Fix \X after regional indicators and prepend characters

ChangeLog

@@ -22,6 +22,11 @@ backtracking after the recursive call.
 3. (#1040) Fixed the start_match field passed to interpreter callouts after \K
 resets the start of a match, including restoration on backtracking.
 
+4. Fixed \X so that an extended grapheme cluster continues after a regional
+indicator when extending characters, spacing marks or ZWJ follow (GB9 and GB9a
+in UAX #29), and after a prepend character when an Extended_Pictographic
+character follows (GB9b). Previously \X ended the cluster in both places.
+
 
 Version 10.49 28-September-2026
 -------------------------------

src/pcre2_tables.c

@@ -207,15 +207,15 @@ const uint32_t PRIV(ucp_gbtable)[] = {
   ESZ|(1u<<ucp_gbPrepend)|                             /*  4 Prepend */
       (1u<<ucp_gbL)|(1u<<ucp_gbV)|(1u<<ucp_gbT)|
       (1u<<ucp_gbLV)|(1u<<ucp_gbLVT)|(1u<<ucp_gbOther)|
-      (1u<<ucp_gbRegional_Indicator),
+      (1u<<ucp_gbRegional_Indicator)|(1u<<ucp_gbExtended_Pictographic),
   ESZ,                                                 /*  5 SpacingMark */
   ESZ|(1u<<ucp_gbL)|(1u<<ucp_gbV)|(1u<<ucp_gbLV)|      /*  6 L */
       (1u<<ucp_gbLVT),
   ESZ|(1u<<ucp_gbV)|(1u<<ucp_gbT),                     /*  7 V */
   ESZ|(1u<<ucp_gbT),                                   /*  8 T */
   ESZ|(1u<<ucp_gbV)|(1u<<ucp_gbT),                     /*  9 LV */
   ESZ|(1u<<ucp_gbT),                                   /* 10 LVT */
-  (1u<<ucp_gbRegional_Indicator),                      /* 11 Regional Indicator */
+  ESZ|(1u<<ucp_gbRegional_Indicator),                  /* 11 Regional Indicator */
   ESZ,                                                 /* 12 Other */
   ESZ|(1u<<ucp_gbExtended_Pictographic),               /* 13 ZWJ */
   ESZ,                                                 /* 14 Extended Pictographic */

testdata/testinput4

@@ -1632,7 +1632,14 @@
     \x{1F1E6}\x{1F1E7}\x{1F1E8}\x{1F1E9}B RegionalIndicator RegionalIndicator RegionalIndicator RegionalIndicator
     \x{200d}\x{1f308}B             ZWJ without Extended_Pictographic
     \x{261d}\x{200d}\x{1f308}B    Extended_Pictographic ZWJ Extended_Pictographic
-    *There are no Prepend characters, so we can't test Prepend, CR
+    *Test regional indicators followed by extend, spacing mark and ZWJ
+    \x{1F1E6}\x{300}B              RegionalIndicator Extend
+    \x{1F1E6}\x{903}B              RegionalIndicator SpacingMark
+    \x{1F1E6}\x{1F1E7}\x{200d}\x{1F1E8}B RegionalIndicator RegionalIndicator ZWJ RegionalIndicator
+    *Test Prepend
+    \x{6dd}\x{a9}B                 Prepend Extended_Pictographic
+    \x{600}AB                      Prepend Other
+    \x{600}\x{0d}B                 Prepend CR
 
 /^.\X/utf,aftertext
     A\x{1F1E6}\x{1F1E7}\x{1F1E8}B

testdata/testinput7

@@ -1739,7 +1739,14 @@
     \x0a\x{1b04}LF, spacingmark
     \x0b\x{0711}Control, extend
     \x09\x{1b04}Control, spacingmark
-\= There are no Prepend characters, so we can't test Prepend, CR
+\= Test regional indicators followed by extend, spacing mark and ZWJ
+    \x{1F1E6}\x{300}B              RegionalIndicator Extend
+    \x{1F1E6}\x{903}B              RegionalIndicator SpacingMark
+    \x{1F1E6}\x{1F1E7}\x{200d}\x{1F1E8}B RegionalIndicator RegionalIndicator ZWJ RegionalIndicator
+\= Test Prepend
+    \x{6dd}\x{a9}B                 Prepend Extended_Pictographic
+    \x{600}AB                      Prepend Other
+    \x{600}\x{0d}B                 Prepend CR
 
 /^(?>\X{2})X/utf,aftertext
     \x{1111}\x{ae4c}\x{1111}\x{ae4c}X

testdata/testoutput4

@@ -2733,9 +2733,30 @@ No match
     \x{261d}\x{200d}\x{1f308}B    Extended_Pictographic ZWJ Extended_Pictographic
  0: \x{261d}\x{200d}\x{1f308}
  0+ B    Extended_Pictographic ZWJ Extended_Pictographic
-    *There are no Prepend characters, so we can't test Prepend, CR
+    *Test regional indicators followed by extend, spacing mark and ZWJ
  0: *
- 0+ There are no Prepend characters, so we can't test Prepend, CR
+ 0+ Test regional indicators followed by extend, spacing mark and ZWJ
+    \x{1F1E6}\x{300}B              RegionalIndicator Extend
+ 0: \x{1f1e6}\x{300}
+ 0+ B              RegionalIndicator Extend
+    \x{1F1E6}\x{903}B              RegionalIndicator SpacingMark
+ 0: \x{1f1e6}\x{903}
+ 0+ B              RegionalIndicator SpacingMark
+    \x{1F1E6}\x{1F1E7}\x{200d}\x{1F1E8}B RegionalIndicator RegionalIndicator ZWJ RegionalIndicator
+ 0: \x{1f1e6}\x{1f1e7}\x{200d}
+ 0+ \x{1f1e8}B RegionalIndicator RegionalIndicator ZWJ RegionalIndicator
+    *Test Prepend
+ 0: *
+ 0+ Test Prepend
+    \x{6dd}\x{a9}B                 Prepend Extended_Pictographic
+ 0: \x{6dd}\x{a9}
+ 0+ B                 Prepend Extended_Pictographic
+    \x{600}AB                      Prepend Other
+ 0: \x{600}A
+ 0+ B                      Prepend Other
+    \x{600}\x{0d}B                 Prepend CR
+ 0: \x{600}
+ 0+ \x{0d}B                 Prepend CR
 
 /^.\X/utf,aftertext
     A\x{1F1E6}\x{1F1E7}\x{1F1E8}B

testdata/testoutput7

@@ -3036,7 +3036,26 @@ Partial match: AA
     \x09\x{1b04}Control, spacingmark
  0: \x{09}
  0+ \x{1b04}Control, spacingmark
-\= There are no Prepend characters, so we can't test Prepend, CR
+\= Test regional indicators followed by extend, spacing mark and ZWJ
+    \x{1F1E6}\x{300}B              RegionalIndicator Extend
+ 0: \x{1f1e6}\x{300}
+ 0+ B              RegionalIndicator Extend
+    \x{1F1E6}\x{903}B              RegionalIndicator SpacingMark
+ 0: \x{1f1e6}\x{903}
+ 0+ B              RegionalIndicator SpacingMark
+    \x{1F1E6}\x{1F1E7}\x{200d}\x{1F1E8}B RegionalIndicator RegionalIndicator ZWJ RegionalIndicator
+ 0: \x{1f1e6}\x{1f1e7}\x{200d}
+ 0+ \x{1f1e8}B RegionalIndicator RegionalIndicator ZWJ RegionalIndicator
+\= Test Prepend
+    \x{6dd}\x{a9}B                 Prepend Extended_Pictographic
+ 0: \x{6dd}\x{a9}
+ 0+ B                 Prepend Extended_Pictographic
+    \x{600}AB                      Prepend Other
+ 0: \x{600}A
+ 0+ B                      Prepend Other
+    \x{600}\x{0d}B                 Prepend CR
+ 0: \x{600}
+ 0+ \x{0d}B                 Prepend CR
 
 /^(?>\X{2})X/utf,aftertext
     \x{1111}\x{ae4c}\x{1111}\x{ae4c}X