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List:       mysql-plusplus
Subject:    Access Violation without crash
From:       Patrice BEAUJOLIN <pbeaujolin () alex ! fr>
Date:       2001-06-26 12:57:21
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Hi all !
I've got a strange behaviour when running the simpliest sample program
in debug (step by step) mode
System:
Win NT4 sp5
MSVC++ 6.0 (not patched)
mysql++ lib recompiled in multithread mode (same behaviour with original lib)

When I don't make any reference to the 'row' variable everything works fine.
As soon as I attempt an access (i.e. adding dateTime = row[1];  ), I've got an
0xC0000005: Access Violation error message on the 'try' instruction (in the \
disassembly  code, just after line 23) but the progrom does not crash. Resuming from \
this error take up to 30 seconds but is OK.

When Executing the program (no step by step), everything is just fine.

Is this behaviour a normal one, or what am I doing wrong?
Any suggestion would be greatly appreciated.
Thanks for your attention

Here is the code :
#include "windows.h"
#pragma warning(disable: 4786) 
#pragma warning(disable: 4800)

#define MYSQL_NO_SHORT_NAMES

#include "sqlplus.hh"

using namespace std;


int main(int argc, char* argv[])
{

  try { // its in one big try block 
  
    MysqlRes::iterator i;
	Row		row;
	MysqlRes				sqlResult;
	MysqlDateTime			dateTime;
	  
	MysqlConnection con(mysql_use_exceptions); 
	con.connect(DB_NAME, DB_HOST, DB_USER, DB_PWD); 

    MysqlQuery query = con.query(); 
    
    query << "select * from action";
    sqlResult = query.store(); 

    for (i = sqlResult.begin(); i != sqlResult.end(); i++) { 
	
      row = *i; 
	  
	  dateTime = row[1];	  
     } 

	return 0;
 

  } catch (MysqlBadQuery er) { // handle any connection or 
                          // query errors that may come up 
	printf("Query Error\n");
    return -1; 

  } catch (MysqlBadConversion er) { // handle bad conversions 
    printf("Conversion Error\n");
    return -2; 
  } 

}

Here is the disassembly code part:
20:   int main(int argc, char* argv[])
21:   {
00401FC0   push        ebp
00401FC1   mov         ebp,esp
00401FC3   push        0FFh
00401FC5   push        offset __ehhandler$_main (00463c42)
00401FCA   mov         eax,fs:[00000000]
00401FD0   push        eax
00401FD1   mov         dword ptr fs:[0],esp
00401FD8   push        ecx
00401FD9   sub         esp,570h
00401FDF   push        ebx
00401FE0   push        esi
00401FE1   push        edi
00401FE2   mov         dword ptr [ebp-10h],esp
00401FE5   lea         edi,[ebp-580h]
00401FEB   mov         ecx,15Ch
00401FF0   mov         eax,0CCCCCCCCh
00401FF5   rep stos    dword ptr [edi]
22:
23:     try { // its in one big try block
00401FF7   mov         dword ptr [ebp-4],0                           \
<------------------- Here is the access violation 24:
25:       char c;
26:       MysqlRes::iterator i;
00401FFE   lea         ecx,[i]
00402001   call        \
@ILT+1525(subscript_iterator<const_subscript_container<MysqlRes,MysqlRow,MysqlRow \
const

Best regards,

Patrice BEAUJOLIN
Software Engineer
----------------------
Alex Temex Multimedia S.A.
4 Bis, Avenue du pré de Challes
74940 Annecy le vieux - FRANCE
Phone : +33 (0) 4 50 64 08 97
Fax   : +33 (0) 4 50 64 09 02
email : pbeaujolin@alex.fr
http://www.alex.com


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