Re: -[NSData initWithContentsOfMappedFile:] crash if MMAP is present

[Richard Frith-Macdonald]

On Thursday, March 6, 2003, at 01:03  pm, Roland Schwingel wrote:

> Hi...
>
> I discovered a crash in NSData...

Thanks ... I fixed it in the 1.6.0 branch of CVS

> Imagine MMAP is defined. I wonder how this could ever have
> worked. It crashes for me (of course) self is released before the
> zone is taken from it.

It would work because, GSObjCZone() would get the zone from an offset 
against the address of self, and generally while deallocating self will 
have returned the memory to the memory allocation system, it will not 
have been overwritten and will therefore still contain the correct 
pointer to the zone.

In general, method calls on a deallocated object will crash because the 
deallocation process overwrites the 'isa' pointer in the object, which 
is used to locate the method implementation to be used.  Direct 
accesses into the rest of the memory of a (very) recently deallocated 
object will often/usually work.