mysql - C++ stops connecting to DB after so many successful connects -

i using c++ write directly mysql database, program write first 151 items in data base gets number 152 fails connect data base , throws exact error:

unhandled exception @ 0x6188f1f9 (libmysql.dll) in project1.exe: 0xc0000005: access violation reading location 0x000003b0

i have no idea means , cannot seem find on internet it. below post code writes db. again though working fine until number 152.

void writetodb(string coordstring, string time, string id){ mysql *connect; // create pointer mysql instance connect=mysql_init(null); // initialise instance /* if irrelevant , don't need show it. kept in fault testing.*/ if(!connect)    /* if instance didn't initialize , exit fault.*/ {     fprintf(stderr,"mysql initialization failed");   } /* connect specific database.*/  connect=mysql_real_connect(connect,server,user,password,database,0,null,0); /* following if statements unneeded too, it's worth show on first app, if database empty or query didn't return @ least let know connection mysql server established. */  if(connect){     printf("connection succeeded\n"); } else{     printf("connection failed!\n");     return; } mysql_res *result; /* create pointer recieve return value.*/ mysql_row row;  /* assign variable rows. */ std::string strsql = "insert locationtime (id, datetime, location) values ('" + id + "','" + time + "','" + coordstring + "')";; const char* sql = strsql.c_str(); mysql_query(connect, sql); /* send query database. */  mysql_close(connect);   /* close , shutdown */   } 

edit: okay able stop throwing error, still mysteriously refusing connect db, did test php script instead , got 800+ values in table no issue @ all. im not sure issue @ all!

if mysql_real_connect() had failed should put return; or exit(1) after printf("connection failed!\n");:

if(connect) {     printf("connection succeeded\n"); } else {     printf("connection failed!\n");     return; // <<< } 

otherwise program crash, without see error notification printed.
check going wrong mysql_real_connect() function (and maybe give more useful information "connection failed!\n"), can use mysql_errno() function. list of error codes relevant function can found here.

another possibility passing invalid or empty data insert statements. put integrity checks data passed coordstring, time, id.