MDEV-21058 CREATE TABLE with generated column and RLIKE results in sigabrt

Regexp_processor_pcre::fix_owner() called Regexp_processor_pcre::compile(),
which could fail on the regex syntax error in the pattern and put
an error into the diagnostics area. However, the callers:
  - Item_func_regex::fix_length_and_dec()
  - Item_func_regexp_instr::fix_length_and_dec()
still returned "false" in such cases, which made the code
crash later inside Diagnostics_area::set_ok_status().

Fix:

- Change the return type of fix_onwer() from "void" to "bool"
  and return "true" whenever an error is put to the DA
  (e.g. on the syntax error in the pattern).
- Fixing fix_length_and_dec() of the mentioned Item_func_xxx
  classes to return "true" if fix_onwer() returned "true".

mysql-test/main/func_regexp.result

@@ -192,4 +192,20 @@ SELECT SUM(a.t) FROM (SELECT (c1 RLIKE c1) = (c0 IS NULL) as t FROM t0) as a;
 SUM(a.t)
 0
 DROP TABLE t0;
+#
+# MDEV-21058 CREATE TABLE with generated column and RLIKE results in sigabrt
+#
+CREATE TABLE t1 (c0 INT);
+INSERT INTO t1 VALUES (1),(2),(3);
+SELECT ('' RLIKE '[') AS c1 FROM t1;
+ERROR 42000: Regex error 'missing terminating ] for character class at offset 1'
+SELECT REGEXP_INSTR('','[') AS c1 FROM t1;
+ERROR 42000: Regex error 'missing terminating ] for character class at offset 1'
+SELECT c0, '' RLIKE NULL AS c1, REGEXP_INSTR('', NULL) AS c2
+FROM t1 ORDER BY c0;
+c0	c1	c2
+1	NULL	NULL
+2	NULL	NULL
+3	NULL	NULL
+DROP TABLE t1;
 # End of 10.5 tests

mysql-test/main/func_regexp.test

@@ -132,5 +132,22 @@ SELECT (c1 RLIKE c1), (c0 IS NULL) FROM t0;
 SELECT SUM(a.t) FROM (SELECT (c1 RLIKE c1) = (c0 IS NULL) as t FROM t0) as a;
 DROP TABLE t0;
 
+--echo #
+--echo # MDEV-21058 CREATE TABLE with generated column and RLIKE results in sigabrt
+--echo #
+
+CREATE TABLE t1 (c0 INT);
+INSERT INTO t1 VALUES (1),(2),(3);
+
+--error ER_REGEXP_ERROR
+SELECT ('' RLIKE '[') AS c1 FROM t1;
+
+--error ER_REGEXP_ERROR
+SELECT REGEXP_INSTR('','[') AS c1 FROM t1;
+
+SELECT c0, '' RLIKE NULL AS c1, REGEXP_INSTR('', NULL) AS c2
+FROM t1 ORDER BY c0;
+
+DROP TABLE t1;
 
 --echo # End of 10.5 tests

mysql-test/suite/vcol/r/func_regexp.result

@@ -0,0 +1,24 @@
+#
+# Start of 10.5 tests
+#
+#
+# MDEV-21058 CREATE TABLE with generated column and RLIKE results in sigabrt
+#
+CREATE TABLE t1 (c0 INT AS(('' RLIKE '[')));
+ERROR 42000: Regex error 'missing terminating ] for character class at offset 1'
+CREATE TABLE t1 (c0 INT AS(REGEXP_INSTR('','[')));
+ERROR 42000: Regex error 'missing terminating ] for character class at offset 1'
+CREATE TABLE t1
+(
+c0 INT,
+c1 INT AS(('' RLIKE NULL)),
+c2 INT AS(REGEXP_INSTR('',NULL))
+);
+INSERT INTO t1 (c0) VALUES (0);
+SELECT * FROM t1;
+c0	c1	c2
+0	NULL	NULL
+DROP TABLE t1;
+#
+# End of 10.5 tests
+#

mysql-test/suite/vcol/t/func_regexp.test

@@ -0,0 +1,30 @@
+--source inc/vcol_init_vars.pre
+--source inc/vcol_cleanup.inc
+
+--echo #
+--echo # Start of 10.5 tests
+--echo #
+
+--echo #
+--echo # MDEV-21058 CREATE TABLE with generated column and RLIKE results in sigabrt
+--echo #
+
+--error ER_REGEXP_ERROR
+CREATE TABLE t1 (c0 INT AS(('' RLIKE '[')));
+
+--error ER_REGEXP_ERROR
+CREATE TABLE t1 (c0 INT AS(REGEXP_INSTR('','[')));
+
+CREATE TABLE t1
+(
+  c0 INT,
+  c1 INT AS(('' RLIKE NULL)),
+  c2 INT AS(REGEXP_INSTR('',NULL))
+);
+INSERT INTO t1 (c0) VALUES (0);
+SELECT * FROM t1;
+DROP TABLE t1;
+
+--echo #
+--echo # End of 10.5 tests
+--echo #

sql/item_cmpfunc.cc

@@ -6215,7 +6215,17 @@ bool Regexp_processor_pcre::exec(Item *item, int offset,
 }
 
 
-void Regexp_processor_pcre::fix_owner(Item_func *owner,
+/*
+  This method determines the owner's maybe_null flag.
+  Generally, the result is NULL-able. However, in case
+  of a constant pattern and a NOT NULL subject, the
+  result can also be NOT NULL.
+  @return  true - in case if the constant regex compilation failed
+           (e.g. due to a wrong regex syntax in the pattern).
+           The compilation error message is put to the DA in this case.
+           false - otherwise.
+*/
+bool Regexp_processor_pcre::fix_owner(Item_func *owner,
                                       Item *subject_arg,
                                       Item *pattern_arg)
 {
@@ -6223,16 +6233,30 @@ void Regexp_processor_pcre::fix_owner(Item_func *owner,
       pattern_arg->const_item() &&
       !pattern_arg->is_expensive())
   {
-    if (compile(pattern_arg, true))
+    if (compile(pattern_arg, true/* raise errors to DA, e.g. on bad syntax */))
     {
-      owner->maybe_null= 1; // Will always return NULL
+      owner->maybe_null= 1;
-      return;
+      if (pattern_arg->null_value)
+      {
+        /*
+          The pattern evaluated to NULL. Regex compilation did not happen.
+          No errors were put to DA. Continue with maybe_null==true.
+          The function will return NULL per row.
+        */
+        return false;
+      }
+      /*
+        A syntax error in the pattern, an error was raised to the DA.
+        Let's abort the query. The caller will send the error to the client.
+      */
+      return true;
     }
     set_const(true);
     owner->maybe_null= subject_arg->maybe_null;
   }
   else
     owner->maybe_null= 1;
+  return false;
 }
 
 
@@ -6244,8 +6268,7 @@ Item_func_regex::fix_length_and_dec()
     return TRUE;
 
   re.init(cmp_collation.collation, 0);
-  re.fix_owner(this, args[0], args[1]);
+  return re.fix_owner(this, args[0], args[1]);
-  return FALSE;
 }
 
 
@@ -6269,9 +6292,8 @@ Item_func_regexp_instr::fix_length_and_dec()
     return TRUE;
 
   re.init(cmp_collation.collation, 0);
-  re.fix_owner(this, args[0], args[1]);
   max_length= MY_INT32_NUM_DECIMAL_DIGITS; // See also Item_func_locate
-  return FALSE;
+  return re.fix_owner(this, args[0], args[1]);
 }
 
 

sql/item_cmpfunc.h

@@ -2893,7 +2893,7 @@ public:
   {}
   int default_regex_flags();
   void init(CHARSET_INFO *data_charset, int extra_flags);
-  void fix_owner(Item_func *owner, Item *subject_arg, Item *pattern_arg);
+  bool fix_owner(Item_func *owner, Item *subject_arg, Item *pattern_arg);
   bool compile(String *pattern, bool send_error);
   bool compile(Item *item, bool send_error);
   bool recompile(Item *item)