BUG#28125030 - C/JAVA ASYNCHRONOUS XPLUGIN TESTS CAUSES CRASH IN MYSQL SERVER 8.0.12

Description
===========
Executing multithread test that uses an X Expression with cast operator,
causes a crash. The problem concerns Icu::RegexMatcher, which is neither
thread-safe nor re-entrant.

Fix
===
The fix allocates ice::RegexMatcher per thread.

RB: 19822
Reviewed-by: Tomasz Stepniak <[email protected]>
Reviewed-by: Grzegorz Szwarc <[email protected]>

Author: lkotula

plugin/x/src/xpl_regex.cc

@@ -22,20 +22,43 @@
 
 #include "plugin/x/src/xpl_regex.h"
 
+#include <memory>
+
 #include "include/my_dbug.h"
 
 namespace xpl {
 
 Regex::Regex(const char *const pattern)
     : m_status{U_ZERO_ERROR},
-      m_re{icu::UnicodeString::fromUTF8(pattern), UREGEX_CASE_INSENSITIVE,
-           m_status} {
+      m_pattern{icu::RegexPattern::compile(
+          icu::UnicodeString::fromUTF8(pattern), UREGEX_CASE_INSENSITIVE,
+          m_parse_error, m_status)} {
   DBUG_ASSERT(U_SUCCESS(m_status));
 }
 
 bool xpl::Regex::match(const char *value) const {
-  return U_SUCCESS(m_status) &&
-         m_re.reset(icu::UnicodeString::fromUTF8(value)).find(m_status);
+  if (!U_SUCCESS(m_status)) return false;
+
+  UErrorCode match_status{U_ZERO_ERROR};
+
+  /* Initializing RegexMatcher object with RegexPattern
+   * can by done only by calling an RegexPattern method
+   * that returns RegexMatcher pointer.
+   *
+   * RegexMatcher is not reentrant thus we need create an
+   * instance per thread or like in current solution,
+   * instance per xpl::Regex::match call.
+   *
+   * Other possibility would be to create RegexMatcher on stack
+   * and parse the text patter each time that xpl::Regex::match
+   * is called.
+   */
+  std::unique_ptr<icu::RegexMatcher> regexp{
+      m_pattern->matcher(icu::UnicodeString::fromUTF8(value), match_status)};
+
+  if (!U_SUCCESS(match_status)) return false;
+
+  return regexp->find();
 }
 
 }  // namespace xpl

plugin/x/src/xpl_regex.h

@@ -23,6 +23,8 @@
 #ifndef PLUGIN_X_SRC_XPL_REGEX_H_
 #define PLUGIN_X_SRC_XPL_REGEX_H_
 
+#include <memory>
+
 #include "unicode/regex.h"
 
 namespace xpl {
@@ -33,8 +35,18 @@ class Regex {
   bool match(const char *value) const;
 
  private:
-  mutable UErrorCode m_status;
-  mutable icu::RegexMatcher m_re;
+  UErrorCode m_status;
+  UParseError m_parse_error;
+  /* RegexPatter doesn't have public constructor
+   * that allow to initialize the object directly
+   * by the text patter. Only static method which
+   * returns an object pointer allows initialization
+   * text patter.
+   *
+   * We require here to have an smart-ptr/field
+   * instead a object/field.
+   */
+  std::unique_ptr<icu::RegexPattern> m_pattern;
 };
 }  // namespace xpl