component_sys_var_service.cc

/* Copyright (c) 2017, 2025, Oracle and/or its affiliates.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License, version 2.0,
as published by the Free Software Foundation.

This program is designed to work with certain software (including
but not limited to OpenSSL) that is licensed under separate terms,
as designated in a particular file or component or in included license
documentation.  The authors of MySQL hereby grant you an additional
permission to link the program and your derivative works with the
separately licensed software that they have either included with
the program or referenced in the documentation.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License, version 2.0, for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */

#include <string.h>
#include <sys/types.h>
#include <memory>
#include <utility>

#include <mysql/components/minimal_chassis.h>
#include <mysql/components/services/log_builtins.h>
#include "component_sys_var_service_imp.h"
#include "lex_string.h"
#include "map_helpers.h"
#include "my_compiler.h"
#include "my_getopt.h"
#include "my_inttypes.h"
#include "my_macros.h"
#include "my_psi_config.h"
#include "my_sys.h"
#include "mysql/components/service_implementation.h"
#include "mysql/components/services/bits/psi_bits.h"
#include "mysql/components/services/bits/psi_memory_bits.h"
#include "mysql/components/services/component_sys_var_service.h"
#include "mysql/components/services/log_shared.h"
#include "mysql/components/services/system_variable_source_type.h"
#include "mysql/my_loglevel.h"
#include "mysql/psi/mysql_memory.h"
#include "mysql/psi/mysql_mutex.h"
#include "mysql/psi/mysql_rwlock.h"
#include "mysql/service_mysql_alloc.h"
#include "mysql/status_var.h"
#include "mysql/strings/dtoa.h"
#include "mysql/strings/m_ctype.h"
#include "mysql/udf_registration_types.h"
#include "mysqld_error.h"
#include "nulls.h"
#include "sql/current_thd.h"
#include "sql/error_handler.h"  // Internal_error_handler
#include "sql/log.h"
#include "sql/mysqld.h"
#include "sql/persisted_variable.h"  // Persisted_variables_cache
#include "sql/set_var.h"
#include "sql/sql_class.h"  // THD
#include "sql/sql_component.h"
#include "sql/sql_lex.h"  // LEX
#include "sql/sql_plugin_var.h"
#include "sql/sql_show.h"
#include "sql/sys_vars_shared.h"
#include "sql/thr_malloc.h"
#include "sql_string.h"
#include "strxmov.h"

#define FREE_RECORD(sysvar)                                              \
  my_free(const_cast<char *>(                                            \
      reinterpret_cast<sys_var_pluginvar *>(sysvar)->plugin_var->name)); \
  my_free(reinterpret_cast<sys_var_pluginvar *>(sysvar)->plugin_var);    \
  delete reinterpret_cast<sys_var_pluginvar *>(sysvar);

PSI_memory_key key_memory_comp_sys_var;

#ifdef HAVE_PSI_INTERFACE
static PSI_memory_info comp_sys_var_memory[] = {{&key_memory_comp_sys_var,
                                                 "component_system_variables",
                                                 0, 0, PSI_DOCUMENT_ME}};

void comp_sys_var_init_psi_keys(void) {
  const char *category = "component_sys_vars";
  int count;

  count = static_cast<int>(array_elements(comp_sys_var_memory));
  mysql_memory_register(category, comp_sys_var_memory, count);
}
#endif /* HAVE_PSI_INTERFACE */

void mysql_comp_sys_var_services_init() {
#ifdef HAVE_PSI_INTERFACE
  comp_sys_var_init_psi_keys();
#endif
  return;
}

int mysql_add_sysvar(sys_var *var) {
  assert(var->cast_pluginvar() != nullptr);
  /* A write lock should be held on LOCK_system_variables_hash */
  /* this fails if there is a conflicting variable name. see HASH_UNIQUE */
  mysql_mutex_assert_not_owner(&LOCK_plugin);
  mysql_rwlock_wrlock(&LOCK_system_variables_hash);
  if (!get_dynamic_system_variable_hash()
           ->emplace(to_string(var->name), var)
           .second) {
    LogErr(ERROR_LEVEL, ER_DUPLICATE_SYS_VAR, var->name.str);
    mysql_rwlock_unlock(&LOCK_system_variables_hash);
    return 1;
  }
  /* Update system_variable_hash version. */
  dynamic_system_variable_hash_version++;
  mysql_rwlock_unlock(&LOCK_system_variables_hash);
  return 0;
}

DEFINE_BOOL_METHOD(mysql_component_sys_variable_imp::register_variable,
                   (const char *component_name, const char *var_name, int flags,
                    const char *comment, mysql_sys_var_check_func check_func,
                    mysql_sys_var_update_func update_func, void *check_arg,
                    void *variable_value)) {
  try {
    struct sys_var_chain chain = {nullptr, nullptr};
    sys_var *sysvar [[maybe_unused]];
    char *com_sys_var_name, *optname, *com_sys_var_name_copy;
    int com_sys_var_len;
    SYS_VAR *opt = nullptr;
    my_option *opts = nullptr;
    bool ret = true;
    int opt_error;
    int *argc;
    char ***argv;
    int argc_copy;
    char **argv_copy;
    void *mem;
    get_opt_arg_source *opts_arg_source;
    THD *thd = current_thd;
    bool option_value_found_in_install = false;
    MEM_ROOT local_root{key_memory_comp_sys_var, 512};
    unsigned int offset = 0;

    com_sys_var_len = strlen(component_name) + strlen(var_name) + 2;
    com_sys_var_name = new (&local_root) char[com_sys_var_len];
    strxmov(com_sys_var_name, component_name, ".", var_name, NullS);
    my_casedn_str(&my_charset_latin1, com_sys_var_name);

    if (!(mem = my_multi_malloc(key_memory_comp_sys_var, MY_ZEROFILL, &opts,
                                (sizeof(my_option) * 2), &optname,
                                com_sys_var_len, &opts_arg_source,
                                sizeof(get_opt_arg_source), NULL))) {
      LogErr(ERROR_LEVEL, ER_SYS_VAR_COMPONENT_OOM, var_name);
      return ret;
    }

    strxmov(optname, component_name, ".", var_name, NullS);

    convert_underscore_to_dash(optname, com_sys_var_len - 1);

    opts->name = optname;
    opts->comment = comment;
    opts->id = 0;

    opts->arg_source = opts_arg_source;
    opts->arg_source->m_path_name[0] = 0;
    opts->arg_source->m_source = enum_variable_source::COMPILED;
    std::unique_ptr<SYS_VAR, decltype(&my_free)> unique_opt(nullptr, &my_free);

    switch (flags & PLUGIN_VAR_WITH_SIGN_TYPEMASK) {
      case PLUGIN_VAR_BOOL:
        if (flags & PLUGIN_VAR_THDLOCAL) {
          THDVAR_BOOL_TYPE(bool) * thdvar_bool;

          thdvar_bool = (thdvar_bool_type *)my_malloc(
              key_memory_comp_sys_var, sizeof(thdvar_bool_type), MYF(0));
          COPY_MYSQL_PLUGIN_THDVAR_HEADER(thdvar_bool, bool, check_func_bool,
                                          update_func_bool)

          BOOL_CHECK_ARG(bool) * bool_arg;
          bool_arg = (bool_check_arg_s *)check_arg;
          thdvar_bool->def_val = bool_arg->def_val;

          opt = (SYS_VAR *)thdvar_bool;
          ((thdvar_bool_type *)opt)->resolve = mysql_sys_var_bool;
        } else {
          SYSVAR_BOOL_TYPE(bool) * sysvar_bool;

          sysvar_bool = (sysvar_bool_type *)my_malloc(
              key_memory_comp_sys_var, sizeof(sysvar_bool_type), MYF(0));
          COPY_MYSQL_PLUGIN_VAR_HEADER(sysvar_bool, bool, check_func_bool,
                                       update_func_bool)

          BOOL_CHECK_ARG(bool) * bool_arg;
          bool_arg = (bool_check_arg_s *)check_arg;
          sysvar_bool->def_val = bool_arg->def_val;

          opt = (SYS_VAR *)sysvar_bool;
        }
        break;
      case PLUGIN_VAR_INT:
        if (flags & PLUGIN_VAR_THDLOCAL) {
          THDVAR_INTEGRAL_TYPE(int) * thdvar_int;
          thdvar_int = (thdvar_int_type *)my_malloc(
              key_memory_comp_sys_var, sizeof(thdvar_int_type), MYF(0));
          COPY_MYSQL_PLUGIN_THDVAR_HEADER(thdvar_int, int, check_func_int,
                                          update_func_int)

          INTEGRAL_CHECK_ARG(int) * int_arg;
          int_arg = (int_check_arg_s *)check_arg;
          COPY_MYSQL_PLUGIN_VAR_REMAINING(thdvar_int, int_arg)

          opt = (SYS_VAR *)thdvar_int;
          // All PLUGIN_VAR_INT variables are actually uint,
          // see struct System_variables
          // Except: plugin variables declared with MYSQL_THDVAR_INT,
          // which may actually be signed.
          ((thdvar_int_type *)opt)->resolve = mysql_sys_var_int;
        } else {
          SYSVAR_INTEGRAL_TYPE(int) * sysvar_int;
          sysvar_int = (sysvar_int_type *)my_malloc(
              key_memory_comp_sys_var, sizeof(sysvar_int_type), MYF(0));
          COPY_MYSQL_PLUGIN_VAR_HEADER(sysvar_int, int, check_func_int,
                                       update_func_int)

          INTEGRAL_CHECK_ARG(int) * int_arg;
          int_arg = (int_check_arg_s *)check_arg;
          COPY_MYSQL_PLUGIN_VAR_REMAINING(sysvar_int, int_arg)

          opt = (SYS_VAR *)sysvar_int;
        }
        break;
      case PLUGIN_VAR_INT | PLUGIN_VAR_UNSIGNED:
        if (flags & PLUGIN_VAR_THDLOCAL) {
          THDVAR_INTEGRAL_TYPE(uint) * thdvar_uint;
          thdvar_uint = (thdvar_uint_type *)my_malloc(
              key_memory_comp_sys_var, sizeof(thdvar_uint_type), MYF(0));
          COPY_MYSQL_PLUGIN_THDVAR_HEADER(thdvar_uint, uint, check_func_int,
                                          update_func_int)

          INTEGRAL_CHECK_ARG(uint) * uint_arg;
          uint_arg = (uint_check_arg_s *)check_arg;
          COPY_MYSQL_PLUGIN_VAR_REMAINING(thdvar_uint, uint_arg)

          opt = (SYS_VAR *)thdvar_uint;
          ((thdvar_uint_type *)opt)->resolve = mysql_sys_var_uint;
        } else {
          SYSVAR_INTEGRAL_TYPE(uint) * sysvar_uint;
          sysvar_uint = (sysvar_uint_type *)my_malloc(
              key_memory_comp_sys_var, sizeof(sysvar_uint_type), MYF(0));
          COPY_MYSQL_PLUGIN_VAR_HEADER(sysvar_uint, uint, check_func_int,
                                       update_func_int)

          INTEGRAL_CHECK_ARG(uint) * uint_arg;
          uint_arg = (uint_check_arg_s *)check_arg;
          COPY_MYSQL_PLUGIN_VAR_REMAINING(sysvar_uint, uint_arg)

          opt = (SYS_VAR *)sysvar_uint;
        }
        break;
      case PLUGIN_VAR_LONG:
        if (flags & PLUGIN_VAR_THDLOCAL) {
          THDVAR_INTEGRAL_TYPE(long) * thdvar_long;
          thdvar_long = (thdvar_long_type *)my_malloc(
              key_memory_comp_sys_var, sizeof(thdvar_long_type), MYF(0));
          COPY_MYSQL_PLUGIN_THDVAR_HEADER(thdvar_long, long, check_func_long,
                                          update_func_long)

          INTEGRAL_CHECK_ARG(long) * long_arg;
          long_arg = (long_check_arg_s *)check_arg;
          COPY_MYSQL_PLUGIN_VAR_REMAINING(thdvar_long, long_arg)

          opt = (SYS_VAR *)thdvar_long;
          // All PLUGIN_VAR_LONG variables are actually ulong,
          // see struct System_variables
          ((thdvar_ulong_t *)opt)->resolve = mysql_sys_var_ulong;
        } else {
          SYSVAR_INTEGRAL_TYPE(long) * sysvar_long;
          sysvar_long = (sysvar_long_type *)my_malloc(
              key_memory_comp_sys_var, sizeof(sysvar_long_type), MYF(0));
          COPY_MYSQL_PLUGIN_VAR_HEADER(sysvar_long, long, check_func_long,
                                       update_func_long)

          INTEGRAL_CHECK_ARG(long) * long_arg;
          long_arg = (long_check_arg_s *)check_arg;
          COPY_MYSQL_PLUGIN_VAR_REMAINING(sysvar_long, long_arg)

          opt = (SYS_VAR *)sysvar_long;
        }
        break;
      case PLUGIN_VAR_LONG | PLUGIN_VAR_UNSIGNED:
        if (flags & PLUGIN_VAR_THDLOCAL) {
          THDVAR_INTEGRAL_TYPE(ulong) * thdvar_ulong;
          thdvar_ulong = (thdvar_ulong_type *)my_malloc(
              key_memory_comp_sys_var, sizeof(thdvar_ulong_type), MYF(0));
          COPY_MYSQL_PLUGIN_THDVAR_HEADER(thdvar_ulong, ulong, check_func_long,
                                          update_func_long)

          INTEGRAL_CHECK_ARG(ulong) * ulong_arg;
          ulong_arg = (ulong_check_arg_s *)check_arg;
          COPY_MYSQL_PLUGIN_VAR_REMAINING(thdvar_ulong, ulong_arg)

          opt = (SYS_VAR *)thdvar_ulong;
          ((thdvar_ulong_type *)opt)->resolve = mysql_sys_var_ulong;
        } else {
          SYSVAR_INTEGRAL_TYPE(ulong) * sysvar_ulong;
          sysvar_ulong = (sysvar_ulong_type *)my_malloc(
              key_memory_comp_sys_var, sizeof(sysvar_ulong_type), MYF(0));
          COPY_MYSQL_PLUGIN_VAR_HEADER(sysvar_ulong, ulong, check_func_long,
                                       update_func_long)

          INTEGRAL_CHECK_ARG(ulong) * ulong_arg;
          ulong_arg = (ulong_check_arg_s *)check_arg;
          COPY_MYSQL_PLUGIN_VAR_REMAINING(sysvar_ulong, ulong_arg)

          opt = (SYS_VAR *)sysvar_ulong;
        }
        break;
      case PLUGIN_VAR_LONGLONG:
        if (flags & PLUGIN_VAR_THDLOCAL) {
          THDVAR_INTEGRAL_TYPE(longlong) * thdvar_longlong;
          thdvar_longlong = (thdvar_longlong_type *)my_malloc(
              key_memory_comp_sys_var, sizeof(thdvar_longlong_type), MYF(0));
          COPY_MYSQL_PLUGIN_THDVAR_HEADER(thdvar_longlong, longlong,
                                          check_func_longlong,
                                          update_func_longlong)

          INTEGRAL_CHECK_ARG(longlong) * longlong_arg;
          longlong_arg = (longlong_check_arg_s *)check_arg;
          COPY_MYSQL_PLUGIN_VAR_REMAINING(thdvar_longlong, longlong_arg)

          opt = (SYS_VAR *)thdvar_longlong;
          // All PLUGIN_VAR_LONGLONG variables are actually ulonglong,
          // see struct System_variables
          ((thdvar_ulonglong_t *)opt)->resolve = mysql_sys_var_ulonglong;
        } else {
          SYSVAR_INTEGRAL_TYPE(longlong) * sysvar_longlong;
          sysvar_longlong = (sysvar_longlong_type *)my_malloc(
              key_memory_comp_sys_var, sizeof(sysvar_longlong_type), MYF(0));
          COPY_MYSQL_PLUGIN_VAR_HEADER(sysvar_longlong, longlong,
                                       check_func_longlong,
                                       update_func_longlong)

          INTEGRAL_CHECK_ARG(longlong) * longlong_arg;
          longlong_arg = (longlong_check_arg_s *)check_arg;
          COPY_MYSQL_PLUGIN_VAR_REMAINING(sysvar_longlong, longlong_arg)

          opt = (SYS_VAR *)sysvar_longlong;
        }
        break;
      case PLUGIN_VAR_LONGLONG | PLUGIN_VAR_UNSIGNED:
        if (flags & PLUGIN_VAR_THDLOCAL) {
          THDVAR_INTEGRAL_TYPE(ulonglong) * thdvar_ulonglong;
          thdvar_ulonglong = (thdvar_ulonglong_type *)my_malloc(
              key_memory_comp_sys_var, sizeof(thdvar_ulonglong_type), MYF(0));
          COPY_MYSQL_PLUGIN_THDVAR_HEADER(thdvar_ulonglong, ulonglong,
                                          check_func_longlong,
                                          update_func_longlong)

          INTEGRAL_CHECK_ARG(ulonglong) * ulonglong_arg;
          ulonglong_arg = (ulonglong_check_arg_s *)check_arg;
          COPY_MYSQL_PLUGIN_VAR_REMAINING(thdvar_ulonglong, ulonglong_arg)

          opt = (SYS_VAR *)thdvar_ulonglong;
          ((thdvar_ulonglong_type *)opt)->resolve = mysql_sys_var_ulonglong;
        } else {
          SYSVAR_INTEGRAL_TYPE(ulonglong) * sysvar_ulonglong;
          sysvar_ulonglong = (sysvar_ulonglong_type *)my_malloc(
              key_memory_comp_sys_var, sizeof(sysvar_ulonglong_type), MYF(0));
          COPY_MYSQL_PLUGIN_VAR_HEADER(sysvar_ulonglong, ulonglong,
                                       check_func_longlong,
                                       update_func_longlong)

          INTEGRAL_CHECK_ARG(ulonglong) * ulonglong_arg;
          ulonglong_arg = (ulonglong_check_arg_s *)check_arg;
          COPY_MYSQL_PLUGIN_VAR_REMAINING(sysvar_ulonglong, ulonglong_arg)

          opt = (SYS_VAR *)sysvar_ulonglong;
        }
        break;
      case PLUGIN_VAR_STR:
        if (flags & PLUGIN_VAR_THDLOCAL) {
          THDVAR_STR_TYPE(str) * thdvar_str;
          thdvar_str = (thdvar_str_type *)my_malloc(
              key_memory_comp_sys_var, sizeof(thdvar_str_type), MYF(0));
          COPY_MYSQL_PLUGIN_THDVAR_HEADER(thdvar_str, char *, check_func_str,
                                          update_func_str)
          if (!update_func) {
            if (!(thdvar_str->flags &
                  (PLUGIN_VAR_MEMALLOC | PLUGIN_VAR_READONLY))) {
              thdvar_str->flags |= PLUGIN_VAR_READONLY;
              LogErr(WARNING_LEVEL, ER_SYS_VAR_COMPONENT_VARIABLE_SET_READ_ONLY,
                     var_name, component_name);
            }
          }

          STR_CHECK_ARG(str) * str_arg;
          str_arg = (str_check_arg_s *)check_arg;
          thdvar_str->def_val = str_arg->def_val;

          opt = (SYS_VAR *)thdvar_str;
          ((thdvar_str_type *)opt)->resolve = mysql_sys_var_str;
        } else {
          SYSVAR_STR_TYPE(str) * sysvar_str;
          sysvar_str = (sysvar_str_type *)my_malloc(
              key_memory_comp_sys_var, sizeof(sysvar_str_type), MYF(0));
          COPY_MYSQL_PLUGIN_VAR_HEADER(sysvar_str, char *, check_func_str,
                                       update_func_str)
          if (!update_func) {
            if (!(sysvar_str->flags &
                  (PLUGIN_VAR_MEMALLOC | PLUGIN_VAR_READONLY))) {
              sysvar_str->flags |= PLUGIN_VAR_READONLY;
              LogErr(WARNING_LEVEL, ER_SYS_VAR_COMPONENT_VARIABLE_SET_READ_ONLY,
                     var_name, component_name);
            }
          }

          STR_CHECK_ARG(str) * str_arg;
          str_arg = (str_check_arg_s *)check_arg;
          sysvar_str->def_val = str_arg->def_val;

          opt = (SYS_VAR *)sysvar_str;
        }
        break;
      case PLUGIN_VAR_ENUM:
        if (flags & PLUGIN_VAR_THDLOCAL) {
          THDVAR_ENUM_TYPE(enum) * thdvar_enum;
          thdvar_enum = (thdvar_enum_type *)my_malloc(
              key_memory_comp_sys_var, sizeof(thdvar_enum_type), MYF(0));
          COPY_MYSQL_PLUGIN_THDVAR_HEADER(thdvar_enum, ulong, check_func_enum,
                                          update_func_long)

          ENUM_CHECK_ARG(enum) * enum_arg;
          enum_arg = (enum_check_arg_s *)check_arg;
          thdvar_enum->def_val = enum_arg->def_val;
          thdvar_enum->typelib = enum_arg->typelib;

          opt = (SYS_VAR *)thdvar_enum;
          ((thdvar_enum_type *)opt)->resolve = mysql_sys_var_ulong;
        } else {
          SYSVAR_ENUM_TYPE(enum) * sysvar_enum;
          sysvar_enum = (sysvar_enum_type *)my_malloc(
              key_memory_comp_sys_var, sizeof(sysvar_enum_type), MYF(0));
          COPY_MYSQL_PLUGIN_VAR_HEADER(sysvar_enum, ulong, check_func_enum,
                                       update_func_long)

          ENUM_CHECK_ARG(enum) * enum_arg;
          enum_arg = (enum_check_arg_s *)check_arg;
          sysvar_enum->def_val = enum_arg->def_val;
          sysvar_enum->typelib = enum_arg->typelib;

          opt = (SYS_VAR *)sysvar_enum;
        }
        break;
      default:
        LogErr(ERROR_LEVEL, ER_SYS_VAR_COMPONENT_UNKNOWN_VARIABLE_TYPE, flags,
               component_name);
        goto end;
    }

    unique_opt.reset(opt);
    plugin_opt_set_limits(opts, opt);

    if ((flags & PLUGIN_VAR_THDLOCAL) &&
        register_var(component_name, var_name, flags)) {
      st_bookmark *var;
      if ((var = find_bookmark(component_name, var_name, flags))) {
        *(int *)(opt + 1) = offset = var->offset;
      }
    }

    if (flags & PLUGIN_VAR_THDLOCAL)
      opts->value = opts->u_max_value =
          (uchar **)(global_system_variables.dynamic_variables_ptr + offset);
    else
      opts->value = opts->u_max_value = *(uchar ***)(opt + 1);

    /*
      If this is executed by a SQL executing thread that is executing
      INSTALL COMPONENT
    */
    if (thd && thd->lex && thd->lex->m_sql_cmd &&
        thd->lex->m_sql_cmd->sql_command_code() == SQLCOM_INSTALL_COMPONENT) {
      Sql_cmd_install_component *c =
          down_cast<Sql_cmd_install_component *>(thd->lex->m_sql_cmd);
      /* and has a SET list */
      if (c->m_arg_list && c->m_arg_list_size > 1) {
        const int saved_opt_count = c->m_arg_list_size;
        argv = &c->m_arg_list;
        argc = &c->m_arg_list_size;
        opt_error =
            my_handle_options2(argc, argv, opts, nullptr, nullptr, false, true);
        /* Add back the program name handle_options removes */
        (*argc)++;
        (*argv)--;
        if (opt_error) {
          LogErr(ERROR_LEVEL,
                 ER_SYS_VAR_COMPONENT_FAILED_TO_PARSE_VARIABLE_OPTIONS,
                 var_name);
          if (opts) my_cleanup_options(opts);
          goto end;
        }
        option_value_found_in_install = (saved_opt_count > *argc);
      }
    }
    /*
      This does what plugins do:
      before the server is officially "started" the options are read
      (and consumed) from the remaining_argv/argc.
      The goal to that is that once the server is up all of the non-loose
      options (component and plugin) should be consumed and there should
      be an alarm sounded if any are remaining.
      This is approximately what plugin_register_early_plugins() and
      plugin_register_dynamic_and_init_all() are doing.
      Once the server is "started" we switch to the original list of options
      and copy them since handle_options() can modify the list.
      This is approximately what mysql_install_plugin() does.
      TODO: clean up the options processing code so all this is not needed.
    */
    if (!option_value_found_in_install) {
      if (mysqld_server_started) {
        Persisted_variables_cache *pv =
            Persisted_variables_cache::get_instance();
        argc_copy = argc_cached;
        argv_copy = new (&local_root) char *[argc_copy + 1];
        memcpy(argv_copy, argv_cached, (argc_copy + 1) * sizeof(char *));
        argc = &argc_copy;
        argv = &argv_copy;
        if (pv && pv->append_read_only_variables(argc, argv, true, true,
                                                 &local_root)) {
          LogErr(ERROR_LEVEL,
                 ER_SYS_VAR_COMPONENT_FAILED_TO_PARSE_VARIABLE_OPTIONS,
                 var_name);
          if (opts) my_cleanup_options(opts);
          goto end;
        }
      } else {
        argc = get_remaining_argc();
        argv = get_remaining_argv();
      }
      opt_error = handle_options(argc, argv, opts, nullptr);
      /* Add back the program name handle_options removes */
      (*argc)++;
      (*argv)--;

      if (opt_error) {
        LogErr(ERROR_LEVEL,
               ER_SYS_VAR_COMPONENT_FAILED_TO_PARSE_VARIABLE_OPTIONS, var_name);
        if (opts) my_cleanup_options(opts);
        goto end;
      }
    }

    com_sys_var_name_copy =
        my_strdup(key_memory_comp_sys_var, com_sys_var_name, MYF(0));
    if (com_sys_var_name_copy == nullptr) {
      LogErr(ERROR_LEVEL, ER_SYS_VAR_COMPONENT_OOM, var_name);
      goto end;
    }
    sysvar = reinterpret_cast<sys_var *>(
        new sys_var_pluginvar(&chain, com_sys_var_name_copy, opt));

    if (sysvar == nullptr) {
      LogErr(ERROR_LEVEL, ER_SYS_VAR_COMPONENT_OOM, var_name);
      goto end;
    } else
      unique_opt.release();

    sysvar->set_arg_source(opts->arg_source);
    sysvar->set_is_plugin(false);

    if (mysql_add_sysvar(chain.first)) {
      FREE_RECORD(sysvar)
      goto end;
    }

    /*
      Once server is started and if there are few persisted plugin variables
      which needs to be handled, we do it here. But only if it wasn't set by
      INSTALL COMPONENT
    */
    if (mysqld_server_started && !option_value_found_in_install) {
      Persisted_variables_cache *pv = Persisted_variables_cache::get_instance();
      if (pv != nullptr) {
        assert(thd != nullptr);

        mysql_rwlock_wrlock(&LOCK_system_variables_hash);
        mysql_mutex_lock(&LOCK_plugin);
        // ignore the SET PERSIST errors, as they're reported into the log
        class Error_to_warning_error_handler : public Internal_error_handler {
         public:
          bool handle_condition(THD *, uint, const char *,
                                Sql_condition::enum_severity_level *level,
                                const char *) override {
            if (*level == Sql_condition::SL_ERROR)
              *level = Sql_condition::SL_WARNING;
            return false;
          }
        } err_to_warning;
        thd->push_internal_handler(&err_to_warning);
        const bool error =
            pv->set_persisted_options(true, com_sys_var_name, com_sys_var_len);
        thd->pop_internal_handler();
        mysql_mutex_unlock(&LOCK_plugin);
        mysql_rwlock_unlock(&LOCK_system_variables_hash);
        if (error)
          LogErr(ERROR_LEVEL,
                 ER_SYS_VAR_COMPONENT_FAILED_TO_MAKE_VARIABLE_PERSISTENT,
                 com_sys_var_name);
      }
    }
    ret = false;

  end:
    my_free(mem);

    return ret;
  } catch (...) {
    mysql_components_handle_std_exception(__func__);
  }
  return true;
}

const char *get_variable_value(THD *thd, sys_var *system_var, char *val_buf,
                               enum_var_type var_type, size_t *val_length) {
  char show_var_buffer[sizeof(SHOW_VAR)];
  SHOW_VAR *show = (SHOW_VAR *)show_var_buffer;
  const CHARSET_INFO *fromcs;
  const CHARSET_INFO *tocs = &my_charset_utf8mb4_bin;
  uint dummy_err;
  /* buffer capable of storing all numeric values */
  char val_safe_buffer[FLOATING_POINT_BUFFER];
  char *variable_data_buffer = val_buf;
  size_t out_variable_data_length = 0;

  /*
     Function 'get_one_variable' converts numeric types into a string.
     User provides a buffer in which the string will be placed,
     still the function doesn't check buffer limits, thus there is a
     possibility of a buffer overflow.

     If user didn't provide a buffer large enough, then lets use
     our own buffer, and after we secured the conversion we will
     see if the string value can be placed in user buffer.
   */
  if (sizeof(val_safe_buffer) > *val_length) {
    variable_data_buffer = val_safe_buffer;
  }

  show->type = SHOW_SYS;
  show->name = system_var->name.str;
  show->value = (char *)system_var;

  mysql_mutex_lock(&LOCK_global_system_variables);
  const char *variable_value =
      get_one_variable(thd, show, var_type, show->type, nullptr, &fromcs,
                       variable_data_buffer, &out_variable_data_length);

  /*
     Allocate a buffer that can hold "worst" case byte-length of the value
     encoded using utf8mb4.
  */
  const size_t new_len =
      (tocs->mbmaxlen * out_variable_data_length) / fromcs->mbminlen + 1;
  std::unique_ptr<char[]> result(new char[new_len]);
  memset(result.get(), 0, new_len);
  const size_t result_length =
      copy_and_convert(result.get(), new_len, tocs, variable_value,
                       out_variable_data_length, fromcs, &dummy_err);
  mysql_mutex_unlock(&LOCK_global_system_variables);

  /*
     The length of the user supplied buffer is intentionally checked
     after conversion. Its because "new_len" defines worst case length,
     still the actual size is known after doing the calculation
     and in most cases it will be a lot less than "new_len".

     Please note that most optimistic(smallest) size will be following:

         (tocs->mbminlen * (len)) / fromcs->mbmaxlen
   */

  if (*val_length < result_length + 1) {  // "+1" is for terminating '\0'
    *val_length = result_length + 1;
    return nullptr;
  }

  *val_length = result_length;
  memcpy(val_buf, result.get(), result_length);
  val_buf[result_length] = '\0';

  return val_buf;
}

DEFINE_BOOL_METHOD(mysql_component_sys_variable_imp::get_variable,
                   (const char *component_name, const char *var_name,
                    void **val, size_t *out_length_of_val)) {
  try {
    // all of the non-prefixed variables are treated as part of the server
    // component
    const char *prefix =
        strcmp(component_name, "mysql_server") == 0 ? "" : component_name;
    auto f = [val, out_length_of_val](const System_variable_tracker &,
                                      sys_var *var) -> bool {
      return get_variable_value(current_thd, var, (char *)*val, OPT_GLOBAL,
                                out_length_of_val) == nullptr;
    };
    return System_variable_tracker::make_tracker(prefix, var_name)
        .access_system_variable<bool>(current_thd, f,
                                      Suppress_not_found_error::YES)
        .value_or(true);
  } catch (...) {
    mysql_components_handle_std_exception(__func__);
  }
  return true;
}

DEFINE_BOOL_METHOD(mysql_component_sys_variable_imp::unregister_variable,
                   (const char *component_name, const char *var_name)) {
  try {
    int result = 0;
    String com_sys_var_name;

    if (com_sys_var_name.reserve(strlen(component_name) + 1 + strlen(var_name) +
                                 1) ||
        com_sys_var_name.append(component_name) ||
        com_sys_var_name.append(".") || com_sys_var_name.append(var_name))
      return true;  // OOM
    if (current_thd != nullptr) {
      // During shutdown we have no THD, and we have already done
      // mysql_mutex_destroy(&LOCK_plugin);
      mysql_mutex_assert_not_owner(&LOCK_plugin);
    }
    mysql_rwlock_wrlock(&LOCK_system_variables_hash);

    sys_var *sysvar = nullptr;
    if (get_dynamic_system_variable_hash() != nullptr) {
      sysvar = find_or_nullptr(*get_dynamic_system_variable_hash(),
                               to_string(com_sys_var_name));
    }
    if (sysvar == nullptr) {
      LogErr(ERROR_LEVEL, ER_SYS_VAR_NOT_FOUND, com_sys_var_name.c_ptr());
      mysql_rwlock_unlock(&LOCK_system_variables_hash);
      return true;
    }

    result =
        !get_dynamic_system_variable_hash()->erase(to_string(sysvar->name));
    /* Update system_variable_hash version. */
    dynamic_system_variable_hash_version++;
    mysql_rwlock_unlock(&LOCK_system_variables_hash);

    /*
       Freeing the value of string variables if they have PLUGIN_VAR_MEMALLOC
       flag enabled while registering variables.
    */

    sys_var_pluginvar *sv_pluginvar =
        reinterpret_cast<sys_var_pluginvar *>(sysvar);

    const int var_flags = sv_pluginvar->plugin_var->flags;
    if (((var_flags & PLUGIN_VAR_TYPEMASK) == PLUGIN_VAR_STR) &&
        (var_flags & PLUGIN_VAR_MEMALLOC)) {
      /* Free the string from global_system_variables. */
      char **valptr =
          (char **)sv_pluginvar->real_value_ptr(nullptr, OPT_GLOBAL);
      if (*valptr != nullptr) {
        my_free(*valptr);
        *valptr = nullptr;
      }
    }

    FREE_RECORD(sysvar)

    return (result != 0);
  } catch (...) {
    mysql_components_handle_std_exception(__func__);
  }
  return true;
}