*** stack smashing detected ***

[bilyed]

Hi everybody,

I have a program that reads the info into a file, check if this is in a mysql table and finally creates a new line or update it. Below it's a similar structure of my program (there are missing an structure and other variables...don't worry about them)

#include <iostream>
#include <string>
#include <mysql.h>
using namespace std;
int mysql_verify(int i);
int main()
{
    MYSQL *my;
    string id,info;
     int j;
    ifstream infile("mytext.txt");
    getline(infile,id);
    getline(infile,info);
    infile.close(infile);
    j = mysql_verify(id.c_str());

    .
    .
    .
    .
   /** and so on;**/
}
int mysql_verify(int id)
{
	MYSQL *my;
	my = mysql_init(NULL);
		if(my == NULL)
		{ 
			sprintf(error,"%s", mysql_error(my));
			cout<<"mysql: "<< error<<"\n";
	       exit (1);
	       
		}
		if(mysql_real_connect(my,myserver,myuser,mycpass,mydatabase,myport,NULL,0) == NULL )
		{
	   		sprintf(error,"%s",mysql_error(my));
			cout<<"mysql: "<<error<<"\n";
			exit (1);
		}
		char que[30];
		sprintf(que,"select * from smytable where id = \"%s%s\"\n",(mydcID).c_str(),id);
		if(mysql_query(my,que)){
					sprintf(error,"Mysql: %s\n",mysql_error(my));
					cout<<error;
					mysql_close(my);
				exit (1);
		}
		MYSQL_RES *res = mysql_store_result(my);
		i = mysql_num_rows(res);
		if( i > 1 )
		{
			cout<<"There are "<<i << " elements with ID: "<<myconn.dcID<<id<<"\n";
			mysql_close(my);
			exit (1);
		}
		mysql_close(my);
		return i;/***GDB says here is the problem**/
}/*****and also GDB says that the problem is here******/

My programs work from the command line or it's possible to give it the name of the file that will be read.

When I compile there is no any warning and of course error messages but when i run the program this give this output

*** stack smashing detected ***: ./dbw terminated
======= Backtrace: =========
/lib/tls/i686/cmov/libc.so.6(__fortify_fail+0x50)[0x82f390]
/lib/tls/i686/cmov/libc.so.6(+0xe233a)[0x82f33a]
./dbw(_Z12mysql_verifyPKc+0x338)[0x804e52d]
./dbw(main+0x442)[0x804a346]
/lib/tls/i686/cmov/libc.so.6(__libc_start_main+0xe6)[0x763bd6]
./dbw[0x8049e71]
.
.
.
.
.

I have been using GDB for finding where the problem is: from the gdb output frame :

(gdb) frame 6
#6  0x0804e52d in mysql_verify (id=0x806356c "20110312135645") at dbw.cpp:409
409	}
(gdb) print }
A syntax error in expression, near `}'.

and also there an issue in the return i;

I have checked out many times mysql_verify function and I don't find anything to suspect.

Any Ideas about those problems.

Thank you


Billy

[Athar]

You likely have invalid memory accesses somewhere, probably writing beyond array bounds.
Run the debug build of your program with valgrind, it will likely be able to tell you more.

[bilyed]

Hi Athar,

I have tried but there are too much information that I don't undertand completly.

Below it's an extract what i got when I run valgrind in this way

valgrind --tool=memcheck --leak-check=yes .-myprogram

==8378== LEAK SUMMARY:
==8378==    definitely lost: 0 bytes in 0 blocks
==8378==    indirectly lost: 0 bytes in 0 blocks
==8378==      possibly lost: 526 bytes in 19 blocks
==8378==    still reachable: 69,811 bytes in 21 blocks
==8378==         suppressed: 0 bytes in 0 blocks
==8378== Reachable blocks (those to which a pointer was found) are not shown.
==8378== To see them, rerun with: --leak-check=full --show-reachable=yes
==8378== 
==8378== For counts of detected and suppressed errors, rerun with: -v
==8378== ERROR SUMMARY: 19 errors from 19 contexts (suppressed: 27 from 10)
Aborted

any other idea please...

Thank you again,


Billy

[Athar]

That part of the valgrind output isn't particularly interesting, since you're not looking for memory leaks.
What you need to watch out for are messages like "Invalid write of size X at..." before the summary.

If that doesn't bring up anything, you could try defining the global macro _GLIBCXX_DEBUG.
However, that is only effective if you use the STL containers throughout your program, but you don't. Don't use sprintf or anything of the sort in a C++ program.

Ah right, talking about sprintf... here's your error:

char que[30];
sprintf(que,"select * from smytable where id = \"%s%s\"\n",(mydcID).c_str(),id);

This couldn't have happened if you had used std::string.

[moorecm]

By i, do you mean id?

[bilyed]

Hi Athar,

You're right...those sprintf functions have brought me only problem but I have a lot in my program and many are passed before to get this issue. Also I could check that the mysql query has been executed well.

I have changed to string type and it's the same problem and in the lines.........

[bilyed]

I have solved the problem changing the old c functions and using strings.

The lesson learnt is don't use old c function into a c++ program 'cause they can give you a lot of segmentation fault and other stuffs.