MDEV-34295 CAST(char_col AS DOUBLE) prints redundant spaces in a warning

Field_string::val_int(), Field_string::val_real(), Field_string::val_decimal()
passed the whole buffer of field_length bytes to data type conversion routines.
This made conversion routines to print redundant trailing spaces in case of warnings.

Adding a method Field_string::to_lex_cstring() and using it inside
val_int(), val_real(), val_decimal(), val_str().

After this change conversion routines get the same value with what val_str() returns,
and no redundant trailing spaces are displayed.

mysql-test/main/type_char.result

@@ -0,0 +1,40 @@
+#
+# Start of 10.5 tests
+#
+#
+# MDEV-34295 CAST(char_col AS DOUBLE) prints redundant spaces in a warning
+#
+CREATE TABLE t1 (a CHAR(5) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci);
+INSERT INTO t1 VALUES ('1x'), ('x');
+SELECT a, CAST(a AS DOUBLE) FROM t1 ORDER BY a;
+a	CAST(a AS DOUBLE)
+1x	1
+x	0
+Warnings:
+Warning	1292	Truncated incorrect DOUBLE value: '1x'
+Warning	1292	Truncated incorrect DOUBLE value: 'x'
+SELECT a, CAST(a AS DECIMAL(20,2)) FROM t1 ORDER BY a;
+a	CAST(a AS DECIMAL(20,2))
+1x	1.00
+x	0.00
+Warnings:
+Warning	1292	Truncated incorrect DECIMAL value: '1x'
+Warning	1292	Truncated incorrect DECIMAL value: 'x'
+SELECT a, CAST(a AS SIGNED) FROM t1 ORDER BY a;
+a	CAST(a AS SIGNED)
+1x	1
+x	0
+Warnings:
+Warning	1292	Truncated incorrect INTEGER value: '1x'
+Warning	1292	Truncated incorrect INTEGER value: 'x'
+SELECT a, CAST(a AS UNSIGNED) FROM t1 ORDER BY a;
+a	CAST(a AS UNSIGNED)
+1x	1
+x	0
+Warnings:
+Warning	1292	Truncated incorrect INTEGER value: '1x'
+Warning	1292	Truncated incorrect INTEGER value: 'x'
+DROP TABLE t1;
+#
+# End of 10.5 tests
+#

mysql-test/main/type_char.test

@@ -0,0 +1,19 @@
+--echo #
+--echo # Start of 10.5 tests
+--echo #
+
+--echo #
+--echo # MDEV-34295 CAST(char_col AS DOUBLE) prints redundant spaces in a warning
+--echo #
+
+CREATE TABLE t1 (a CHAR(5) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci);
+INSERT INTO t1 VALUES ('1x'), ('x');
+SELECT a, CAST(a AS DOUBLE) FROM t1 ORDER BY a;
+SELECT a, CAST(a AS DECIMAL(20,2)) FROM t1 ORDER BY a;
+SELECT a, CAST(a AS SIGNED) FROM t1 ORDER BY a;
+SELECT a, CAST(a AS UNSIGNED) FROM t1 ORDER BY a;
+DROP TABLE t1;
+
+--echo #
+--echo # End of 10.5 tests
+--echo #

sql/field.cc

@@ -7485,11 +7485,11 @@ double Field_string::val_real(void)
 {
   DBUG_ASSERT(marked_for_read());
   THD *thd= get_thd();
-  return Converter_strntod_with_warn(get_thd(),
+  const LEX_CSTRING str= to_lex_cstring();
+  return Converter_strntod_with_warn(thd,
                                      Warn_filter_string(thd, this),
                                      Field_string::charset(),
-                                     (const char *) ptr,
+                                     str.str, str.length).result();
-                                     field_length).result();
 }
 
 
@@ -7497,10 +7497,10 @@ longlong Field_string::val_int(void)
 {
   DBUG_ASSERT(marked_for_read());
   THD *thd= get_thd();
+  const LEX_CSTRING str= to_lex_cstring();
   return Converter_strntoll_with_warn(thd, Warn_filter_string(thd, this),
                                       Field_string::charset(),
-                                      (const char *) ptr,
+                                      str.str, str.length).result();
-                                      field_length).result();
 }
 
 
@@ -7516,20 +7516,26 @@ sql_mode_t Field_string::can_handle_sql_mode_dependency_on_store() const
 }
 
 
-String *Field_string::val_str(String *val_buffer __attribute__((unused)),
+LEX_CSTRING Field_string::to_lex_cstring() const
-			      String *val_ptr)
 {
   DBUG_ASSERT(marked_for_read());
   /* See the comment for Field_long::store(long long) */
   DBUG_ASSERT(!table || table->in_use == current_thd);
-  size_t length;
+  if (get_thd()->variables.sql_mode & MODE_PAD_CHAR_TO_FULL_LENGTH)
-  if (get_thd()->variables.sql_mode &
+    return Lex_cstring((const char*) ptr,
-      MODE_PAD_CHAR_TO_FULL_LENGTH)
+                       field_charset()->charpos(ptr, ptr + field_length,
-    length= field_charset()->charpos(ptr, ptr + field_length,
+                                                Field_string::char_length()));
-                                     Field_string::char_length());
+  return Lex_cstring((const char *) ptr,
-  else
+                     field_charset()->lengthsp((const char*) ptr, field_length));
-    length= field_charset()->lengthsp((const char*) ptr, field_length);
+}
-  val_ptr->set((const char*) ptr, length, field_charset());
+
+
+String *Field_string::val_str(String *val_buffer __attribute__((unused)),
+			      String *val_ptr)
+{
+  DBUG_ASSERT(marked_for_read());
+  const LEX_CSTRING str= to_lex_cstring();
+  val_ptr->set(str.str, str.length, field_charset());
   return val_ptr;
 }
 
@@ -7538,12 +7544,12 @@ my_decimal *Field_string::val_decimal(my_decimal *decimal_value)
 {
   DBUG_ASSERT(marked_for_read());
   THD *thd= get_thd();
+  const LEX_CSTRING str= to_lex_cstring();
   Converter_str2my_decimal_with_warn(thd,
                                      Warn_filter_string(thd, this),
                                      E_DEC_FATAL_ERROR & ~E_DEC_BAD_NUM,
                                      Field_string::charset(),
-                                     (const char *) ptr,
+                                     str.str, str.length, decimal_value);
-                                     field_length, decimal_value);
   return decimal_value;
 }
 

sql/field.h

@@ -4013,6 +4013,7 @@ class Field_string final :public Field_longstr {
            field_length >= 4 &&
            orig_table->s->frm_version < FRM_VER_TRUE_VARCHAR;
   }
+  LEX_CSTRING to_lex_cstring() const;
 public:
   bool can_alter_field_type;
   Field_string(uchar *ptr_arg, uint32 len_arg,uchar *null_ptr_arg,