Bug #16102788: INDETERMINATE BEHAVIOR DUE TO EMPTY OPTION VALUES

Currently mysql programs silently accept empty strings as option values,
e.g. "--port=" will work the same as "--port=0" and -P "" will work the same as
-P 0.
This is unintuitive and can cause a lot of confusion.
Fixed the options collection code to throw an error if the explicit argument to 
an numeric or enum option is empty string.

Test case added.

mysql-test/r/mysql.result

@@ -518,5 +518,10 @@ ERROR 1243 (HY000) at line 15: Unknown prepared statement handler (x) given to E
 a
 1
 2
+#
+# Bug #16102788: INDETERMINATE BEHAVIOR DUE TO EMPTY OPTION VALUES
+#
+mysql: [ERROR] mysql: Empty value for 'port' specified
+mysql: [ERROR] mysql: Empty value for 'port' specified
 
 End of tests

mysql-test/suite/federated/federated_plugin-master.opt

@@ -1,2 +1,2 @@
---plugin_dir=$FEDERATED_PLUGIN_DIR
+$FEDERATED_PLUGIN_OPT
 --loose-federated=ON

mysql-test/t/mysql.test

@@ -631,5 +631,19 @@ EOF
 --exec $MYSQL < $MYSQLTEST_VARDIR/tmp/WL6797_cleanup.sql 2>&1
 --remove_file $MYSQLTEST_VARDIR/tmp/WL6797_cleanup.sql
 
+
+--echo #
+--echo # Bug #16102788: INDETERMINATE BEHAVIOR DUE TO EMPTY OPTION VALUES
+--echo #
+
+--replace_regex /mysql: .ERROR. [^ ]*: Empty value for 'port' specified/mysql: [ERROR] mysql: Empty value for 'port' specified/
+--error 5
+--exec $MYSQL --port= -e "SELECT 1" 2>&1
+
+--replace_regex /mysql: .ERROR. [^ ]*: Empty value for 'port' specified/mysql: [ERROR] mysql: Empty value for 'port' specified/
+--error 5
+--exec $MYSQL -P "" -e "SELECT 1" 2>&1
+
+
 --echo
 --echo End of tests

mysys_ssl/my_getopt.cc

@@ -709,10 +709,41 @@ static int setval(const struct my_option *opts, void *value, char *argument,
 {
   int err= 0, res= 0;
   bool error= 0;
+  ulong var_type= opts->var_type & GET_TYPE_MASK;
 
   if (!argument)
     argument= enabled_my_option;
 
+  /*
+    Thus check applies only to options that have a defined value
+    storage pointer.
+    We do it for numeric types only, as empty value is a valid
+    option for strings (the only way to reset back to default value).
+    Note: it does not relate to OPT_ARG/REQUIRED_ARG/NO_ARG, since
+    --param="" is not generally the same as --param.
+    TODO: Add an option definition flag to signify whether empty value
+    (i.e. --param="") is an acceptable value or an error and extend
+    the check to all options.
+  */
+  if (!*argument &&
+      (
+       var_type == GET_INT ||
+       var_type == GET_UINT ||
+       var_type == GET_LONG ||
+       var_type == GET_ULONG ||
+       var_type == GET_LL ||
+       var_type == GET_ULL ||
+       var_type == GET_DOUBLE ||
+       var_type == GET_ENUM
+      )
+     )
+  {
+    my_getopt_error_reporter(ERROR_LEVEL,
+                             "%s: Empty value for '%s' specified",
+                             my_progname, opts->name);
+    return EXIT_ARGUMENT_REQUIRED;
+  }
+
   if (value)
   {
     if (set_maximum_value && !(value= opts->u_max_value))
@@ -723,7 +754,7 @@ static int setval(const struct my_option *opts, void *value, char *argument,
       return EXIT_NO_PTR_TO_VARIABLE;
     }
 
-    switch ((opts->var_type & GET_TYPE_MASK)) {
+    switch (var_type) {
     case GET_BOOL: /* If argument differs from 0, enable option, else disable */
       *((my_bool*) value)= get_bool_argument(opts, argument, &error);
       if(error)