Solved. Malplaced memset.... Op 07-01-2024 om 19:39 schreef Jogchum Reitsma via discuss:

Hi,

Using server version: 11.2.2, I try to extract data from a database with this C-code:

#include <stdlib.h> #include <stdio.h> #include <string.h> #include <mysql.h>

define MAXFLEN 66

char *bo_src = "SELECT FILENAMME, FILENUM FROM BOEK WHERE TOKENS IS NULL ORDER BY UDC_KOADE, FILENUM";

char   filename[MAXFLEN],        stavering[3];

long   filenum;

int fetch_result;

MYSQL      *bo_src_sql; MYSQL_ST MT *bo_src_stmt; MYSQL_RES  *bo_src_res; MYSQL_BIND  bo_src_bind[2],             bo_src_bind_result[2];

int main (argc, argv)

     int argc;   char *argv[];

  {  bo_src_sql = mysql_init(bo_src_sql)   ;  if ((bo_src_stmt = mysql_stmt_init(bo_src_sql))==NULL)         printf ("Can't initialize %s:\n %s/n", bo_src, mysql_error(bo_src_sql))   ;  if (!mysql_real_connect(bo_src_sql,"localhost","<user>","<passwd>","tdb",0,NULL,0))         fprintf(stderr, "Failed to connect to book table for select: Error: %s\n", mysql_error(bo_src_sql))   ; if (mysql_stmt_prepare(bo_src_stmt, bo_src, strlen(bo_src)))         printf ("Can't prepare %s:\n %s\n", bo_src, mysql_error(bo_src_sql))   ; bo_src_bind_result[0].buffer_type   = MYSQL_TYPE_STRING   ; bo_src_bind_result[0].buffer        = filename   ; bo_src_bind_result[0].buffer_length = 100   ; bo_src_bind_result[1].buffer_type   = MYSQL_TYPE_LONG   ; bo_src_bind_result[1].buffer        = (long *)&filenum   ; bo_src_bind_result[1].buffer_length = sizeof (filenum)   ;  memset (bo_src_bind, 0, sizeof (bo_src_bind))   ;  memset (bo_src_bind_result, 0, sizeof (bo_src_bind_result))   ;  if (mysql_stmt_bind_param (bo_src_stmt, bo_src_bind))        fprintf(stderr, "Failed to bind parameters in %s: \n Error: %s\n", bo_src, mysql_error(bo_src_sql))   ;  if (mysql_stmt_bind_result(bo_src_stmt, bo_src_bind_result))        fprintf(stderr, "Failed to bind result in %s: \n Error: %s\n", bo_src, mysql_error(bo_src_sql))   ;  if (!mysql_stmt_execute (bo_src_stmt))         {  fetch_result = mysql_stmt_fetch(bo_src_stmt)         ;  if  (fetch_result == 0)                 printf ("%ld %s %s\n", filenum, filename, stavering)         ;  else if (fetch_result == MYSQL_NO_DATA)                     printf ("No data found\n")         ;       else if (fetch_result == MYSQL_DATA_TRUNCATED)                          printf ("Data truncated.\n%d/n", fetch_result)         ;            else printf ("Something else! %d \n%s/n", fetch_result, mysql_error(bo_src_sql));         }   ;  mysql_stmt_close(bo_src_stmt)   ;  mysql_close(bo_src_sql);   }

The definition of the table is

describe BOEK; +-----------+-------------------------------+------+-----+---------+----------------+

| Field     | Type                          | Null | Key | Default | Extra          | +-----------+-------------------------------+------+-----+---------+----------------+

| FILENUM   | smallint(4)                   | NO   | PRI | NULL    | auto_increment | | TITEL     | varchar(50)                   | YES  |     | NULL    |                | | UDC_KOADE | varchar(10)                   | YES  |     | NULL    |                | | ISBN      | bigint(13)                    | YES  |     | NULL    |                | | FILENAMME | varchar(20)                   | YES  |     | NULL    |                | | SKR_NUM   | smallint(5)                   | YES  |     | NULL    |                | | UTJ_NUM   | smallint(5)                   | YES  |     | NULL    |                | | UTJ_DATUM | date                          | YES  |     | NULL    |                | | OERSET    | tinyint(1)                    | YES  |     | NULL    |                | | PRINTINGE | smallint(3)                   | YES  |     | NULL    |                | | YNL_DATUM | date                          | YES  |     | NULL    |                | | STAVERING | enum('ald','mid','nij','int') | YES  |     | NULL    |                | | TOKENS    | smallint(6)                   | YES  |     | NULL    |                | | TYPES     | smallint(5)                   | YES  |     | NULL    |                | | MAXTOKENS | smallint(6)                   | YES  |     | NULL    |                | | MAXTYPES  | smallint(5)                   | YES  |     | NULL    |                | | TIID      | time                          | YES  |     | NULL    |                | +-----------+-------------------------------+------+-----+---------+----------------+

So the size of FILENAMME, varchar20, is much smaller than the buffer length specified in the code:

  ; bo_src_bind_result[0].buffer_type   = MYSQL_TYPE_STRING   ; bo_src_bind_result[0].buffer        = filename   ; bo_src_bind_result[0].buffer_length = 100

Yet I get a MYSQL_DATA_TRUNCATED fetching the result of the query.

Debugging, only the integer filenum gets its value.

The statement (SELECT FILENAMME, FILENUM FROM BOEK WHERE TOKENS IS NULL ORDER BY UDC_KOADE, FILENUM;) gives the expected result when entered in a terminal session.

I obviously do something wrong, but I can't find out what. Googling gets me no answer.

Anyone who can spot the error?

Many thanks in advance,

best regards, Jogchum

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