Truncations patch: a post-review fix.

include/mysql.h:
  Adding an option for data truncations feature.
libmysql/libmysql.c:
  No 'smart' behaviour now for data truncations: they are always
  reported, unless switched off with 
  mysql_options(mysql, MYSQL_REPORT_DATA_TRUNCATION, (my_bool*) &(option=1));
sql-common/client.c:
  Add support for report-data-truncation variable in my.cnf
tests/client_test.c:
  A test for MYSQL_REPORT_DATA_TRUNCATION option.

include/mysql.h

@@ -145,7 +145,8 @@ enum mysql_option
   MYSQL_OPT_PROTOCOL, MYSQL_SHARED_MEMORY_BASE_NAME, MYSQL_OPT_READ_TIMEOUT,
   MYSQL_OPT_WRITE_TIMEOUT, MYSQL_OPT_USE_RESULT,
   MYSQL_OPT_USE_REMOTE_CONNECTION, MYSQL_OPT_USE_EMBEDDED_CONNECTION,
-  MYSQL_OPT_GUESS_CONNECTION, MYSQL_SET_CLIENT_IP, MYSQL_SECURE_AUTH
+  MYSQL_OPT_GUESS_CONNECTION, MYSQL_SET_CLIENT_IP, MYSQL_SECURE_AUTH,
+  MYSQL_REPORT_DATA_TRUNCATION
 };
 
 struct st_mysql_options {
@@ -186,6 +187,8 @@ struct st_mysql_options {
   char *client_ip;
   /* Refuse client connecting to server if it uses old (pre-4.1.1) protocol */
   my_bool secure_auth;
+  /* 0 - never report, 1 - always report (default) */
+  my_bool report_data_truncation;
 
   /* function pointers for local infile support */
   int (*local_infile_init)(void **, const char *, void *);

libmysql/libmysql.c

@@ -4342,7 +4342,6 @@ my_bool STDCALL mysql_stmt_bind_result(MYSQL_STMT *stmt, MYSQL_BIND *bind)
   MYSQL_FIELD *field;
   ulong       bind_count= stmt->field_count;
   uint        param_count= 0;
-  uchar       report_data_truncation= 0;
   DBUG_ENTER("mysql_stmt_bind_result");
   DBUG_PRINT("enter",("field_count: %d", bind_count));
 
@@ -4380,8 +4379,6 @@ my_bool STDCALL mysql_stmt_bind_result(MYSQL_STMT *stmt, MYSQL_BIND *bind)
 
     if (!param->error)
       param->error= &param->error_value;
-    else
-      report_data_truncation= REPORT_DATA_TRUNCATION;
 
     param->param_number= param_count++;
     param->offset= 0;
@@ -4395,7 +4392,10 @@ my_bool STDCALL mysql_stmt_bind_result(MYSQL_STMT *stmt, MYSQL_BIND *bind)
       DBUG_RETURN(1);
     }
   }
-  stmt->bind_result_done= BIND_RESULT_DONE | report_data_truncation;
+  stmt->bind_result_done= BIND_RESULT_DONE;
+  if (stmt->mysql->options.report_data_truncation)
+    stmt->bind_result_done|= REPORT_DATA_TRUNCATION;
+
   DBUG_RETURN(0);
 }
 

sql-common/client.c

@@ -874,6 +874,7 @@ static const char *default_options[]=
   "replication-probe", "enable-reads-from-master", "repl-parse-query",
   "ssl-cipher", "max-allowed-packet", "protocol", "shared-memory-base-name",
   "multi-results", "multi-queries", "secure-auth",
+  "report-data-truncation",
   NullS
 };
 
@@ -1084,6 +1085,9 @@ void mysql_read_default_options(struct st_mysql_options *options,
         case 32: /* secure-auth */
           options->secure_auth= TRUE;
           break;
+        case 33: /* report-data-truncation */
+          options->report_data_truncation= opt_arg ? test(atoi(opt_arg)) : 1;
+          break;
 	default:
 	  DBUG_PRINT("warning",("unknown option: %s",option[0]));
 	}
@@ -1427,6 +1431,7 @@ mysql_init(MYSQL *mysql)
 #endif
 
   mysql->options.methods_to_use= MYSQL_OPT_GUESS_CONNECTION;
+  mysql->options.report_data_truncation= TRUE;  /* default */
   return mysql;
 }
 
@@ -2666,6 +2671,9 @@ mysql_options(MYSQL *mysql,enum mysql_option option, const char *arg)
   case MYSQL_SECURE_AUTH:
     mysql->options.secure_auth= *(my_bool *) arg;
     break;
+  case MYSQL_REPORT_DATA_TRUNCATION:
+    mysql->options.report_data_truncation= test(*(my_bool *) arg);
+    break;
   default:
     DBUG_RETURN(1);
   }

tests/client_test.c

@@ -12302,6 +12302,56 @@ static void test_truncation()
   myquery(rc);
 }
 
+static void test_truncation_option()
+{
+  MYSQL_STMT *stmt;
+  const char *stmt_text;
+  int rc;
+  uint8 buf;
+  my_bool option= 0;
+  my_bool error;
+  MYSQL_BIND bind;
+
+  myheader("test_truncation_option");
+
+  /* Prepare the test table */
+  stmt_text= "select -1";
+
+  stmt= mysql_stmt_init(mysql);
+  rc= mysql_stmt_prepare(stmt, stmt_text, strlen(stmt_text));
+  check_execute(stmt, rc);
+  rc= mysql_stmt_execute(stmt);
+  check_execute(stmt, rc);
+
+  bzero(&bind, sizeof(MYSQL_BIND));
+
+  bind.buffer= (void*) &buf;
+  bind.buffer_type= MYSQL_TYPE_TINY;
+  bind.is_unsigned= TRUE;
+  bind.error= &error;
+
+  rc= mysql_stmt_bind_result(stmt, &bind);
+  check_execute(stmt, rc);
+  rc= mysql_stmt_fetch(stmt);
+  DIE_UNLESS(rc == MYSQL_DATA_TRUNCATED);
+  DIE_UNLESS(error);
+  rc= mysql_options(mysql, MYSQL_REPORT_DATA_TRUNCATION, (char*) &option);
+  myquery(rc);
+  /* need to rebind for the new setting to take effect */
+  rc= mysql_stmt_bind_result(stmt, &bind);
+  check_execute(stmt, rc);
+  rc= mysql_stmt_execute(stmt);
+  check_execute(stmt, rc);
+  rc= mysql_stmt_fetch(stmt);
+  check_execute(stmt, rc);
+  /* The only change is rc - error pointers are still filled in */
+  DIE_UNLESS(error == 1);
+  /* restore back the defaults */
+  option= 1;
+  mysql_options(mysql, MYSQL_REPORT_DATA_TRUNCATION, (char*) &option);
+
+  mysql_stmt_close(stmt);
+}
 
 /*
   Read and parse arguments and MySQL options from my.cnf
@@ -12517,6 +12567,7 @@ static struct my_tests_st my_tests[]= {
   { "test_basic_cursors", test_basic_cursors },
   { "test_cursors_with_union", test_cursors_with_union },
   { "test_truncation", test_truncation },
+  { "test_truncation_option", test_truncation_option },
   { 0, 0 }
 };