[K42-discussion] Thread object destructor

[Bryan S Rosenburg]

Donour Sizemore wrote on 07/15/2006 05:01:40 PM:
> Does anybody know why adding a destructor to the base thread object 
> (Thread) would cause the things to overrun the stack fence? According to 

> strategically placed err_printf's, the destructor is never actually 
> getting called.

The base Thread class has no virtual methods, so adding a virtual 
destructor causes the class to have a vtable pointer where it didn't 
before.  The "attachment" field may then no longer be the very first word 
of the structure.  Code in the Linux module that we import into K42 
requires that the attachment field be the first word.  This requirement is 
documented (but unfortunately not enforced) in 
lib/libc/scheduler/Thread.H.  I'm guessing that your stack overflow is a 
consequence of violating this assumption.  Do you really need a virtual 
destructor in class Thread?

- Bryan

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