Re: I'm having a crashing problem with FreeTDS under OSX

As far as I can see the pointer looks ok as if I follow it using a  
printf I see a date format.
It's a really strange one!

Daniel

On 08/03/2009, at 3:10 AM, James K. Lowden wrote:

> Hi Daniel,
>
>> I put some printfs in around the free and it appears to be pointing  
>> to
>> a valid date format.
>
> That's interesting. I don't know anything about OS X heap management  
> or
> how an executable is arranged in memory.  My instinct says 0x16 is  
> too low
> for the heap, and free(3) seems to agree.
>
> Looking at the code, there are only a few places where data_fmt is  
> set,
> all of them output of calloc(3) or strdup(3).  I'm sure you see the  
> same
> yourself.  I don't see how FreeTDS could have set that pointer to  
> anything
> that can't be freed.
>
>> If I just comment out the free it then seems to fail on the next free
>> the code hits (and of course leaks;)
>> It is almost as if the heap is getting corrupted
>
> The OS X tool vmmap(1) might be of some help here.  I haven't used it
> myself but it's in the right neighborhood.
>
> I still suspect someone somewhere is trimming off the top 4 bytes of a
> pointer and then having a party.
>
> HTH.
>
> --jkl
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