错误消息警告C4244 [英] Error Message Warning C4244

问题描述

收到有关数据类型的错误消息:
警告C4244:正在初始化":从"my_ulonglong"转换为"unsigned int"，可能丢失数据

Receiving an error message on data type:
warning C4244: ''initializing'' : conversion from ''my_ulonglong'' to ''unsigned int'', possible loss of data

int main()
   {
	MYSQL_RES *res_set;
	MYSQL* conn;
	MYSQL_ROW row;
   conn = mysql_init(NULL);
     if (mysql_real_connect(conn,"urlock.db.5513143.hostedresource.com","VendorCheck","Reader1234","urlock",0,NULL,0) !=0)
	 {
		mysql_query(conn,"SELECT * FROM tblURL WHERE ''192.168.1.1''");
		unsigned int i = 0;
		res_set = mysql_store_result(conn);
		unsigned int numrows = mysql_num_rows(res_set);
		while ((row = mysql_fetch_row(res_set)) != NULL){
		printf("%s\n",row[i] != NULL ?
        row[i] : "NULL");
		}
		mysql_free_result(res_set);
		mysql_close(conn);
		system("PAUSE"); 
	 }
	 else
	 {
		 cout << "Conn Failed!" <<endl;
     system("PAUSE"); 
     return 0;
	 }
}

推荐答案

mysql()调用之一可能返回类型my_ulonglong，通常类型"long long"的整数是64位整数，因此编译器告诉您，将"long long"整数的值放入常规的32位整数时，可能会丢失数据.如果您不希望结果超过32位整数的最大值，则只需执行显式强制转换以防止出现警告，否则，请将值传递给64位整数. br/>
显式演员表:

One of the mysql() calls is probably returning type my_ulonglong, usually a type "long long" integer is a 64-bit integer, so the compiler''s telling you that you may lose data when placing the value of a "long long" integer to a regular 32-bit integer. If you don''t expect the result to ever exceed the maximum value of a 32-bit integer, then just do an explicit cast to keep the warning from coming up, otherwise, pass the value onto a 64-bit integer instead.

Explicit Cast:

unsigned int val = (unsigned int) mysqlblah();

或将return int设置为64位int(两种选择):

Or set your return int to a 64-bit int (two alternatives):

unsigned long long val = mysqlblah();
unsigned __int64 val = mysqlblah();

这是参考页:
http://msdn.microsoft.com/en-us/library/s3f49ktz％28v = vs.80％29.aspx [ ^ ]

Here''s a reference page:
http://msdn.microsoft.com/en-us/library/s3f49ktz%28v=vs.80%29.aspx[^]

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