MDEV-29473 UBSAN: Signed integer overflow: X * Y cannot be represented in type 'int' in strings/dtoa.c

Fixing a few problems relealed by UBSAN in type_float.test

- multiplication overflow in dtoa.c

- uninitialized Field::geom_type (and Field::srid as well)

- Wrong call-back function types used in combination with SHOW_FUNC.
  Changes in the mysql_show_var_func data type definition were not
  properly addressed all around the code by the following commits:
    b4ff64568c88ab3ce559e7bd39853d9cbf86704a
    18feb62feeb833494d003615861b9c78ec008a90
    0ee879ff8ac1b80cd9a963015344f5698a81f309

  Adding a helper SHOW_FUNC_ENTRY() function and replacing
  all mysql_show_var_func declarations using SHOW_FUNC
  to SHOW_FUNC_ENTRY, to catch mysql_show_var_func in the future
  at compilation time.

17 files changed, 128 insertions, 29 deletions

diff --git a/include/myisampack.h b/include/myisampack.h
index 6bfe1958fbc..a7ba32b629c 100644
--- a/include/myisampack.h
+++ b/include/myisampack.h
@@ -30,7 +30,7 @@
 #define mi_uint1korr(A) ((uint8)(*A))
 
 #define mi_sint2korr(A) ((int16) (((int16) (((const uchar*) (A))[1])) |\
-                                  ((int16) ((int16) ((const char*) (A))[0]) << 8)))
+                                  ((int16) ((uint16) ((const uchar*) (A))[0]) << 8)))
 #define mi_sint3korr(A) ((int32) (((((const uchar*) (A))[0]) & 128) ? \
                                   (((uint32) 255L << 24) | \
                                    (((uint32) ((const uchar*) (A))[0]) << 16) |\
diff --git a/include/mysql/plugin.h b/include/mysql/plugin.h
index 360f633b7dd..b15f42fe6c7 100644
--- a/include/mysql/plugin.h
+++ b/include/mysql/plugin.h
@@ -200,6 +200,18 @@ struct system_status_var;
 typedef int (*mysql_show_var_func)(MYSQL_THD, struct st_mysql_show_var*, void *, struct system_status_var *status_var, enum enum_var_type);
 
 
+static inline
+struct st_mysql_show_var SHOW_FUNC_ENTRY(const char *name,
+                                         mysql_show_var_func func_arg)
+{
+  struct st_mysql_show_var tmp;
+  tmp.name= name;
+  tmp.value= (void*) func_arg;
+  tmp.type= SHOW_FUNC;
+  return tmp;
+};
+
+
 /*
   Constants for plugin flags.
  */
diff --git a/include/mysql/plugin_audit.h.pp b/include/mysql/plugin_audit.h.pp
index 89f7dcc36c4..b8cafee28ec 100644
--- a/include/mysql/plugin_audit.h.pp
+++ b/include/mysql/plugin_audit.h.pp
@@ -400,6 +400,16 @@ struct st_mysql_show_var {
 };
 struct system_status_var;
 typedef int (*mysql_show_var_func)(void*, struct st_mysql_show_var*, void *, struct system_status_var *status_var, enum enum_var_type);
+static inline
+struct st_mysql_show_var SHOW_FUNC_ENTRY(const char *name,
+                                         mysql_show_var_func func_arg)
+{
+  struct st_mysql_show_var tmp;
+  tmp.name= name;
+  tmp.value= (void*) func_arg;
+  tmp.type= SHOW_FUNC;
+  return tmp;
+};
 struct st_mysql_sys_var;
 struct st_mysql_value;
 typedef int (*mysql_var_check_func)(void* thd,
diff --git a/include/mysql/plugin_auth.h.pp b/include/mysql/plugin_auth.h.pp
index e515699cad6..68e2bcb9956 100644
--- a/include/mysql/plugin_auth.h.pp
+++ b/include/mysql/plugin_auth.h.pp
@@ -400,6 +400,16 @@ struct st_mysql_show_var {
 };
 struct system_status_var;
 typedef int (*mysql_show_var_func)(void*, struct st_mysql_show_var*, void *, struct system_status_var *status_var, enum enum_var_type);
+static inline
+struct st_mysql_show_var SHOW_FUNC_ENTRY(const char *name,
+                                         mysql_show_var_func func_arg)
+{
+  struct st_mysql_show_var tmp;
+  tmp.name= name;
+  tmp.value= (void*) func_arg;
+  tmp.type= SHOW_FUNC;
+  return tmp;
+};
 struct st_mysql_sys_var;
 struct st_mysql_value;
 typedef int (*mysql_var_check_func)(void* thd,
diff --git a/include/mysql/plugin_encryption.h.pp b/include/mysql/plugin_encryption.h.pp
index 7defe0aec2c..838d0e49ed5 100644
--- a/include/mysql/plugin_encryption.h.pp
+++ b/include/mysql/plugin_encryption.h.pp
@@ -400,6 +400,16 @@ struct st_mysql_show_var {
 };
 struct system_status_var;
 typedef int (*mysql_show_var_func)(void*, struct st_mysql_show_var*, void *, struct system_status_var *status_var, enum enum_var_type);
+static inline
+struct st_mysql_show_var SHOW_FUNC_ENTRY(const char *name,
+                                         mysql_show_var_func func_arg)
+{
+  struct st_mysql_show_var tmp;
+  tmp.name= name;
+  tmp.value= (void*) func_arg;
+  tmp.type= SHOW_FUNC;
+  return tmp;
+};
 struct st_mysql_sys_var;
 struct st_mysql_value;
 typedef int (*mysql_var_check_func)(void* thd,
diff --git a/include/mysql/plugin_ftparser.h.pp b/include/mysql/plugin_ftparser.h.pp
index a36f51e74e1..3c28bd3b2e0 100644
--- a/include/mysql/plugin_ftparser.h.pp
+++ b/include/mysql/plugin_ftparser.h.pp
@@ -400,6 +400,16 @@ struct st_mysql_show_var {
 };
 struct system_status_var;
 typedef int (*mysql_show_var_func)(void*, struct st_mysql_show_var*, void *, struct system_status_var *status_var, enum enum_var_type);
+static inline
+struct st_mysql_show_var SHOW_FUNC_ENTRY(const char *name,
+                                         mysql_show_var_func func_arg)
+{
+  struct st_mysql_show_var tmp;
+  tmp.name= name;
+  tmp.value= (void*) func_arg;
+  tmp.type= SHOW_FUNC;
+  return tmp;
+};
 struct st_mysql_sys_var;
 struct st_mysql_value;
 typedef int (*mysql_var_check_func)(void* thd,
diff --git a/include/mysql/plugin_password_validation.h.pp b/include/mysql/plugin_password_validation.h.pp
index 9701ad1b92f..bf05ca36351 100644
--- a/include/mysql/plugin_password_validation.h.pp
+++ b/include/mysql/plugin_password_validation.h.pp
@@ -400,6 +400,16 @@ struct st_mysql_show_var {
 };
 struct system_status_var;
 typedef int (*mysql_show_var_func)(void*, struct st_mysql_show_var*, void *, struct system_status_var *status_var, enum enum_var_type);
+static inline
+struct st_mysql_show_var SHOW_FUNC_ENTRY(const char *name,
+                                         mysql_show_var_func func_arg)
+{
+  struct st_mysql_show_var tmp;
+  tmp.name= name;
+  tmp.value= (void*) func_arg;
+  tmp.type= SHOW_FUNC;
+  return tmp;
+};
 struct st_mysql_sys_var;
 struct st_mysql_value;
 typedef int (*mysql_var_check_func)(void* thd,
diff --git a/mysql-test/main/type_float.result b/mysql-test/main/type_float.result
index a5f70d9ef80..5354fa50e19 100644
--- a/mysql-test/main/type_float.result
+++ b/mysql-test/main/type_float.result
@@ -964,5 +964,12 @@ id	a
 DELETE FROM t1 WHERE a=CAST(0.671437 AS FLOAT);
 DROP TABLE t1;
 #
+# MDEV-29473 UBSAN: Signed integer overflow: X * Y cannot be represented in type 'int' in strings/dtoa.c
+#
+CREATE TABLE t1 (c DOUBLE);
+INSERT INTO t1 VALUES ('1e4294967297');
+ERROR 22003: Out of range value for column 'c' at row 1
+DROP TABLE t1;
+#
 # End of 10.3 tests
 #
diff --git a/mysql-test/main/type_float.test b/mysql-test/main/type_float.test
index 5d7f7de7d0b..3f9781e6224 100644
--- a/mysql-test/main/type_float.test
+++ b/mysql-test/main/type_float.test
@@ -670,6 +670,16 @@ SELECT * FROM t1;
 DELETE FROM t1 WHERE a=CAST(0.671437 AS FLOAT);
 DROP TABLE t1;
 
+--echo #
+--echo # MDEV-29473 UBSAN: Signed integer overflow: X * Y cannot be represented in type 'int' in strings/dtoa.c
+--echo #
+
+# This test was failing with UBSAN builds
+
+CREATE TABLE t1 (c DOUBLE);
+--error ER_WARN_DATA_OUT_OF_RANGE
+INSERT INTO t1 VALUES ('1e4294967297');
+DROP TABLE t1;
 
 --echo #
 --echo # End of 10.3 tests
diff --git a/plugin/handler_socket/handlersocket/handlersocket.cpp b/plugin/handler_socket/handlersocket/handlersocket.cpp
index 8133497044c..45c9e13b2ca 100644
--- a/plugin/handler_socket/handlersocket/handlersocket.cpp
+++ b/plugin/handler_socket/handlersocket/handlersocket.cpp
@@ -185,7 +185,9 @@ static SHOW_VAR hs_status_variables[] = {
   {NullS, NullS, SHOW_LONG}
 };
 
-static int show_hs_vars(THD *thd, SHOW_VAR *var, char *buff)
+static int show_hs_vars(THD *thd, SHOW_VAR *var, void *buff,
+                        struct system_status_var *status_var,
+                        enum enum_var_type var_type)
 {
   var->type= SHOW_ARRAY;
   var->value= (char *) &hs_status_variables;
@@ -193,7 +195,7 @@ static int show_hs_vars(THD *thd, SHOW_VAR *var, char *buff)
 }
 
 static SHOW_VAR daemon_handlersocket_status_variables[] = {
-  {"Hs", (char*) show_hs_vars, SHOW_FUNC},
+  SHOW_FUNC_ENTRY("Hs", &show_hs_vars),
   {NullS, NullS, SHOW_LONG}
 };
 
diff --git a/sql/field.cc b/sql/field.cc
index f430e6209d5..43514347106 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -11073,6 +11073,8 @@ bool Field_vers_trx_id::test_if_equality_guarantees_uniqueness(const Item* item)
 Column_definition::Column_definition(THD *thd, Field *old_field,
                                                Field *orig_field)
 {
+  geom_type= Field::GEOM_GEOMETRY;
+  srid= 0;
   on_update=  NULL;
   field_name= old_field->field_name;
   length=     old_field->field_length;
diff --git a/sql/log.cc b/sql/log.cc
index 7ca9b38dc6e..4b071f133f7 100644
--- a/sql/log.cc
+++ b/sql/log.cc
@@ -10501,7 +10501,7 @@ static int show_binlog_vars(THD *thd, SHOW_VAR *var, void *,
 }
 
 static SHOW_VAR binlog_status_vars_top[]= {
-  {"Binlog", (char *) &show_binlog_vars, SHOW_FUNC},
+  SHOW_FUNC_ENTRY("Binlog", &show_binlog_vars),
   {NullS, NullS, SHOW_LONG}
 };
 
diff --git a/sql/mysqld.cc b/sql/mysqld.cc
index 84c3b9fb0a6..d58f2ed557f 100644
--- a/sql/mysqld.cc
+++ b/sql/mysqld.cc
@@ -8395,7 +8395,9 @@ static int show_ssl_get_cipher_list(THD *thd, SHOW_VAR *var, char *buff,
     rpl_semi_sync_master_show_##name
 
 #define DEF_SHOW_FUNC(name, show_type)                                       \
-    static  int SHOW_FNAME(name)(MYSQL_THD thd, SHOW_VAR *var, char *buff)   \
+    static  int SHOW_FNAME(name)(MYSQL_THD thd, SHOW_VAR *var, void *buff,   \
+                                 system_status_var *status_var,              \
+                                 enum_var_type var_type)                     \
     {                                                                        \
       repl_semisync_master.set_export_stats();                                 \
       var->type= show_type;                                                  \
@@ -8661,7 +8663,7 @@ SHOW_VAR status_vars[]= {
   {"Created_tmp_files",	       (char*) &my_tmp_file_created,	SHOW_LONG},
   {"Created_tmp_tables",       (char*) offsetof(STATUS_VAR, created_tmp_tables_), SHOW_LONG_STATUS},
 #ifndef DBUG_OFF
-  {"Debug",                    (char*) &debug_status_func,  SHOW_FUNC},
+  SHOW_FUNC_ENTRY("Debug",     &debug_status_func),
 #endif
   {"Delayed_errors",           (char*) &delayed_insert_errors,  SHOW_LONG},
   {"Delayed_insert_threads",   (char*) &delayed_insert_threads, SHOW_LONG_NOFLUSH},
@@ -8713,7 +8715,7 @@ SHOW_VAR status_vars[]= {
   {"Handler_tmp_write",        (char*) offsetof(STATUS_VAR, ha_tmp_write_count), SHOW_LONG_STATUS},
   {"Handler_update",           (char*) offsetof(STATUS_VAR, ha_update_count), SHOW_LONG_STATUS},
   {"Handler_write",            (char*) offsetof(STATUS_VAR, ha_write_count), SHOW_LONG_STATUS},
-  {"Key",                      (char*) &show_default_keycache, SHOW_FUNC},
+  SHOW_FUNC_ENTRY("Key",       &show_default_keycache),
   {"Last_query_cost",          (char*) offsetof(STATUS_VAR, last_query_cost), SHOW_DOUBLE_STATUS},
   {"Max_statement_time_exceeded", (char*) offsetof(STATUS_VAR, max_statement_time_exceeded), SHOW_LONG_STATUS},
   {"Master_gtid_wait_count",   (char*) offsetof(STATUS_VAR, master_gtid_wait_count), SHOW_LONG_STATUS},
@@ -8737,20 +8739,20 @@ SHOW_VAR status_vars[]= {
   {"Rows_read",                (char*) offsetof(STATUS_VAR, rows_read), SHOW_LONGLONG_STATUS},
   {"Rows_tmp_read",            (char*) offsetof(STATUS_VAR, rows_tmp_read), SHOW_LONGLONG_STATUS},
 #ifdef HAVE_REPLICATION
-  {"Rpl_semi_sync_master_status", (char*) &SHOW_FNAME(status), SHOW_FUNC},
-  {"Rpl_semi_sync_master_clients", (char*) &SHOW_FNAME(clients), SHOW_FUNC},
+  SHOW_FUNC_ENTRY("Rpl_semi_sync_master_status", &SHOW_FNAME(status)),
+  SHOW_FUNC_ENTRY("Rpl_semi_sync_master_clients", &SHOW_FNAME(clients)),
   {"Rpl_semi_sync_master_yes_tx", (char*) &rpl_semi_sync_master_yes_transactions, SHOW_LONG},
   {"Rpl_semi_sync_master_no_tx", (char*) &rpl_semi_sync_master_no_transactions, SHOW_LONG},
-  {"Rpl_semi_sync_master_wait_sessions", (char*) &SHOW_FNAME(wait_sessions), SHOW_FUNC},
+  SHOW_FUNC_ENTRY("Rpl_semi_sync_master_wait_sessions", &SHOW_FNAME(wait_sessions)),
   {"Rpl_semi_sync_master_no_times", (char*) &rpl_semi_sync_master_off_times, SHOW_LONG},
   {"Rpl_semi_sync_master_timefunc_failures", (char*) &rpl_semi_sync_master_timefunc_fails, SHOW_LONG},
   {"Rpl_semi_sync_master_wait_pos_backtraverse", (char*) &rpl_semi_sync_master_wait_pos_backtraverse, SHOW_LONG},
-  {"Rpl_semi_sync_master_tx_wait_time", (char*) &SHOW_FNAME(trx_wait_time), SHOW_FUNC},
-  {"Rpl_semi_sync_master_tx_waits", (char*) &SHOW_FNAME(trx_wait_num), SHOW_FUNC},
-  {"Rpl_semi_sync_master_tx_avg_wait_time", (char*) &SHOW_FNAME(avg_trx_wait_time), SHOW_FUNC},
-  {"Rpl_semi_sync_master_net_wait_time", (char*) &SHOW_FNAME(net_wait_time), SHOW_FUNC},
-  {"Rpl_semi_sync_master_net_waits", (char*) &SHOW_FNAME(net_wait_num), SHOW_FUNC},
-  {"Rpl_semi_sync_master_net_avg_wait_time", (char*) &SHOW_FNAME(avg_net_wait_time), SHOW_FUNC},
+  SHOW_FUNC_ENTRY("Rpl_semi_sync_master_tx_wait_time", &SHOW_FNAME(trx_wait_time)),
+  SHOW_FUNC_ENTRY("Rpl_semi_sync_master_tx_waits", &SHOW_FNAME(trx_wait_num)),
+  SHOW_FUNC_ENTRY("Rpl_semi_sync_master_tx_avg_wait_time", &SHOW_FNAME(avg_trx_wait_time)),
+  SHOW_FUNC_ENTRY("Rpl_semi_sync_master_net_wait_time", &SHOW_FNAME(net_wait_time)),
+  SHOW_FUNC_ENTRY("Rpl_semi_sync_master_net_waits", &SHOW_FNAME(net_wait_num)),
+  SHOW_FUNC_ENTRY("Rpl_semi_sync_master_net_avg_wait_time", &SHOW_FNAME(avg_net_wait_time)),
   {"Rpl_semi_sync_master_request_ack", (char*) &rpl_semi_sync_master_request_ack, SHOW_LONGLONG},
   {"Rpl_semi_sync_master_get_ack", (char*)&rpl_semi_sync_master_get_ack, SHOW_LONGLONG},
   {"Rpl_semi_sync_slave_status", (char*) &rpl_semi_sync_slave_status, SHOW_BOOL},
@@ -8858,7 +8860,7 @@ SHOW_VAR status_vars[]= {
   {"Uptime_since_flush_status",(char*) &show_flushstatustime,   SHOW_SIMPLE_FUNC},
 #endif
 #ifdef WITH_WSREP
-  {"wsrep",                    (char*) &wsrep_show_status,       SHOW_FUNC},
+  SHOW_FUNC_ENTRY("wsrep",     &wsrep_show_status),
 #endif
   {NullS, NullS, SHOW_LONG}
 };
diff --git a/storage/innobase/handler/ha_innodb.cc b/storage/innobase/handler/ha_innodb.cc
index cd2d36df112..81236343642 100644
--- a/storage/innobase/handler/ha_innodb.cc
+++ b/storage/innobase/handler/ha_innodb.cc
@@ -18415,7 +18415,9 @@ innodb_enable_monitor_at_startup(
 /****************************************************************//**
 Callback function for accessing the InnoDB variables from MySQL:
 SHOW VARIABLES. */
-static int show_innodb_vars(THD*, SHOW_VAR* var, char*)
+static int show_innodb_vars(THD*, SHOW_VAR* var, void *,
+                            struct system_status_var *status_var,
+                            enum enum_var_type var_type)
 {
 	innodb_export_status();
 	var->type = SHOW_ARRAY;
@@ -18861,7 +18863,7 @@ innobase_debug_sync_set(THD *thd, st_mysql_sys_var*, void *, const void *value)
 #endif
 
 static SHOW_VAR innodb_status_variables_export[]= {
-	{"Innodb", (char*) &show_innodb_vars, SHOW_FUNC},
+	SHOW_FUNC_ENTRY("Innodb", &show_innodb_vars),
 	{NullS, NullS, SHOW_LONG}
 };
 
diff --git a/storage/rocksdb/ha_rocksdb.cc b/storage/rocksdb/ha_rocksdb.cc
index cd366a12462..aa934695322 100644
--- a/storage/rocksdb/ha_rocksdb.cc
+++ b/storage/rocksdb/ha_rocksdb.cc
@@ -13102,7 +13102,9 @@ bool ha_rocksdb::commit_inplace_alter_table(
 #define SHOW_FNAME(name) rocksdb_show_##name
 
 #define DEF_SHOW_FUNC(name, key)                                           \
-  static int SHOW_FNAME(name)(MYSQL_THD thd, SHOW_VAR * var, char *buff) { \
+  static int SHOW_FNAME(name)(MYSQL_THD thd, SHOW_VAR * var, void *buff,   \
+                              struct system_status_var *status_var,        \
+                              enum enum_var_type var_type) {               \
     rocksdb_status_counters.name =                                         \
         rocksdb_stats->getTickerCount(rocksdb::key);                       \
     var->type = SHOW_LONGLONG;                                             \
@@ -13111,7 +13113,7 @@ bool ha_rocksdb::commit_inplace_alter_table(
   }
 
 #define DEF_STATUS_VAR(name) \
-  { "rocksdb_" #name, (char *)&SHOW_FNAME(name), SHOW_FUNC }
+  SHOW_FUNC_ENTRY( "rocksdb_" #name, &SHOW_FNAME(name))
 
 #define DEF_STATUS_VAR_PTR(name, ptr, option) \
   { "rocksdb_" name, (char *)ptr, option }
@@ -13339,11 +13341,14 @@ static SHOW_VAR myrocks_status_variables[] = {
 
     {NullS, NullS, SHOW_LONG}};
 
-static void show_myrocks_vars(THD *thd, SHOW_VAR *var, char *buff) {
+static int show_myrocks_vars(THD *thd, SHOW_VAR *var, void *buff,
+                             struct system_status_var *,
+                             enum enum_var_type) {
   myrocks_update_status();
   myrocks_update_memory_status();
   var->type = SHOW_ARRAY;
   var->value = reinterpret_cast<char *>(&myrocks_status_variables);
+  return 0;
 }
 
 static ulonglong io_stall_prop_value(
@@ -13424,10 +13429,13 @@ static SHOW_VAR rocksdb_stall_status_variables[] = {
     // end of the array marker
     {NullS, NullS, SHOW_LONG}};
 
-static void show_rocksdb_stall_vars(THD *thd, SHOW_VAR *var, char *buff) {
+static int show_rocksdb_stall_vars(THD *thd, SHOW_VAR *var, void *buff,
+                                   struct system_status_var *,
+                                   enum enum_var_type) {
   update_rocksdb_stall_status();
   var->type = SHOW_ARRAY;
   var->value = reinterpret_cast<char *>(&rocksdb_stall_status_variables);
+  return 0;
 }
 
 static SHOW_VAR rocksdb_status_vars[] = {
@@ -13532,9 +13540,8 @@ static SHOW_VAR rocksdb_status_vars[] = {
     // the variables generated by SHOW_FUNC are sorted only by prefix (first
     // arg in the tuple below), so make sure it is unique to make sorting
     // deterministic as quick sort is not stable
-    {"rocksdb", reinterpret_cast<char *>(&show_myrocks_vars), SHOW_FUNC},
-    {"rocksdb_stall", reinterpret_cast<char *>(&show_rocksdb_stall_vars),
-     SHOW_FUNC},
+    SHOW_FUNC_ENTRY("rocksdb", &show_myrocks_vars),
+    SHOW_FUNC_ENTRY("rocksdb_stall", &show_rocksdb_stall_vars),
     {NullS, NullS, SHOW_LONG}};
 
 /*
diff --git a/storage/tokudb/hatoku_hton.cc b/storage/tokudb/hatoku_hton.cc
index 81355ea20ff..79ca28188ac 100644
--- a/storage/tokudb/hatoku_hton.cc
+++ b/storage/tokudb/hatoku_hton.cc
@@ -1894,7 +1894,9 @@ static void tokudb_lock_wait_needed_callback(
 // and prefixed with "TOKUDB_"
 static int show_tokudb_vars(TOKUDB_UNUSED(THD* thd),
                             SHOW_VAR* var,
-                            TOKUDB_UNUSED(char* buff)) {
+                            TOKUDB_UNUSED(void* buff),
+                            TOKUDB_UNUSED(system_status_var *status_var),
+                            TOKUDB_UNUSED(enum_var_type var_type)) {
     TOKUDB_DBUG_ENTER("");
 
     int error;
@@ -1994,7 +1996,7 @@ static int show_tokudb_vars(TOKUDB_UNUSED(THD* thd),
 }
 
 static SHOW_VAR toku_global_status_variables_export[]= {
-    {"Tokudb", (char*)&show_tokudb_vars, SHOW_FUNC},
+    SHOW_FUNC_ENTRY("Tokudb", &show_tokudb_vars),
     {NullS, NullS, SHOW_LONG}
 };
 
diff --git a/strings/dtoa.c b/strings/dtoa.c
index e31b7e92d7c..13e28821f69 100644
--- a/strings/dtoa.c
+++ b/strings/dtoa.c
@@ -1478,7 +1478,10 @@ static double my_strtod_int(const char *s00, char **se, int *error, char *buf, s
         L= c - '0';
         s1= s;
         while (++s < end && (c= *s) >= '0' && c <= '9')
-          L= 10*L + c - '0';
+        {
+          if (L < 19999)
+            L= 10*L + c - '0';
+        }
         if (s - s1 > 8 || L > 19999)
           /* Avoid confusion from exponents
            * so large that e might overflow.