[asterisk-dev] cdr_odbc.c is broken in trunk

[Nick Gorham]

Tilghman Lesher wrote:

>On Thursday 10 January 2008 08:06:20 Nick Gorham wrote:
>  
>
>>Michiel van Baak wrote:
>>    
>>
>>>On 11:18, Thu 10 Jan 08, Nick Gorham wrote:
>>>      
>>>
>>>>Hi,
>>>>
>>>>The change to use prepare_cb() in odbc_log became broken in r88182.
>>>>
>>>>The code calls SQLBindParameter on a local variable (timestr) but as it
>>>>now doesn't call SQLExecute in the same function when it finally gets to
>>>>SQLExecute that variable is out of scope.
>>>>        
>>>>
>
>Out of scope, perhaps, but not out of memory.  It's stored on the local stack,
>which is not deallocated until after the function returns.  The address thus
>remains valid.
>  
>

Using what I think you are suggesting is good coding, the following 
shows, that how the memory can be overwritten.

#include <stdio.h>

char *saved_ptr;

void do_something_else( void )
{
    char another_big_buffer[ 1024 ];   /* this time its there to ensure 
we know ehere we are writing
                                                    * instead of just 
some random location
                                                    */
    char other_txt[ 20 ];

    strcpy( other_txt, "BANG!!!!" );
}

void set_the_memory( void )
{
    char big_buffer[ 1024 ];    /* only there to make sure that the 
printf in the
                                 * calling code doesn't itself overrite 
the buffer
                                 */
    char txt[ 20 ];

    strcpy( txt, "hello world" );

    saved_ptr = txt;
}

void expect_the_memory_to_remain( void )
{
    printf( "the memory contains '%s'\n", saved_ptr );
}

main()
{
    set_the_memory();

    do_something_else();

    expect_the_memory_to_remain();
}

-- 
Nick Gorham