision 292943)
+++ source/i18n/regexcmp.cpp	(working copy)
@@ -302,7 +302,7 @@
     //   present in the saved state:  the input string position (int64_t) and
     //   the position in the compiled pattern.
     //
-    fRXPat->fFrameSize+=RESTACKFRAME_HDRCOUNT;
+    allocateStackData(RESTACKFRAME_HDRCOUNT);
 
     //
     // Optimization pass 1: NOPs, back-references, and case-folding
@@ -368,9 +368,9 @@
         //                    the start of an ( grouping.
         //4   NOP             Resreved, will be replaced by a save if there are
         //                    OR | operators at the top level
-        fRXPat->fCompiledPat->addElement(URX_BUILD(URX_STATE_SAVE, 2), *fStatus);
-        fRXPat->fCompiledPat->addElement(URX_BUILD(URX_JMP,  3), *fStatus);
-        fRXPat->fCompiledPat->addElement(URX_BUILD(URX_FAIL, 0), *fStatus);
+        appendOp(URX_BUILD(URX_STATE_SAVE, 2));
+        appendOp(URX_BUILD(URX_JMP,  3));
+        appendOp(URX_BUILD(URX_FAIL, 0));
 
         // Standard open nonCapture paren action emits the two NOPs and
         //   sets up the paren stack frame.
@@ -393,7 +393,7 @@
         }
 
         // add the END operation to the compiled pattern.
-        fRXPat->fCompiledPat->addElement(URX_BUILD(URX_END, 0), *fStatus);
+        appendOp(URX_BUILD(URX_END, 0));
 
         // Terminate the pattern compilation state machine.
         returnVal = FALSE;
@@ -422,7 +422,7 @@
             //  the JMP will eventually be the location following the ')' for the
             //  group.  This will be patched in later, when the ')' is encountered.
             op = URX_BUILD(URX_JMP, 0);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
 
             // Push the position of the newly added JMP op onto the parentheses stack.
             // This registers if for fixup when this block's close paren is encountered.
@@ -431,7 +431,7 @@
             // Append a NOP to the compiled pattern.  This is the slot reserved
             //   for a SAVE in the event that there is yet another '|' following
             //   this one.
-            fRXPat->fCompiledPat->addElement(URX_BUILD(URX_NOP, 0), *fStatus);
+            appendOp(URX_BUILD(URX_NOP, 0));
             fParenStack.push(fRXPat->fCompiledPat->size()-1, *fStatus);
         }
         break;
@@ -457,12 +457,11 @@
         //      END_CAPTURE is encountered.
         {
             fixLiterals();
-            fRXPat->fCompiledPat->addElement(URX_BUILD(URX_NOP, 0), *fStatus);
-            int32_t  varsLoc    = fRXPat->fFrameSize;    // Reserve three slots in match stack frame.
-            fRXPat->fFrameSize += 3;
-            int32_t  cop        = URX_BUILD(URX_START_CAPTURE, varsLoc);
-            fRXPat->fCompiledPat->addElement(cop, *fStatus);
-            fRXPat->fCompiledPat->addElement(URX_BUILD(URX_NOP, 0), *fStatus);
+            appendOp(URX_BUILD(URX_NOP, 0));
+            int32_t  varsLoc = allocateStackData(3);    // Reserve three slots in match stack frame.
+            int32_t  cop     = URX_BUILD(URX_START_CAPTURE, varsLoc);
+            appendOp(cop);
+            appendOp(URX_BUILD(URX_NOP, 0));
 
             // On the Parentheses stack, start a new frame and add the postions
             //   of the two NOPs.  Depending on what follows in the pattern, the
@@ -487,8 +486,8 @@
         //             is an '|' alternation within the parens.
         {
             fixLiterals();
-            fRXPat->fCompiledPat->addElement(URX_BUILD(URX_NOP, 0), *fStatus);
-            fRXPat->fCompiledPat->addElement(URX_BUILD(URX_NOP, 0), *fStatus);
+            appendOp(URX_BUILD(URX_NOP, 0));
+            appendOp(URX_BUILD(URX_NOP, 0));
 
             // On the Parentheses stack, start a new frame and add the postions
             //   of the two NOPs.
@@ -510,12 +509,11 @@
         //             is an '|' alternation within the parens.
         {
             fixLiterals();
-            fRXPat->fCompiledPat->addElement(URX_BUILD(URX_NOP, 0), *fStatus);
-            int32_t  varLoc    = fRXPat->fDataSize;    // Reserve a data location for saving the
-            fRXPat->fDataSize += 1;                    //  state stack ptr.
-            int32_t  stoOp     = URX_BUILD(URX_STO_SP, varLoc);
-            fRXPat->fCompiledPat->addElement(stoOp, *fStatus);
-            fRXPat->fCompiledPat->addElement(URX_BUILD(URX_NOP, 0), *fStatus);
+            appendOp(URX_BUILD(URX_NOP, 0));
+            int32_t  varLoc = allocateData(1);    // Reserve a data location for saving the state stack ptr.
+            int32_t  stoOp = URX_BUILD(URX_STO_SP, varLoc);
+            appendOp(stoOp);
+            appendOp(URX_BUILD(URX_NOP, 0));
 
             // On the Parentheses stack, start a new frame and add the postions
             //   of the two NOPs.  Depending on what follows in the pattern, the
@@ -558,26 +556,25 @@
         //  Two data slots are reserved, for saving the stack ptr and the input position.
         {
             fixLiterals();
-            int32_t dataLoc = fRXPat->fDataSize;
-            fRXPat->fDataSize += 2;
+            int32_t dataLoc = allocateData(2);
             int32_t op = URX_BUILD(URX_LA_START, dataLoc);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
 
             op = URX_BUILD(URX_STATE_SAVE, fRXPat->fCompiledPat->size()+ 2);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
 
             op = URX_BUILD(URX_JMP, fRXPat->fCompiledPat->size()+ 3);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
-            
+            appendOp(op);
+
             op = URX_BUILD(URX_LA_END, dataLoc);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
 
             op = URX_BUILD(URX_BACKTRACK, 0);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
-            
+            appendOp(op);
+
             op = URX_BUILD(URX_NOP, 0);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
+            appendOp(op);
 
             // On the Parentheses stack, start a new frame and add the postions
             //   of the NOPs.
@@ -602,16 +599,15 @@
         //                                        an alternate (transparent) region.
         {
             fixLiterals();
-            int32_t dataLoc = fRXPat->fDataSize;
-            fRXPat->fDataSize += 2;
+            int32_t dataLoc = allocateData(2);
             int32_t op = URX_BUILD(URX_LA_START, dataLoc);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
 
             op = URX_BUILD(URX_STATE_SAVE, 0);    // dest address will be patched later.
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
 
             op = URX_BUILD(URX_NOP, 0);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
 
             // On the Parentheses stack, start a new frame and add the postions
             //   of the StateSave and NOP.
@@ -649,23 +645,22 @@
             fixLiterals();
 
             // Allocate data space
-            int32_t dataLoc = fRXPat->fDataSize;
-            fRXPat->fDataSize += 4;
+            int32_t dataLoc = allocateData(4);
 
             // Emit URX_LB_START
             int32_t op = URX_BUILD(URX_LB_START, dataLoc);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
 
             // Emit URX_LB_CONT
             op = URX_BUILD(URX_LB_CONT, dataLoc);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
-            fRXPat->fCompiledPat->addElement(0,  *fStatus);    // MinMatchLength.  To be filled later.
-            fRXPat->fCompiledPat->addElement(0,  *fStatus);    // MaxMatchLength.  To be filled later.
+            appendOp(op);
+            appendOp(0);    // MinMatchLength.  To be filled later.
+            appendOp(0);    // MaxMatchLength.  To be filled later.
 
             // Emit the NOP
             op = URX_BUILD(URX_NOP, 0);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
+            appendOp(op);
 
             // On the Parentheses stack, start a new frame and add the postions
             //   of the URX_LB_CONT and the NOP.
@@ -705,24 +700,23 @@
             fixLiterals();
 
             // Allocate data space
-            int32_t dataLoc = fRXPat->fDataSize;
-            fRXPat->fDataSize += 4;
+            int32_t dataLoc = allocateData(4);
 
             // Emit URX_LB_START
             int32_t op = URX_BUILD(URX_LB_START, dataLoc);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
 
             // Emit URX_LBN_CONT
             op = URX_BUILD(URX_LBN_CONT, dataLoc);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
-            fRXPat->fCompiledPat->addElement(0,  *fStatus);    // MinMatchLength.  To be filled later.
-            fRXPat->fCompiledPat->addElement(0,  *fStatus);    // MaxMatchLength.  To be filled later.
-            fRXPat->fCompiledPat->addElement(0,  *fStatus);    // Continue Loc.    To be filled later.
+            appendOp(op);
+            appendOp(0);    // MinMatchLength.  To be filled later.
+            appendOp(0);    // MaxMatchLength.  To be filled later.
+            appendOp(0);    // Continue Loc.    To be filled later.
 
             // Emit the NOP
             op = URX_BUILD(URX_NOP, 0);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
+            appendOp(op);
 
             // On the Parentheses stack, start a new frame and add the postions
             //   of the URX_LB_CONT and the NOP.
@@ -793,11 +787,10 @@
                 if (URX_TYPE(repeatedOp) == URX_SETREF) {
                     // Emit optimized code for [char set]+
                     int32_t loopOpI = URX_BUILD(URX_LOOP_SR_I, URX_VAL(repeatedOp));
-                    fRXPat->fCompiledPat->addElement(loopOpI, *fStatus);
-                    frameLoc = fRXPat->fFrameSize;
-                    fRXPat->fFrameSize++;
+                    appendOp(loopOpI);
+                    frameLoc = allocateStackData(1);
                     int32_t loopOpC = URX_BUILD(URX_LOOP_C, frameLoc);
-                    fRXPat->fCompiledPat->addElement(loopOpC, *fStatus);
+                    appendOp(loopOpC);
                     break;
                 }
 
@@ -813,11 +806,10 @@
                     if (fModeFlags & UREGEX_UNIX_LINES) {
                         loopOpI |= 2;
                     }
-                    fRXPat->fCompiledPat->addElement(loopOpI, *fStatus);
-                    frameLoc = fRXPat->fFrameSize;
-                    fRXPat->fFrameSize++;
+                    appendOp(loopOpI);
+                    frameLoc = allocateStackData(1);
                     int32_t loopOpC = URX_BUILD(URX_LOOP_C, frameLoc);
-                    fRXPat->fCompiledPat->addElement(loopOpC, *fStatus);
+                    appendOp(loopOpC);
                     break;
                 }
 
@@ -831,18 +823,17 @@
                 // Zero length match is possible.
                 // Emit the code sequence that can handle it.
                 insertOp(topLoc);
-                frameLoc =  fRXPat->fFrameSize;
-                fRXPat->fFrameSize++;
+                frameLoc = allocateStackData(1);
 
                 int32_t op = URX_BUILD(URX_STO_INP_LOC, frameLoc);
                 fRXPat->fCompiledPat->setElementAt(op, topLoc);
 
                 op = URX_BUILD(URX_JMP_SAV_X, topLoc+1);
-                fRXPat->fCompiledPat->addElement(op, *fStatus);
+                appendOp(op);
             } else {
                 // Simpler code when the repeated body must match something non-empty
                 int32_t  jmpOp  = URX_BUILD(URX_JMP_SAV, topLoc);
-                fRXPat->fCompiledPat->addElement(jmpOp, *fStatus);
+                appendOp(jmpOp);
             }
         }
         break;
@@ -855,7 +846,7 @@
         {
             int32_t topLoc      = blockTopLoc(FALSE);
             int32_t saveStateOp = URX_BUILD(URX_STATE_SAVE, topLoc);
-            fRXPat->fCompiledPat->addElement(saveStateOp, *fStatus);
+            appendOp(saveStateOp);
         }
         break;
 
@@ -892,10 +883,10 @@
             fRXPat->fCompiledPat->setElementAt(jmp1_op, jmp1_loc);
 
             int32_t  jmp2_op  = URX_BUILD(URX_JMP, jmp2_loc+2);
-            fRXPat->fCompiledPat->addElement(jmp2_op, *fStatus);
+            appendOp(jmp2_op);
 
             int32_t  save_op  = URX_BUILD(URX_STATE_SAVE, jmp1_loc+1);
-            fRXPat->fCompiledPat->addElement(save_op, *fStatus);
+            appendOp(save_op);
         }
         break;
 
@@ -937,10 +928,9 @@
                     // Emit optimized code for a [char set]*
                     int32_t loopOpI = URX_BUILD(URX_LOOP_SR_I, URX_VAL(repeatedOp));
                     fRXPat->fCompiledPat->setElementAt(loopOpI, topLoc);
-                    dataLoc = fRXPat->fFrameSize;
-                    fRXPat->fFrameSize++;
+                    dataLoc = allocateStackData(1);
                     int32_t loopOpC = URX_BUILD(URX_LOOP_C, dataLoc);
-                    fRXPat->fCompiledPat->addElement(loopOpC, *fStatus);
+                    appendOp(loopOpC);
                     break;
                 }
 
@@ -957,10 +947,9 @@
                         loopOpI |= 2;
                     }
                     fRXPat->fCompiledPat->setElementAt(loopOpI, topLoc);
-                    dataLoc = fRXPat->fFrameSize;
-                    fRXPat->fFrameSize++;
+                    dataLoc = allocateStackData(1);
                     int32_t loopOpC = URX_BUILD(URX_LOOP_C, dataLoc);
-                    fRXPat->fCompiledPat->addElement(loopOpC, *fStatus);
+                    appendOp(loopOpC);
                     break;
                 }
             }
@@ -975,8 +964,7 @@
             //    extra loop-breaking code.
             if (minMatchLength(saveStateLoc, fRXPat->fCompiledPat->size()-1) == 0) {
                 insertOp(saveStateLoc);
-                dataLoc =  fRXPat->fFrameSize;
-                fRXPat->fFrameSize++;
+                dataLoc = allocateStackData(1);
 
                 int32_t op = URX_BUILD(URX_STO_INP_LOC, dataLoc);
                 fRXPat->fCompiledPat->setElementAt(op, saveStateLoc+1);
@@ -992,7 +980,7 @@
             fRXPat->fCompiledPat->setElementAt(saveStateOp, saveStateLoc);
 
             // Append the URX_JMP_SAV or URX_JMPX operation to the compiled pattern.
-            fRXPat->fCompiledPat->addElement(jmpOp, *fStatus);
+            appendOp(jmpOp);
         }
         break;
 
@@ -1009,7 +997,7 @@
             int32_t     jmpOp   = URX_BUILD(URX_JMP, saveLoc);
             int32_t     stateSaveOp = URX_BUILD(URX_STATE_SAVE, jmpLoc+1);
             fRXPat->fCompiledPat->setElementAt(jmpOp, jmpLoc);
-            fRXPat->fCompiledPat->addElement(stateSaveOp, *fStatus);
+            appendOp(stateSaveOp);
         }
         break;
 
@@ -1078,9 +1066,9 @@
 
             // First the STO_SP before the start of the loop
             insertOp(topLoc);
-            int32_t  varLoc    = fRXPat->fDataSize;    // Reserve a data location for saving the
-            fRXPat->fDataSize += 1;                    //  state stack ptr.
-            int32_t  op        = URX_BUILD(URX_STO_SP, varLoc);
+
+            int32_t  varLoc = allocateData(1);   // Reserve a data location for saving the
+            int32_t  op     = URX_BUILD(URX_STO_SP, varLoc);
             fRXPat->fCompiledPat->setElementAt(op, topLoc);
 
             int32_t loopOp = (int32_t)fRXPat->fCompiledPat->popi();
@@ -1090,7 +1078,7 @@
 
             // Then the LD_SP after the end of the loop
             op = URX_BUILD(URX_LD_SP, varLoc);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
         }
 
         break;
@@ -1134,7 +1122,7 @@
             } else {
                 op = URX_BUILD(URX_DOTANY, 0);
             }
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
         }
         break;
 
@@ -1151,7 +1139,7 @@
             } else if ((fModeFlags & UREGEX_MULTILINE) != 0 && (fModeFlags & UREGEX_UNIX_LINES) != 0) {
                 op = URX_CARET_M_UNIX;
             }
-            fRXPat->fCompiledPat->addElement(URX_BUILD(op, 0), *fStatus);
+            appendOp(URX_BUILD(op, 0));
         }
         break;
 
@@ -1168,13 +1156,13 @@
             } else if ((fModeFlags & UREGEX_MULTILINE) != 0 && (fModeFlags & UREGEX_UNIX_LINES) != 0) {
                 op = URX_DOLLAR_MD;
             }
-            fRXPat->fCompiledPat->addElement(URX_BUILD(op, 0), *fStatus);
+            appendOp(URX_BUILD(op, 0));
         }
         break;
 
     case doBackslashA:
         fixLiterals(FALSE);
-        fRXPat->fCompiledPat->addElement(URX_BUILD(URX_CARET, 0), *fStatus);
+        appendOp(URX_BUILD(URX_CARET, 0));
         break;
 
     case doBackslashB:
@@ -1186,7 +1174,7 @@
             #endif
             fixLiterals(FALSE);
             int32_t op = (fModeFlags & UREGEX_UWORD)? URX_BACKSLASH_BU : URX_BACKSLASH_B;
-            fRXPat->fCompiledPat->addElement(URX_BUILD(op, 1), *fStatus);
+            appendOp(URX_BUILD(op, 1));
         }
         break;
 
@@ -1199,63 +1187,59 @@
             #endif
             fixLiterals(FALSE);
             int32_t op = (fModeFlags & UREGEX_UWORD)? URX_BACKSLASH_BU : URX_BACKSLASH_B;
-            fRXPat->fCompiledPat->addElement(URX_BUILD(op, 0), *fStatus);
+            appendOp(URX_BUILD(op, 0));
         }
         break;
 
     case doBackslashD:
         fixLiterals(FALSE);
-        fRXPat->fCompiledPat->addElement(URX_BUILD(URX_BACKSLASH_D, 1), *fStatus);
+        appendOp(URX_BUILD(URX_BACKSLASH_D, 1));
         break;
 
     case doBackslashd:
         fixLiterals(FALSE);
-        fRXPat->fCompiledPat->addElement(URX_BUILD(URX_BACKSLASH_D, 0), *fStatus);
+        appendOp(URX_BUILD(URX_BACKSLASH_D, 0));
         break;
 
     case doBackslashG:
         fixLiterals(FALSE);
-        fRXPat->fCompiledPat->addElement(URX_BUILD(URX_BACKSLASH_G, 0), *fStatus);
+        appendOp(URX_BUILD(URX_BACKSLASH_G, 0));
         break;
 
     case doBackslashS:
         fixLiterals(FALSE);
-        fRXPat->fCompiledPat->addElement(
-            URX_BUILD(URX_STAT_SETREF_N, URX_ISSPACE_SET), *fStatus);
+        appendOp(URX_BUILD(URX_STAT_SETREF_N, URX_ISSPACE_SET));
         break;
 
     case doBackslashs:
         fixLiterals(FALSE);
-        fRXPat->fCompiledPat->addElement(
-            URX_BUILD(URX_STATIC_SETREF, URX_ISSPACE_SET), *fStatus);
+        appendOp(URX_BUILD(URX_STATIC_SETREF, URX_ISSPACE_SET));
         break;
 
     case doBackslashW:
         fixLiterals(FALSE);
-        fRXPat->fCompiledPat->addElement(
-            URX_BUILD(URX_STAT_SETREF_N, URX_ISWORD_SET), *fStatus);
+        appendOp(URX_BUILD(URX_STAT_SETREF_N, URX_ISWORD_SET));
         break;
 
     case doBackslashw:
         fixLiterals(FALSE);
-        fRXPat->fCompiledPat->addElement(
-            URX_BUILD(URX_STATIC_SETREF, URX_ISWORD_SET), *fStatus);
+        appendOp(URX_BUILD(URX_STATIC_SETREF, URX_ISWORD_SET));
         break;
 
     case doBackslashX:
         fixLiterals(FALSE);
-        fRXPat->fCompiledPat->addElement(URX_BUILD(URX_BACKSLASH_X, 0), *fStatus);
+        appendOp(URX_BUILD(URX_BACKSLASH_X, 0));
         break;
 
 
     case doBackslashZ:
         fixLiterals(FALSE);
-        fRXPat->fCompiledPat->addElement(URX_BUILD(URX_DOLLAR, 0), *fStatus);
+        appendOp(URX_BUILD(URX_DOLLAR, 0));
         break;
 
     case doBackslashz:
         fixLiterals(FALSE);
-        fRXPat->fCompiledPat->addElement(URX_BUILD(URX_BACKSLASH_Z, 0), *fStatus);
+        appendOp(URX_BUILD(URX_BACKSLASH_Z, 0));
         break;
 
     case doEscapeError:
@@ -1321,7 +1305,7 @@
             } else {
                 op = URX_BUILD(URX_BACKREF, groupNum);
             }
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
         }
         break;
 
@@ -1342,22 +1326,21 @@
         {
             // Emit the STO_SP
             int32_t   topLoc = blockTopLoc(TRUE);
-            int32_t   stoLoc = fRXPat->fDataSize;
-            fRXPat->fDataSize++;       // Reserve the data location for storing save stack ptr.
+            int32_t   stoLoc = allocateData(1);  // Reserve the data location for storing save stack ptr.
             int32_t   op     = URX_BUILD(URX_STO_SP, stoLoc);
             fRXPat->fCompiledPat->setElementAt(op, topLoc);
 
             // Emit the STATE_SAVE
             op = URX_BUILD(URX_STATE_SAVE, fRXPat->fCompiledPat->size()+2);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
 
             // Emit the JMP
             op = URX_BUILD(URX_JMP, topLoc+1);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
 
             // Emit the LD_SP
             op = URX_BUILD(URX_LD_SP, stoLoc);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
         }
         break;
 
@@ -1377,8 +1360,7 @@
             insertOp(topLoc);
 
             // emit   STO_SP     loc
-            int32_t   stoLoc = fRXPat->fDataSize;
-            fRXPat->fDataSize++;       // Reserve the data location for storing save stack ptr.
+            int32_t   stoLoc = allocateData(1);    // Reserve the data location for storing save stack ptr.
             int32_t   op     = URX_BUILD(URX_STO_SP, stoLoc);
             fRXPat->fCompiledPat->setElementAt(op, topLoc);
 
@@ -1389,11 +1371,11 @@
 
             // Append the JMP operation.
             op = URX_BUILD(URX_JMP, topLoc+1);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
 
             // Emit the LD_SP       loc
             op = URX_BUILD(URX_LD_SP, stoLoc);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
         }
         break;
 
@@ -1412,8 +1394,7 @@
             insertOp(topLoc);
 
             // Emit the STO_SP
-            int32_t   stoLoc = fRXPat->fDataSize;
-            fRXPat->fDataSize++;       // Reserve the data location for storing save stack ptr.
+            int32_t   stoLoc = allocateData(1);   // Reserve the data location for storing save stack ptr.
             int32_t   op     = URX_BUILD(URX_STO_SP, stoLoc);
             fRXPat->fCompiledPat->setElementAt(op, topLoc);
 
@@ -1424,7 +1405,7 @@
 
             // Emit the LD_SP
             op = URX_BUILD(URX_LD_SP, stoLoc);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
         }
         break;
 
@@ -1481,8 +1462,8 @@
         //             is an '|' alternation within the parens.
         {
             fixLiterals(FALSE);
-            fRXPat->fCompiledPat->addElement(URX_BUILD(URX_NOP, 0), *fStatus);
-            fRXPat->fCompiledPat->addElement(URX_BUILD(URX_NOP, 0), *fStatus);
+            appendOp(URX_BUILD(URX_NOP, 0));
+            appendOp(URX_BUILD(URX_NOP, 0));
 
             // On the Parentheses stack, start a new frame and add the postions
             //   of the two NOPs (a normal non-capturing () frame, except for the
@@ -1862,7 +1843,7 @@
         } else {
             op = URX_BUILD(URX_ONECHAR, lastCodePoint);
         }
-        fRXPat->fCompiledPat->addElement(op, *fStatus);
+        appendOp(op);
     } else {
         // Two or more chars, emit a URX_STRING to match them.
         if (fModeFlags & UREGEX_CASE_INSENSITIVE) {
@@ -1872,12 +1853,19 @@
             //             into two single char ops, for efficiency.
             op = URX_BUILD(URX_STRING, fRXPat->fLiteralText.length());
         }
-        fRXPat->fCompiledPat->addElement(op, *fStatus);
+        appendOp(op);
         op = URX_BUILD(URX_STRING_LEN, fLiteralChars.length());
-        fRXPat->fCompiledPat->addElement(op, *fStatus);
-        
+        appendOp(op);
+
         // Add this string into the accumulated strings of the compiled pattern.
+        // The total size of the accumulated strings must be restricted to 24 bits because
+        // string indexes appear as compiled pattern operand values.
+        // This is the only place that the pattern.fLiteralText string is modified.
+
         fRXPat->fLiteralText.append(fLiteralChars);
+        if (U_SUCCESS(*fStatus) && fRXPat->fLiteralText.length() > 0x00ffffff) {
+            *fStatus = U_REGEX_PATTERN_TOO_BIG;
+        }
     }
 
     fLiteralChars.remove();
@@ -1884,10 +1872,22 @@
 }
 
 
+//------------------------------------------------------------------------------
+//
+//   appendOp()             Append a new instruction onto the compiled pattern
+//                          Includes error checking, limiting the size of the
+//                          pattern to lengths that can be represented in the
+//                          24 bit operand field of an instruction.
+//
+//------------------------------------------------------------------------------
+void RegexCompile::appendOp(int32_t op) {
+    fRXPat->fCompiledPat->addElement(op, *fStatus);
+    if ((fRXPat->fCompiledPat->size() > 0x00fffff0) && U_SUCCESS(*fStatus)) {
+        *fStatus = U_REGEX_PATTERN_TOO_BIG;
+    }
+}
 
 
-
-
 //------------------------------------------------------------------------------
 //
 //   insertOp()             Insert a slot for a new opcode into the already
@@ -1947,9 +1947,61 @@
 }
 
 
+//------------------------------------------------------------------------------
+//
+//   allocateData()        Allocate storage in the matcher's static data area.
+//                         Return the index for the newly allocated data.
+//                         The storage won't actually exist until we are running a match
+//                         operation, but the storage indexes are inserted into various
+//                         opcodes while compiling the pattern.
+//
+//------------------------------------------------------------------------------
+int32_t RegexCompile::allocateData(int32_t size) {
+    if (U_FAILURE(*fStatus)) {
+        return 0;
+    }
+    if (size <= 0 || size > 0x100 || fRXPat->fDataSize < 0) {
+        *fStatus = U_REGEX_INTERNAL_ERROR;
+        return 0;
+    }
+    int32_t dataIndex = fRXPat->fDataSize;
+    fRXPat->fDataSize += size;
+    if (fRXPat->fDataSize >= 0x00fffff0) {
+        *fStatus = U_REGEX_PATTERN_TOO_BIG;
+    }
+    return dataIndex;
+}
 
+
 //------------------------------------------------------------------------------
 //
+//   allocateStackData()   Allocate space in the back-tracking stack frame.
+//                         Return the index for the newly allocated data.
+//                         The frame indexes are inserted into various
+//                         opcodes while compiling the pattern, meaning that frame
+//                         size must be restricted to the size that will fit
+//                         as an operand (24 bits).
+//
+//------------------------------------------------------------------------------
+int32_t RegexCompile::allocateStackData(int32_t size) {
+    if (U_FAILURE(*fStatus)) {
+        return 0;
+    }
+    if (size <= 0 || size > 0x100 || fRXPat->fFrameSize < 0) {
+        *fStatus = U_REGEX_INTERNAL_ERROR;
+        return 0;
+    }
+    int32_t dataIndex = fRXPat->fFrameSize;
+    fRXPat->fFrameSize += size;
+    if (fRXPat->fFrameSize >= 0x00fffff0) {
+        *fStatus = U_REGEX_PATTERN_TOO_BIG;
+    }
+    return dataIndex;
+}
+
+
+//------------------------------------------------------------------------------
+//
 //   blockTopLoc()          Find or create a location in the compiled pattern
 //                          at the start of the operation or block that has
 //                          just been compiled.  Needed when a quantifier (* or
@@ -2065,7 +2117,7 @@
 
             int32_t   frameVarLocation = URX_VAL(captureOp);
             int32_t   endCaptureOp = URX_BUILD(URX_END_CAPTURE, frameVarLocation);
-            fRXPat->fCompiledPat->addElement(endCaptureOp, *fStatus);
+            appendOp(endCaptureOp);
         }
         break;
     case atomic:
@@ -2077,7 +2129,7 @@
             U_ASSERT(URX_TYPE(stoOp) == URX_STO_SP);
             int32_t   stoLoc = URX_VAL(stoOp);
             int32_t   ldOp   = URX_BUILD(URX_LD_SP, stoLoc);
-            fRXPat->fCompiledPat->addElement(ldOp, *fStatus);
+            appendOp(ldOp);
         }
         break;
 
@@ -2087,7 +2139,7 @@
             U_ASSERT(URX_TYPE(startOp) == URX_LA_START);
             int32_t dataLoc  = URX_VAL(startOp);
             int32_t op       = URX_BUILD(URX_LA_END, dataLoc);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
         }
         break;
 
@@ -2098,11 +2150,11 @@
             U_ASSERT(URX_TYPE(startOp) == URX_LA_START);
             int32_t dataLoc  = URX_VAL(startOp);
             int32_t op       = URX_BUILD(URX_LA_END, dataLoc);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
             op               = URX_BUILD(URX_BACKTRACK, 0);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
             op               = URX_BUILD(URX_LA_END, dataLoc);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
 
             // Patch the URX_SAVE near the top of the block.
             // The destination of the SAVE is the final LA_END that was just added.
@@ -2123,9 +2175,9 @@
             U_ASSERT(URX_TYPE(startOp) == URX_LB_START);
             int32_t dataLoc  = URX_VAL(startOp);
             int32_t op       = URX_BUILD(URX_LB_END, dataLoc);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
-                    op       = URX_BUILD(URX_LA_END, dataLoc);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
+            op = URX_BUILD(URX_LA_END, dataLoc);
+            appendOp(op);
 
             // Determine the min and max bounds for the length of the
             //  string that the pattern can match.
@@ -2162,7 +2214,7 @@
             U_ASSERT(URX_TYPE(startOp) == URX_LB_START);
             int32_t dataLoc  = URX_VAL(startOp);
             int32_t op       = URX_BUILD(URX_LBN_END, dataLoc);
-            fRXPat->fCompiledPat->addElement(op, *fStatus);
+            appendOp(op);
 
             // Determine the min and max bounds for the length of the
             //  string that the pattern can match.
@@ -2228,7 +2280,7 @@
     case 0:
         {
             // Set of no elements.   Always fails to match.
-            fRXPat->fCompiledPat->addElement(URX_BUILD(URX_BACKTRACK, 0), *fStatus);
+            appendOp(URX_BUILD(URX_BACKTRACK, 0));
             delete theSet;
         }
         break;
@@ -2250,7 +2302,7 @@
             int32_t setNumber = fRXPat->fSets->size();
             fRXPat->fSets->addElement(theSet, *fStatus);
             int32_t setOp = URX_BUILD(URX_SETREF, setNumber);
-            fRXPat->fCompiledPat->addElement(setOp, *fStatus);
+            appendOp(setOp);
         }
     }
 }
@@ -2289,11 +2341,8 @@
     //        counterLoc   -->  Loop counter
     //               +1    -->  Input index (for breaking non-progressing loops)
     //                          (Only present if unbounded upper limit on loop)
-    int32_t   counterLoc = fRXPat->fFrameSize;
-    fRXPat->fFrameSize++;
-    if (fIntervalUpper < 0) {
-        fRXPat->fFrameSize++;
-    }
+    int32_t   dataSize = fIntervalUpper < 0 ? 2 : 1;
+    int32_t   counterLoc = allocateStackData(dataSize);
 
     int32_t   op = URX_BUILD(InitOp, counterLoc);
     fRXPat->fCompiledPat->setElementAt(op, topOfBlock);
@@ -2313,7 +2362,7 @@
     // Apend the CTR_LOOP op.  The operand is the location of the CTR_INIT op.
     //   Goes at end of the block being looped over, so just append to the code so far.
     op = URX_BUILD(LoopOp, topOfBlock);
-    fRXPat->fCompiledPat->addElement(op, *fStatus);
+    appendOp(op);
 
     if ((fIntervalLow & 0xff000000) != 0 ||
         (fIntervalUpper > 0 && (fIntervalUpper & 0xff000000) != 0)) {
@@ -2380,12 +2429,12 @@
     int32_t i;
     for (i=1; i<fIntervalUpper; i++ ) {
         if (i == fIntervalLow) {
-            fRXPat->fCompiledPat->addElement(saveOp, *fStatus);
+            appendOp(saveOp);
         }
         if (i > fIntervalLow) {
-            fRXPat->fCompiledPat->addElement(saveOp, *fStatus);
+            appendOp(saveOp);
         }
-        fRXPat->fCompiledPat->addElement(op, *fStatus);
+        appendOp(op);
     }
     return TRUE;
 }
Index: source/i18n/regexcmp.h
===================================================================
--- source/i18n/regexcmp.h	(revision 292943)
+++ source/i18n/regexcmp.h	(working copy)
@@ -103,6 +103,11 @@
     void        fixLiterals(UBool split=FALSE);      // Generate code for pending literal characters.
     void        insertOp(int32_t where);             // Open up a slot for a new op in the
                                                      //   generated code at the specified location.
+    void        appendOp(int32_t op);                // Append a new op to the compiled pattern.
+    int32_t     allocateData(int32_t size);          // Allocate space in the matcher data area.
+                                                     //   Return index of the newly allocated data.
+    int32_t     allocateStackData(int32_t size);     // Allocate space in the match back-track stack frame.
+                                                     //   Return offset index in the frame.
     int32_t     minMatchLength(int32_t start,
                                int32_t end);
     int32_t     maxMatchLength(int32_t start,
Index: source/i18n/regeximp.cpp
===================================================================
--- source/i18n/regeximp.cpp	(revision 292709)
+++ source/i18n/regeximp.cpp	(working copy)
@@ -12,6 +12,8 @@
 
 #if !UCONFIG_NO_REGULAR_EXPRESSIONS
 #include "regeximp.h"
+
+#include "uassert.h"
 #include "unicode/utf16.h"
 
 U_NAMESPACE_BEGIN
@@ -113,7 +115,27 @@
     return fIndex;
 }
 
+// Assemble a pcode instruction from the opcode and operand values.
+// Out-of-range values should not occur - if they do it is from an internal
+// error in the regex compiler. 
 
+// TODO: move into regexcmp, where it has access to fStatus.
+//       NOP cleanly if U_FAILURE.
+//       Set U_REGEX_INTERNAL_ERROR on bad operands.
+
+int32_t URX_BUILD(int32_t type, int32_t val) {
+    if (type < 0 || type > 255) {
+        U_ASSERT(FALSE);
+        type = URX_RESERVED_OP;
+    }
+    if (val > 0x00ffffff) {
+        U_ASSERT(FALSE);
+        val = 0;
+    }
+    return (type << 24) | val;
+}
+
+
 U_NAMESPACE_END
 
 #endif
Index: source/i18n/regeximp.h
===================================================================
--- source/i18n/regeximp.h	(revision 292709)
+++ source/i18n/regeximp.h	(working copy)
@@ -254,7 +254,7 @@
 //
 //  Convenience macros for assembling and disassembling a compiled operation.
 //
-#define URX_BUILD(type, val) (int32_t)((type << 24) | (val))
+int32_t URX_BUILD(int32_t val, int32_t type);
 #define URX_TYPE(x)          ((uint32_t)(x) >> 24)
 #define URX_VAL(x)           ((x) & 0xffffff)
 
Index: source/test/intltest/regextst.cpp
===================================================================
--- source/test/intltest/regextst.cpp	(revision 292709)
+++ source/test/intltest/regextst.cpp	(working copy)
@@ -131,6 +131,9 @@
         case 21: name = "Bug 9283";
             if (exec) Bug9283();
             break;
+        case 22: name = "TestBug11371";
+            if (exec) TestBug11371();
+            break;
 
         default: name = "";
             break; //needed to end loop
@@ -5229,5 +5232,47 @@
   }
 }
 
+void RegexTest::TestBug11371() {
+    UErrorCode status = U_ZERO_ERROR;
+    UnicodeString patternString;
+
+    for (int i=0; i<8000000; i++) {
+        patternString.append(UnicodeString("()"));
+    }
+    LocalPointer<RegexPattern> compiledPat(RegexPattern::compile(patternString, 0, status));
+    if (status != U_REGEX_PATTERN_TOO_BIG) {
+        errln("File %s, line %d expected status=U_REGEX_PATTERN_TOO_BIG; got %s.",
+              __FILE__, __LINE__, u_errorName(status));
+    }
+
+    status = U_ZERO_ERROR;
+    patternString = "(";
+    for (int i=0; i<20000000; i++) {
+        patternString.append(UnicodeString("A++"));
+    }
+    patternString.append(UnicodeString("){0}B++"));
+    LocalPointer<RegexPattern> compiledPat2(RegexPattern::compile(patternString, 0, status));
+    if (status != U_REGEX_PATTERN_TOO_BIG) {
+        errln("File %s, line %d expected status=U_REGEX_PATTERN_TOO_BIG; got %s.",
+              __FILE__, __LINE__, u_errorName(status));
+    }
+
+    // Pattern with too much string data, such that string indexes overflow operand data.
+    status = U_ZERO_ERROR;
+    patternString = "";
+    while (patternString.length() < 0x00ffffff) {
+        patternString.append(UnicodeString("stuff and things dont you know, these are a few of my favorite strings\n"));
+    }
+    patternString.append(UnicodeString("X? trailing string"));
+    LocalPointer<RegexPattern> compiledPat3(RegexPattern::compile(patternString, 0, status));
+    compiledPat3->dumpPattern();
+    if (status != U_REGEX_PATTERN_TOO_BIG) {
+        errln("File %s, line %d expected status=U_REGEX_PATTERN_TOO_BIG; got %s.",
+              __FILE__, __LINE__, u_errorName(status));
+    }
+
+
+
+}
+
 #endif  /* !UCONFIG_NO_REGULAR_EXPRESSIONS  */
-
Index: source/test/intltest/regextst.h
===================================================================
--- source/test/intltest/regextst.h	(revision 292709)
+++ source/test/intltest/regextst.h	(working copy)
@@ -47,6 +47,7 @@
     virtual void Bug7029();
     virtual void Bug9283();
     virtual void CheckInvBufSize();
+    virtual void TestBug11371();
     
     // The following functions are internal to the regexp tests.
     virtual void assertUText(const char *expected, UText *actual, const char *file, int line);