Re: stack overflow bug in ofstream::operator<<

[Corinna Vinschen <corinna-cygwin at cygwin dot com>]

On Jun 30 13:15, Corinna Vinschen wrote:
> inline bool
> check_alloca (size_t size)
> {
>   extern unsigned long _size_of_stack_reserve__;
>   register char *_curstack __asm__ ("%esp");
>   register size_t stacksize = pthread_self ()->attr.stacksize
>                               ?: (size_t) &_size_of_stack_reserve__;
>   return (size_t) ((_curstack - (_tlsbase - stacksize)) / 65536) * 65536 > size;
> }

No, that's incorrect since pthread_self ()->attr.stacksize doesn't
determine the stacksize of the current thread.

However, on reading MSDN again, I found that it's simpler than that.
We can savely assume that the thread's stack is *at least* as big as
__size_of_stack_reserve__.  See
http://msdn.microsoft.com/library/en-us/dllproc/base/thread_stack_size.asp

So the function can be simplified like this:

inline bool
check_alloca (size_t size)
{ 
  extern unsigned long _size_of_stack_reserve__;
  register char *_curstack __asm__ ("%esp");
  return (size_t) ((_curstack - (_tlsbase - (size_t) &_size_of_stack_reserve__))
                   / 65536) * 65536 > size;
}

Unfortunately SetThreadStackGuarantee() only exists beginning with 2K3 SP1.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          mailto:cygwin@cygwin.com
Red Hat, Inc.