Error Message Warning C4244

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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;
	 }
}

Posted 10-May-11 16:36pm

Member 7766180

Updated 10-May-11 17:27pm

Hans Dietrich

v3

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Member 7766180 10-May-11 22:50pm

Am I going from a string to an integer? If so how to correct?
DS

1 solution

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Albert Holguin · Accepted Answer · 2011-05-10T17:17:00

Solution 1

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();

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

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

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

Posted 10-May-11 17:17pm

Albert Holguin

Updated 10-May-11 17:20pm

v2

Comments

Hans Dietrich 10-May-11 23:26pm

Accurate, complete answer. My 5.

Stefan_Lang 11-May-11 4:49am

Very good answer, but I'd put a heavy emphasis on "don't expect the result to _ever_ exceed". The history of the software industry, short as it is, is full of diastrous consequences of programmers believing a value would never exceed a certain limit, e. g.: "no one will ever need more than 640 KB memory", or: "two digits are enough to store a year".

Better be safe than sorry!

Albert Holguin 11-May-11 9:24am

its impossible to design with every single circumstance in mind, even now there's limitations ("...ever need more than 640...")... with that said, its up to everyone to make their own decisions

Member 7766180 11-May-11 10:50am

Thank you Albert! Great informative answer as usual! You are the best! You have helped and taught me several things in short period of time! You are true the spirit of this site! Onward! Where would I look in MySql() to find the 64bit call and what would it look like?
Thanks
DS

Albert Holguin 11-May-11 10:53am

thanks :) ... look at the function prototypes, the return type is the first portion of the prototype, a lot of libraries will make their own type names, but the definition would also be in the header with the rest of the prototypes.

Member 7766180 11-May-11 11:02am

Changed it to this and it works!
my_ulonglong i = 0;
res_set = mysql_store_result(conn);
my_ulonglong numrows = mysql_num_rows(res_set);
could it be the IP address field that is doing this?

Albert Holguin 11-May-11 11:05am

If that's all you changed and it works, then its likely mysql_num_rows() returning the 64bit number, makes sense, a database could have a really large number of entries