The JIT compiler did not restore the control verb head in case of *THEN control verbs.

ChangeLog

@@ -108,6 +108,9 @@ character.
 28. If pcre2grep was given the -q option with -c or -l, or when handling a 
 binary file, it incorrectly wrote output to stdout.
 
+29. The JIT compiler did not restore the control verb head in case of *THEN
+control verbs. This issue was found by Karl Skomski with a custom LLVM fuzzer.
+
 
 Version 10.20 30-June-2015
 --------------------------

src/pcre2_jit_compile.c

@@ -1472,6 +1472,13 @@ while (cc < ccend)
     cc += 1 + LINK_SIZE + IMM2_SIZE;
     break;
 
+    case OP_THEN:
+    stack_restore = TRUE;
+    if (common->control_head_ptr != 0)
+      *needs_control_head = TRUE;
+    cc ++;
+    break;
+
     default:
     stack_restore = TRUE;
     /* Fall through. */

testdata/testinput2

@@ -4412,4 +4412,7 @@ a random value. /Ix
 
 /((?(R8000000000)))/
 
+/0(?0)|(1)(*THEN)(*SKIP:0)(*FAIL)/
+    01
+
 # End of testinput2 

testdata/testoutput2

@@ -14667,4 +14667,8 @@ Failed: error 161 at offset 13: number is too big
 /((?(R8000000000)))/
 Failed: error 161 at offset 16: number is too big
 
+/0(?0)|(1)(*THEN)(*SKIP:0)(*FAIL)/
+    01
+No match
+
 # End of testinput2