Fix for bug#19829:make test Failed in mysql_client_test

*with --with-charset=utf8*

Problem: wrong LONG TEXT field length is sent to a client 
when multibyte server character set used.

Fix: always limit field length sent to a client to 2^32,
as we store it in 4 byte slot.

Note: mysql_client_test changed accordingly.


sql/protocol.cc:
  Fix for bug#19829:make test Failed in mysql_client_test 
  *with --with-charset=utf8*
    - limit field length sent to client to UINT_MAX32 as 
      it may exceeds 32 bit slot for LONG TEXT fields if
      thd_charset->mbmaxlen > 1.
tests/mysql_client_test.c:
  Fix for bug#19829:make test Failed in mysql_client_test
  *with --with-charset=utf8*
    - checking field members have in mind that field length
      is limited to UINT_MAX32.

1 files changed, 16 insertions, 6 deletions

diff --git a/sql/protocol.cc b/sql/protocol.cc
index ff58d96f59b..2309bac88a9 100644
--- a/sql/protocol.cc
+++ b/sql/protocol.cc
@@ -616,7 +616,8 @@ bool Protocol::send_fields(List<Item> *list, uint flags)
       else
       {
         /* With conversion */
-        uint max_char_len;
+        ulonglong max_length;
+        uint32 field_length;
         int2store(pos, thd_charset->number);
         /*
           For TEXT/BLOB columns, field_length describes the maximum data
@@ -627,12 +628,21 @@ bool Protocol::send_fields(List<Item> *list, uint flags)
           char_count * mbmaxlen, where character count is taken from the
           definition of the column. In other words, the maximum number
           of characters here is limited by the column definition.
+
+          When one has a LONG TEXT column with a single-byte
+          character set, and the connection character set is multi-byte, the
+          client may get fields longer than UINT_MAX32, due to
+          <character set column> -> <character set connection> conversion.
+          In that case column max length does not fit into the 4 bytes
+          reserved for it in the protocol.
         */
-        max_char_len= (field.type >= (int) MYSQL_TYPE_TINY_BLOB &&
-                      field.type <= (int) MYSQL_TYPE_BLOB) ?
-                      field.length / item->collation.collation->mbminlen :
-                      field.length / item->collation.collation->mbmaxlen;
-        int4store(pos+2, max_char_len * thd_charset->mbmaxlen);
+        max_length= (field.type >= MYSQL_TYPE_TINY_BLOB &&
+                     field.type <= MYSQL_TYPE_BLOB) ?
+                     field.length / item->collation.collation->mbminlen :
+                     field.length / item->collation.collation->mbmaxlen;
+        max_length*= thd_charset->mbmaxlen;
+        field_length= (max_length > UINT_MAX32) ? UINT_MAX32 : max_length;
+        int4store(pos + 2, field_length);
       }
       pos[6]= field.type;
       int2store(pos+7,field.flags);