Fix for bug#13934 Silent truncation of table comments

Table comment: issue a warning(error in traditional mode) if length of comment > 60 symbols
Column comment: issue a warning(error in traditional mode) if length of comment > 255 symbols
Table 'comment' is changed from char* to LEX_STRING

mysql-test/r/strict.result

@@ -1298,3 +1298,49 @@ t2	CREATE TABLE `t2` (
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t2,t1;
 set @@sql_mode= @org_mode;
+set @@sql_mode='traditional';
+create table t1 (i int)
+comment '123456789*123456789*123456789*123456789*123456789*
+         123456789*123456789*123456789*123456789*123456789*';
+ERROR HY000: Too long comment for table 't1'
+create table t1 (
+i int comment
+'123456789*123456789*123456789*123456789*
+ 123456789*123456789*123456789*123456789*
+ 123456789*123456789*123456789*123456789*
+ 123456789*123456789*123456789*123456789*
+ 123456789*123456789*123456789*123456789*
+ 123456789*123456789*123456789*123456789*
+ 123456789*123456789*123456789*123456789*');
+ERROR HY000: Too long comment for field 'i'
+set @@sql_mode= @org_mode;
+create table t1
+(i int comment
+'123456789*123456789*123456789*123456789*
+  123456789*123456789*123456789*123456789*
+  123456789*123456789*123456789*123456789*
+  123456789*123456789*123456789*123456789*
+  123456789*123456789*123456789*123456789*
+  123456789*123456789*123456789*123456789*
+  123456789*123456789*123456789*123456789*');
+Warnings:
+Warning	1105	Unknown error
+select column_name, column_comment from information_schema.columns where
+table_schema = 'test' and table_name = 't1';
+column_name	column_comment
+i	123456789*123456789*123456789*123456789*
+  123456789*123456789*123456789*123456789*
+  123456789*123456789*123456789*123456789*
+  123456789*123456789*123456789*123456789*
+  123456789*123456789*123456789*123456789*
+  123456789*123456789*123456789*123456789*
+drop table t1;
+set names utf8;
+create table t1 (i int)
+comment '123456789*123456789*123456789*123456789*123456789*123456789*';
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `i` int(11) default NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1 COMMENT='123456789*123456789*123456789*123456789*123456789*123456789*'
+drop table t1;

mysql-test/t/strict.test

@@ -1155,3 +1155,42 @@ create table t2 select date from t1;
 show create table t2;
 drop table t2,t1;
 set @@sql_mode= @org_mode;
+
+#
+# Bug #13934 Silent truncation of table comments
+#
+set @@sql_mode='traditional';
+--error 1105
+create table t1 (i int)
+comment '123456789*123456789*123456789*123456789*123456789*
+         123456789*123456789*123456789*123456789*123456789*';
+--error 1105
+create table t1 (
+i int comment
+'123456789*123456789*123456789*123456789*
+ 123456789*123456789*123456789*123456789*
+ 123456789*123456789*123456789*123456789*
+ 123456789*123456789*123456789*123456789*
+ 123456789*123456789*123456789*123456789*
+ 123456789*123456789*123456789*123456789*
+ 123456789*123456789*123456789*123456789*');
+set @@sql_mode= @org_mode;
+create table t1
+(i int comment
+ '123456789*123456789*123456789*123456789*
+  123456789*123456789*123456789*123456789*
+  123456789*123456789*123456789*123456789*
+  123456789*123456789*123456789*123456789*
+  123456789*123456789*123456789*123456789*
+  123456789*123456789*123456789*123456789*
+  123456789*123456789*123456789*123456789*');
+
+select column_name, column_comment from information_schema.columns where
+table_schema = 'test' and table_name = 't1';
+drop table t1;
+
+set names utf8;
+create table t1 (i int)
+comment '123456789*123456789*123456789*123456789*123456789*123456789*';
+show create table t1;
+drop table t1;

sql/handler.h

@@ -428,7 +428,8 @@ typedef struct st_ha_create_information
 {
   CHARSET_INFO *table_charset, *default_table_charset;
   LEX_STRING connect_string;
-  const char *comment,*password;
+  LEX_STRING comment;
+  const char *password;
   const char *data_file_name, *index_file_name;
   const char *alias;
   ulonglong max_rows,min_rows;

sql/sql_show.cc

@@ -1080,10 +1080,10 @@ store_create_info(THD *thd, TABLE_LIST *table_list, String *packet)
       packet->append(ha_row_type[(uint) share->row_type]);
     }
     table->file->append_create_info(packet);
-    if (share->comment && share->comment[0])
+    if (share->comment.length)
     {
       packet->append(STRING_WITH_LEN(" COMMENT="));
-      append_unescaped(packet, share->comment, strlen(share->comment));
+      append_unescaped(packet, share->comment.str, share->comment.length);
     }
     if (share->connect_string.length)
     {
@@ -2547,11 +2547,14 @@ static int get_schema_tables_record(THD *thd, struct st_table_list *tables,
                              (uint) (ptr-option_buff)-1), cs);
     {
       char *comment;
-      comment= show_table->file->update_table_comment(share->comment);
+      comment= show_table->file->update_table_comment(share->comment.str);
       if (comment)
       {
-        table->field[20]->store(comment, strlen(comment), cs);
-        if (comment != share->comment)
+        table->field[20]->store(comment,
+                                (comment == share->comment.str ?
+                                 share->comment.length : 
+                                 strlen(comment)), cs);
+        if (comment != share->comment.str)
           my_free(comment, MYF(0));
       }
     }

sql/sql_table.cc

@@ -3598,8 +3598,11 @@ bool mysql_alter_table(THD *thd,char *new_db, char *new_name,
     goto err;
   }
   create_info->db_type=new_db_type;
-  if (!create_info->comment)
-    create_info->comment= table->s->comment;
+  if (!create_info->comment.str)
+  {
+    create_info->comment.str= table->s->comment.str;
+    create_info->comment.length= table->s->comment.length;
+  }
 
   table->file->update_create_info(create_info);
   if ((create_info->table_options &

sql/sql_yacc.yy

@@ -2529,7 +2529,7 @@ create_table_option:
 	| MIN_ROWS opt_equal ulonglong_num	{ Lex->create_info.min_rows= $3; Lex->create_info.used_fields|= HA_CREATE_USED_MIN_ROWS;}
 	| AVG_ROW_LENGTH opt_equal ulong_num	{ Lex->create_info.avg_row_length=$3; Lex->create_info.used_fields|= HA_CREATE_USED_AVG_ROW_LENGTH;}
 	| PASSWORD opt_equal TEXT_STRING_sys	{ Lex->create_info.password=$3.str; Lex->create_info.used_fields|= HA_CREATE_USED_PASSWORD; }
-	| COMMENT_SYM opt_equal TEXT_STRING_sys	{ Lex->create_info.comment=$3.str; Lex->create_info.used_fields|= HA_CREATE_USED_COMMENT; }
+	| COMMENT_SYM opt_equal TEXT_STRING_sys	{ Lex->create_info.comment=$3; Lex->create_info.used_fields|= HA_CREATE_USED_COMMENT; }
 	| AUTO_INC opt_equal ulonglong_num	{ Lex->create_info.auto_increment_value=$3; Lex->create_info.used_fields|= HA_CREATE_USED_AUTO;}
         | PACK_KEYS_SYM opt_equal ulong_num
           {

sql/table.cc

@@ -410,7 +410,9 @@ int openfrm(THD *thd, const char *name, const char *alias, uint db_stat,
   int_length= uint2korr(head+274);
   share->null_fields= uint2korr(head+282);
   com_length= uint2korr(head+284);
-  share->comment= strdup_root(&outparam->mem_root, (char*) head+47);
+  share->comment.length=  (int) (head[46]);
+  share->comment.str= strmake_root(&outparam->mem_root, (char*) head+47,
+                                   share->comment.length);
 
   DBUG_PRINT("info",("i_count: %d  i_parts: %d  index: %d  n_length: %d  int_length: %d  com_length: %d", interval_count,interval_parts, share->keys,n_length,int_length, com_length));
 

sql/table.h

@@ -124,7 +124,7 @@ typedef struct st_table_share
 #endif
   uint	*blob_field;			/* Index to blobs in Field arrray*/
   byte	*default_values;		/* row with default values */
-  char	*comment;			/* Comment about table */
+  LEX_STRING comment;			/* Comment about table */
   CHARSET_INFO *table_charset;		/* Default charset of string fields */
 
   /* A pair "database_name\0table_name\0", widely used as simply a db name */

sql/unireg.cc

@@ -76,7 +76,7 @@ bool mysql_create_frm(THD *thd, my_string file_name,
 		      handler *db_file)
 {
   LEX_STRING str_db_type;
-  uint reclength,info_length,screens,key_info_length,maxlength;
+  uint reclength, info_length, screens, key_info_length, maxlength, tmp_len;
   ulong key_buff_length;
   File file;
   ulong filepos, data_offset;
@@ -143,10 +143,30 @@ bool mysql_create_frm(THD *thd, my_string file_name,
   fileinfo[26]= (uchar) test((create_info->max_rows == 1) &&
 			     (create_info->min_rows == 1) && (keys == 0));
   int2store(fileinfo+28,key_info_length);
-  strmake((char*) forminfo+47,create_info->comment ? create_info->comment : "",
-	  60);
-  forminfo[46]=(uchar) strlen((char*)forminfo+47);	// Length of comment
 
+  tmp_len= system_charset_info->cset->charpos(system_charset_info,
+                                              create_info->comment.str,
+                                              create_info->comment.str +
+                                              create_info->comment.length, 60);
+  if (tmp_len < create_info->comment.length)
+  {
+    char buff[128];
+    (void) my_snprintf(buff, sizeof(buff), "Too long comment for table '%s'",
+                       table);
+    if ((thd->variables.sql_mode &
+         (MODE_STRICT_TRANS_TABLES | MODE_STRICT_ALL_TABLES)))
+    {
+      my_message(ER_UNKNOWN_ERROR, buff, MYF(0));
+      goto err;
+    }
+    push_warning_printf(current_thd, MYSQL_ERROR::WARN_LEVEL_WARN,
+                        ER_UNKNOWN_ERROR, ER(ER_UNKNOWN_ERROR), buff);
+    create_info->comment.length= tmp_len;
+  }
+
+  strmake((char*) forminfo+47, create_info->comment.str ?
+          create_info->comment.str : "", create_info->comment.length);
+  forminfo[46]=(uchar) create_info->comment.length;
   if (my_pwrite(file,(byte*) fileinfo,64,0L,MYF_RW) ||
       my_pwrite(file,(byte*) keybuff,key_info_length,
 		(ulong) uint2korr(fileinfo+6),MYF_RW))
@@ -449,6 +469,27 @@ static bool pack_header(uchar *forminfo, enum db_type table_type,
   create_field *field;
   while ((field=it++))
   {
+
+    uint tmp_len= system_charset_info->cset->charpos(system_charset_info,
+                                                     field->comment.str,
+                                                     field->comment.str +
+                                                     field->comment.length, 255);
+    if (tmp_len < field->comment.length)
+    {
+      char buff[128];
+      (void) my_snprintf(buff,sizeof(buff), "Too long comment for field '%s'",
+                         field->field_name);
+      if ((current_thd->variables.sql_mode &
+	   (MODE_STRICT_TRANS_TABLES | MODE_STRICT_ALL_TABLES)))
+      {
+        my_message(ER_UNKNOWN_ERROR, buff, MYF(0));
+	DBUG_RETURN(1);
+      }
+      push_warning_printf(current_thd, MYSQL_ERROR::WARN_LEVEL_WARN,
+                          ER_UNKNOWN_ERROR, ER(ER_UNKNOWN_ERROR), buff);
+      field->comment.length= tmp_len;
+    }
+
     totlength+= field->length;
     com_length+= field->comment.length;
     if (MTYP_TYPENR(field->unireg_check) == Field::NOEMPTY ||